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Message-Id: <20240407084319.1462211-3-mingo@kernel.org>
Date: Sun, 7 Apr 2024 10:43:16 +0200
From: Ingo Molnar <mingo@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Shrikanth Hegde <sshegde@...ux.ibm.com>,
Valentin Schneider <vschneid@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 2/5] sched: Split out kernel/sched/fair_balance.c from kernel/sched/fair.c
Move the SMP load-balancing code into the new fair_balance.c file,
because it's mostly self-contained code that comprised about 50% of
the lines of code in fair.c.
Expose the sched_balance_softirq(), sched_balance_find_dst_group(),
cpu_load_without(), cpu_runnable_without(), cpu_util_without(),
sched_balance_newidle(), task_h_load(), throttled_lb_pair(),
task_util(), task_util_est() and a number of other methods
internally to better facilitate this code separation.
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
kernel/sched/Makefile | 1 +
kernel/sched/core.c | 1 +
kernel/sched/fair.c | 10366 +++++++++++++++-----------------------------------------------
kernel/sched/fair_balance.c | 5103 +++++++++++++++++++++++++++++++
kernel/sched/sched.h | 256 ++
5 files changed, 7909 insertions(+), 7818 deletions(-)
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index c7afe445480a..898f6062a2a7 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -31,5 +31,6 @@ endif
obj-y += core.o
obj-y += syscalls.o
obj-y += fair.o
+obj-y += fair_balance.o
obj-y += build_policy.o
obj-y += build_utility.o
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7fbb53d27229..013ce552941a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8337,6 +8337,7 @@ void __init sched_init(void)
balance_push_set(smp_processor_id(), false);
#endif
init_sched_fair_class();
+ init_sched_fair_class_balance();
psi_init();
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1dd37168da50..9eba1c4e2a00 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -91,31 +91,6 @@ static int __init setup_sched_thermal_decay_shift(char *str)
}
__setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
-#ifdef CONFIG_SMP
-/*
- * For asym packing, by default the lower numbered CPU has higher priority.
- */
-int __weak arch_asym_cpu_priority(int cpu)
-{
- return -cpu;
-}
-
-/*
- * The margin used when comparing utilization with CPU capacity.
- *
- * (default: ~20%)
- */
-#define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024)
-
-/*
- * The margin used when comparing CPU capacities.
- * is 'cap1' noticeably greater than 'cap2'
- *
- * (default: ~5%)
- */
-#define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078)
-#endif
-
#ifdef CONFIG_CFS_BANDWIDTH
/*
* Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
@@ -309,10 +284,6 @@ const struct sched_class fair_sched_class;
#ifdef CONFIG_FAIR_GROUP_SCHED
-/* Walk up scheduling entities hierarchy */
-#define for_each_sched_entity(se) \
- for (; se; se = se->parent)
-
static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
struct rq *rq = rq_of(cfs_rq);
@@ -381,7 +352,7 @@ static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
return false;
}
-static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
+void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
if (cfs_rq->on_list) {
struct rq *rq = rq_of(cfs_rq);
@@ -406,11 +377,6 @@ static inline void assert_list_leaf_cfs_rq(struct rq *rq)
SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
}
-/* Iterate through all leaf cfs_rq's on a runqueue */
-#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
- list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
- leaf_cfs_rq_list)
-
/* Do the two (enqueued) entities belong to the same group ? */
static inline struct cfs_rq *
is_same_group(struct sched_entity *se, struct sched_entity *pse)
@@ -477,25 +443,15 @@ static int se_is_idle(struct sched_entity *se)
#else /* !CONFIG_FAIR_GROUP_SCHED */
-#define for_each_sched_entity(se) \
- for (; se; se = NULL)
-
static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
return true;
}
-static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
-{
-}
-
static inline void assert_list_leaf_cfs_rq(struct rq *rq)
{
}
-#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
- for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
-
static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
return NULL;
@@ -1005,8 +961,6 @@ static void update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se)
#ifdef CONFIG_SMP
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
-static unsigned long task_h_load(struct task_struct *p);
-static unsigned long capacity_of(int cpu);
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
@@ -1098,9 +1052,6 @@ void init_entity_runnable_average(struct sched_entity *se)
void post_init_entity_util_avg(struct task_struct *p)
{
}
-static void update_tg_load_avg(struct cfs_rq *cfs_rq)
-{
-}
#endif /* CONFIG_SMP */
static s64 update_curr_se(struct rq *rq, struct sched_entity *curr)
@@ -1305,7 +1256,8 @@ update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
* Scheduling class queueing methods:
*/
-static inline bool is_core_idle(int cpu)
+#ifdef CONFIG_SMP
+bool is_core_idle(int cpu)
{
#ifdef CONFIG_SCHED_SMT
int sibling;
@@ -1321,12 +1273,12 @@ static inline bool is_core_idle(int cpu)
return true;
}
+#endif
#ifdef CONFIG_NUMA
#define NUMA_IMBALANCE_MIN 2
-static inline long
-adjust_numa_imbalance(int imbalance, int dst_running, int imb_numa_nr)
+long adjust_numa_imbalance(int imbalance, int dst_running, int imb_numa_nr)
{
/*
* Allow a NUMA imbalance if busy CPUs is less than the maximum
@@ -1670,8 +1622,7 @@ static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
* larger multiplier, in order to group tasks together that are almost
* evenly spread out between numa nodes.
*/
-static inline unsigned long task_weight(struct task_struct *p, int nid,
- int dist)
+unsigned long task_weight(struct task_struct *p, int nid, int dist)
{
unsigned long faults, total_faults;
@@ -1689,8 +1640,7 @@ static inline unsigned long task_weight(struct task_struct *p, int nid,
return 1000 * faults / total_faults;
}
-static inline unsigned long group_weight(struct task_struct *p, int nid,
- int dist)
+unsigned long group_weight(struct task_struct *p, int nid, int dist)
{
struct numa_group *ng = deref_task_numa_group(p);
unsigned long faults, total_faults;
@@ -1982,7 +1932,6 @@ struct task_numa_env {
};
static unsigned long cpu_load(struct rq *rq);
-static unsigned long cpu_runnable(struct rq *rq);
static inline enum
numa_type numa_classify(unsigned int imbalance_pct,
@@ -3604,77 +3553,113 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
cfs_rq->idle_nr_running--;
}
-/*
- * Signed add and clamp on underflow.
- *
- * Explicitly do a load-store to ensure the intermediate value never hits
- * memory. This allows lockless observations without ever seeing the negative
- * values.
- */
-#define add_positive(_ptr, _val) do { \
- typeof(_ptr) ptr = (_ptr); \
- typeof(_val) val = (_val); \
- typeof(*ptr) res, var = READ_ONCE(*ptr); \
- \
- res = var + val; \
- \
- if (val < 0 && res > var) \
- res = 0; \
- \
- WRITE_ONCE(*ptr, res); \
-} while (0)
+static void
+place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
+{
+ u64 vslice, vruntime = avg_vruntime(cfs_rq);
+ s64 lag = 0;
-/*
- * Unsigned subtract and clamp on underflow.
- *
- * Explicitly do a load-store to ensure the intermediate value never hits
- * memory. This allows lockless observations without ever seeing the negative
- * values.
- */
-#define sub_positive(_ptr, _val) do { \
- typeof(_ptr) ptr = (_ptr); \
- typeof(*ptr) val = (_val); \
- typeof(*ptr) res, var = READ_ONCE(*ptr); \
- res = var - val; \
- if (res > var) \
- res = 0; \
- WRITE_ONCE(*ptr, res); \
-} while (0)
+ se->slice = sysctl_sched_base_slice;
+ vslice = calc_delta_fair(se->slice, se);
-/*
- * Remove and clamp on negative, from a local variable.
- *
- * A variant of sub_positive(), which does not use explicit load-store
- * and is thus optimized for local variable updates.
- */
-#define lsub_positive(_ptr, _val) do { \
- typeof(_ptr) ptr = (_ptr); \
- *ptr -= min_t(typeof(*ptr), *ptr, _val); \
-} while (0)
+ /*
+ * Due to how V is constructed as the weighted average of entities,
+ * adding tasks with positive lag, or removing tasks with negative lag
+ * will move 'time' backwards, this can screw around with the lag of
+ * other tasks.
+ *
+ * EEVDF: placement strategy #1 / #2
+ */
+ if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) {
+ struct sched_entity *curr = cfs_rq->curr;
+ unsigned long load;
-#ifdef CONFIG_SMP
-static inline void
-enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
- cfs_rq->avg.load_avg += se->avg.load_avg;
- cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
-}
+ lag = se->vlag;
-static inline void
-dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
- sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
- sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
- /* See update_cfs_rq_load_avg() */
- cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum,
- cfs_rq->avg.load_avg * PELT_MIN_DIVIDER);
+ /*
+ * If we want to place a task and preserve lag, we have to
+ * consider the effect of the new entity on the weighted
+ * average and compensate for this, otherwise lag can quickly
+ * evaporate.
+ *
+ * Lag is defined as:
+ *
+ * lag_i = S - s_i = w_i * (V - v_i)
+ *
+ * To avoid the 'w_i' term all over the place, we only track
+ * the virtual lag:
+ *
+ * vl_i = V - v_i <=> v_i = V - vl_i
+ *
+ * And we take V to be the weighted average of all v:
+ *
+ * V = (\Sum w_j*v_j) / W
+ *
+ * Where W is: \Sum w_j
+ *
+ * Then, the weighted average after adding an entity with lag
+ * vl_i is given by:
+ *
+ * V' = (\Sum w_j*v_j + w_i*v_i) / (W + w_i)
+ * = (W*V + w_i*(V - vl_i)) / (W + w_i)
+ * = (W*V + w_i*V - w_i*vl_i) / (W + w_i)
+ * = (V*(W + w_i) - w_i*l) / (W + w_i)
+ * = V - w_i*vl_i / (W + w_i)
+ *
+ * And the actual lag after adding an entity with vl_i is:
+ *
+ * vl'_i = V' - v_i
+ * = V - w_i*vl_i / (W + w_i) - (V - vl_i)
+ * = vl_i - w_i*vl_i / (W + w_i)
+ *
+ * Which is strictly less than vl_i. So in order to preserve lag
+ * we should inflate the lag before placement such that the
+ * effective lag after placement comes out right.
+ *
+ * As such, invert the above relation for vl'_i to get the vl_i
+ * we need to use such that the lag after placement is the lag
+ * we computed before dequeue.
+ *
+ * vl'_i = vl_i - w_i*vl_i / (W + w_i)
+ * = ((W + w_i)*vl_i - w_i*vl_i) / (W + w_i)
+ *
+ * (W + w_i)*vl'_i = (W + w_i)*vl_i - w_i*vl_i
+ * = W*vl_i
+ *
+ * vl_i = (W + w_i)*vl'_i / W
+ */
+ load = cfs_rq->avg_load;
+ if (curr && curr->on_rq)
+ load += scale_load_down(curr->load.weight);
+
+ lag *= load + scale_load_down(se->load.weight);
+ if (WARN_ON_ONCE(!load))
+ load = 1;
+ lag = div_s64(lag, load);
+ }
+
+ se->vruntime = vruntime - lag;
+
+ /*
+ * When joining the competition; the existing tasks will be,
+ * on average, halfway through their slice, as such start tasks
+ * off with half a slice to ease into the competition.
+ */
+ if (sched_feat(PLACE_DEADLINE_INITIAL) && (flags & ENQUEUE_INITIAL))
+ vslice /= 2;
+
+ /*
+ * EEVDF: vd_i = ve_i + r_i/w_i
+ */
+ se->deadline = se->vruntime + vslice;
}
-#else
-static inline void
-enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
-static inline void
-dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
-#endif
+
+static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
+static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq);
+
+static inline bool cfs_bandwidth_used(void);
+
+static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
static void reweight_eevdf(struct cfs_rq *cfs_rq, struct sched_entity *se,
unsigned long weight)
@@ -3783,6 +3768,7 @@ static void reweight_eevdf(struct cfs_rq *cfs_rq, struct sched_entity *se,
se->deadline = avruntime + vslice;
}
+
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
unsigned long weight)
{
@@ -3846,8 +3832,6 @@ void reweight_task(struct task_struct *p, int prio)
load->inv_weight = sched_prio_to_wmult[prio];
}
-static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
-
#ifdef CONFIG_FAIR_GROUP_SCHED
#ifdef CONFIG_SMP
/*
@@ -3988,8534 +3972,3292 @@ static inline void update_cfs_group(struct sched_entity *se)
}
#endif /* CONFIG_FAIR_GROUP_SCHED */
-static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
-{
- struct rq *rq = rq_of(cfs_rq);
-
- if (&rq->cfs == cfs_rq) {
- /*
- * There are a few boundary cases this might miss but it should
- * get called often enough that that should (hopefully) not be
- * a real problem.
- *
- * It will not get called when we go idle, because the idle
- * thread is a different class (!fair), nor will the utilization
- * number include things like RT tasks.
- *
- * As is, the util number is not freq-invariant (we'd have to
- * implement arch_scale_freq_capacity() for that).
- *
- * See cpu_util_cfs().
- */
- cpufreq_update_util(rq, flags);
- }
-}
-#ifdef CONFIG_SMP
-static inline bool load_avg_is_decayed(struct sched_avg *sa)
+static void
+enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
- if (sa->load_sum)
- return false;
+ bool curr = cfs_rq->curr == se;
- if (sa->util_sum)
- return false;
+ /*
+ * If we're the current task, we must renormalise before calling
+ * update_curr().
+ */
+ if (curr)
+ place_entity(cfs_rq, se, flags);
- if (sa->runnable_sum)
- return false;
+ update_curr(cfs_rq);
/*
- * _avg must be null when _sum are null because _avg = _sum / divider
- * Make sure that rounding and/or propagation of PELT values never
- * break this.
+ * When enqueuing a sched_entity, we must:
+ * - Update loads to have both entity and cfs_rq synced with now.
+ * - For group_entity, update its runnable_weight to reflect the new
+ * h_nr_running of its group cfs_rq.
+ * - For group_entity, update its weight to reflect the new share of
+ * its group cfs_rq
+ * - Add its new weight to cfs_rq->load.weight
+ */
+ update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
+ se_update_runnable(se);
+ /*
+ * XXX update_load_avg() above will have attached us to the pelt sum;
+ * but update_cfs_group() here will re-adjust the weight and have to
+ * undo/redo all that. Seems wasteful.
*/
- SCHED_WARN_ON(sa->load_avg ||
- sa->util_avg ||
- sa->runnable_avg);
+ update_cfs_group(se);
- return true;
-}
+ /*
+ * XXX now that the entity has been re-weighted, and it's lag adjusted,
+ * we can place the entity.
+ */
+ if (!curr)
+ place_entity(cfs_rq, se, flags);
-static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
-{
- return u64_u32_load_copy(cfs_rq->avg.last_update_time,
- cfs_rq->last_update_time_copy);
-}
-#ifdef CONFIG_FAIR_GROUP_SCHED
-/*
- * Because list_add_leaf_cfs_rq always places a child cfs_rq on the list
- * immediately before a parent cfs_rq, and cfs_rqs are removed from the list
- * bottom-up, we only have to test whether the cfs_rq before us on the list
- * is our child.
- * If cfs_rq is not on the list, test whether a child needs its to be added to
- * connect a branch to the tree * (see list_add_leaf_cfs_rq() for details).
- */
-static inline bool child_cfs_rq_on_list(struct cfs_rq *cfs_rq)
-{
- struct cfs_rq *prev_cfs_rq;
- struct list_head *prev;
+ account_entity_enqueue(cfs_rq, se);
- if (cfs_rq->on_list) {
- prev = cfs_rq->leaf_cfs_rq_list.prev;
- } else {
- struct rq *rq = rq_of(cfs_rq);
+ /* Entity has migrated, no longer consider this task hot */
+ if (flags & ENQUEUE_MIGRATED)
+ se->exec_start = 0;
- prev = rq->tmp_alone_branch;
- }
+ check_schedstat_required();
+ update_stats_enqueue_fair(cfs_rq, se, flags);
+ if (!curr)
+ __enqueue_entity(cfs_rq, se);
+ se->on_rq = 1;
- prev_cfs_rq = container_of(prev, struct cfs_rq, leaf_cfs_rq_list);
+ if (cfs_rq->nr_running == 1) {
+ check_enqueue_throttle(cfs_rq);
+ if (!throttled_hierarchy(cfs_rq)) {
+ list_add_leaf_cfs_rq(cfs_rq);
+ } else {
+#ifdef CONFIG_CFS_BANDWIDTH
+ struct rq *rq = rq_of(cfs_rq);
- return (prev_cfs_rq->tg->parent == cfs_rq->tg);
+ if (cfs_rq_throttled(cfs_rq) && !cfs_rq->throttled_clock)
+ cfs_rq->throttled_clock = rq_clock(rq);
+ if (!cfs_rq->throttled_clock_self)
+ cfs_rq->throttled_clock_self = rq_clock(rq);
+#endif
+ }
+ }
}
-static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
+static void __clear_buddies_next(struct sched_entity *se)
{
- if (cfs_rq->load.weight)
- return false;
-
- if (!load_avg_is_decayed(&cfs_rq->avg))
- return false;
-
- if (child_cfs_rq_on_list(cfs_rq))
- return false;
+ for_each_sched_entity(se) {
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ if (cfs_rq->next != se)
+ break;
- return true;
+ cfs_rq->next = NULL;
+ }
}
-/**
- * update_tg_load_avg - update the tg's load avg
- * @cfs_rq: the cfs_rq whose avg changed
- *
- * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
- * However, because tg->load_avg is a global value there are performance
- * considerations.
- *
- * In order to avoid having to look at the other cfs_rq's, we use a
- * differential update where we store the last value we propagated. This in
- * turn allows skipping updates if the differential is 'small'.
- *
- * Updating tg's load_avg is necessary before update_cfs_share().
- */
-static inline void update_tg_load_avg(struct cfs_rq *cfs_rq)
+static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
- long delta;
- u64 now;
+ if (cfs_rq->next == se)
+ __clear_buddies_next(se);
+}
- /*
- * No need to update load_avg for root_task_group as it is not used.
- */
- if (cfs_rq->tg == &root_task_group)
- return;
+static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
- /* rq has been offline and doesn't contribute to the share anymore: */
- if (!cpu_active(cpu_of(rq_of(cfs_rq))))
- return;
+static void
+dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
+{
+ int action = UPDATE_TG;
+
+ if (entity_is_task(se) && task_on_rq_migrating(task_of(se)))
+ action |= DO_DETACH;
/*
- * For migration heavy workloads, access to tg->load_avg can be
- * unbound. Limit the update rate to at most once per ms.
+ * Update run-time statistics of the 'current'.
*/
- now = sched_clock_cpu(cpu_of(rq_of(cfs_rq)));
- if (now - cfs_rq->last_update_tg_load_avg < NSEC_PER_MSEC)
- return;
-
- delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
- if (abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
- atomic_long_add(delta, &cfs_rq->tg->load_avg);
- cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
- cfs_rq->last_update_tg_load_avg = now;
- }
-}
-
-static inline void clear_tg_load_avg(struct cfs_rq *cfs_rq)
-{
- long delta;
- u64 now;
+ update_curr(cfs_rq);
/*
- * No need to update load_avg for root_task_group, as it is not used.
+ * When dequeuing a sched_entity, we must:
+ * - Update loads to have both entity and cfs_rq synced with now.
+ * - For group_entity, update its runnable_weight to reflect the new
+ * h_nr_running of its group cfs_rq.
+ * - Subtract its previous weight from cfs_rq->load.weight.
+ * - For group entity, update its weight to reflect the new share
+ * of its group cfs_rq.
*/
- if (cfs_rq->tg == &root_task_group)
- return;
+ update_load_avg(cfs_rq, se, action);
+ se_update_runnable(se);
- now = sched_clock_cpu(cpu_of(rq_of(cfs_rq)));
- delta = 0 - cfs_rq->tg_load_avg_contrib;
- atomic_long_add(delta, &cfs_rq->tg->load_avg);
- cfs_rq->tg_load_avg_contrib = 0;
- cfs_rq->last_update_tg_load_avg = now;
-}
+ update_stats_dequeue_fair(cfs_rq, se, flags);
-/* CPU offline callback: */
-static void __maybe_unused clear_tg_offline_cfs_rqs(struct rq *rq)
-{
- struct task_group *tg;
+ clear_buddies(cfs_rq, se);
- lockdep_assert_rq_held(rq);
+ update_entity_lag(cfs_rq, se);
+ if (se != cfs_rq->curr)
+ __dequeue_entity(cfs_rq, se);
+ se->on_rq = 0;
+ account_entity_dequeue(cfs_rq, se);
- /*
- * The rq clock has already been updated in
- * set_rq_offline(), so we should skip updating
- * the rq clock again in unthrottle_cfs_rq().
- */
- rq_clock_start_loop_update(rq);
+ /* return excess runtime on last dequeue */
+ return_cfs_rq_runtime(cfs_rq);
- rcu_read_lock();
- list_for_each_entry_rcu(tg, &task_groups, list) {
- struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
+ update_cfs_group(se);
- clear_tg_load_avg(cfs_rq);
- }
- rcu_read_unlock();
+ /*
+ * Now advance min_vruntime if @se was the entity holding it back,
+ * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
+ * put back on, and if we advance min_vruntime, we'll be placed back
+ * further than we started -- i.e. we'll be penalized.
+ */
+ if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
+ update_min_vruntime(cfs_rq);
- rq_clock_stop_loop_update(rq);
+ if (cfs_rq->nr_running == 0)
+ update_idle_cfs_rq_clock_pelt(cfs_rq);
}
-/*
- * Called within set_task_rq() right before setting a task's CPU. The
- * caller only guarantees p->pi_lock is held; no other assumptions,
- * including the state of rq->lock, should be made.
- */
-void set_task_rq_fair(struct sched_entity *se,
- struct cfs_rq *prev, struct cfs_rq *next)
+static void
+set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
- u64 p_last_update_time;
- u64 n_last_update_time;
+ clear_buddies(cfs_rq, se);
- if (!sched_feat(ATTACH_AGE_LOAD))
- return;
+ /* 'current' is not kept within the tree. */
+ if (se->on_rq) {
+ /*
+ * Any task has to be enqueued before it get to execute on
+ * a CPU. So account for the time it spent waiting on the
+ * runqueue.
+ */
+ update_stats_wait_end_fair(cfs_rq, se);
+ __dequeue_entity(cfs_rq, se);
+ update_load_avg(cfs_rq, se, UPDATE_TG);
+ /*
+ * HACK, stash a copy of deadline at the point of pick in vlag,
+ * which isn't used until dequeue.
+ */
+ se->vlag = se->deadline;
+ }
+
+ update_stats_curr_start(cfs_rq, se);
+ cfs_rq->curr = se;
/*
- * We are supposed to update the task to "current" time, then its up to
- * date and ready to go to new CPU/cfs_rq. But we have difficulty in
- * getting what current time is, so simply throw away the out-of-date
- * time. This will result in the wakee task is less decayed, but giving
- * the wakee more load sounds not bad.
+ * Track our maximum slice length, if the CPU's load is at
+ * least twice that of our own weight (i.e. don't track it
+ * when there are only lesser-weight tasks around):
*/
- if (!(se->avg.last_update_time && prev))
- return;
+ if (schedstat_enabled() &&
+ rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
+ struct sched_statistics *stats;
- p_last_update_time = cfs_rq_last_update_time(prev);
- n_last_update_time = cfs_rq_last_update_time(next);
+ stats = __schedstats_from_se(se);
+ __schedstat_set(stats->slice_max,
+ max((u64)stats->slice_max,
+ se->sum_exec_runtime - se->prev_sum_exec_runtime));
+ }
- __update_load_avg_blocked_se(p_last_update_time, se);
- se->avg.last_update_time = n_last_update_time;
+ se->prev_sum_exec_runtime = se->sum_exec_runtime;
}
/*
- * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
- * propagate its contribution. The key to this propagation is the invariant
- * that for each group:
- *
- * ge->avg == grq->avg (1)
- *
- * _IFF_ we look at the pure running and runnable sums. Because they
- * represent the very same entity, just at different points in the hierarchy.
- *
- * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
- * and simply copies the running/runnable sum over (but still wrong, because
- * the group entity and group rq do not have their PELT windows aligned).
- *
- * However, update_tg_cfs_load() is more complex. So we have:
- *
- * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
- *
- * And since, like util, the runnable part should be directly transferable,
- * the following would _appear_ to be the straight forward approach:
- *
- * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
- *
- * And per (1) we have:
- *
- * ge->avg.runnable_avg == grq->avg.runnable_avg
- *
- * Which gives:
- *
- * ge->load.weight * grq->avg.load_avg
- * ge->avg.load_avg = ----------------------------------- (4)
- * grq->load.weight
- *
- * Except that is wrong!
- *
- * Because while for entities historical weight is not important and we
- * really only care about our future and therefore can consider a pure
- * runnable sum, runqueues can NOT do this.
- *
- * We specifically want runqueues to have a load_avg that includes
- * historical weights. Those represent the blocked load, the load we expect
- * to (shortly) return to us. This only works by keeping the weights as
- * integral part of the sum. We therefore cannot decompose as per (3).
- *
- * Another reason this doesn't work is that runnable isn't a 0-sum entity.
- * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
- * rq itself is runnable anywhere between 2/3 and 1 depending on how the
- * runnable section of these tasks overlap (or not). If they were to perfectly
- * align the rq as a whole would be runnable 2/3 of the time. If however we
- * always have at least 1 runnable task, the rq as a whole is always runnable.
- *
- * So we'll have to approximate.. :/
- *
- * Given the constraint:
- *
- * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
- *
- * We can construct a rule that adds runnable to a rq by assuming minimal
- * overlap.
- *
- * On removal, we'll assume each task is equally runnable; which yields:
- *
- * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
- *
- * XXX: only do this for the part of runnable > running ?
- *
+ * Pick the next process, keeping these things in mind, in this order:
+ * 1) keep things fair between processes/task groups
+ * 2) pick the "next" process, since someone really wants that to run
+ * 3) pick the "last" process, for cache locality
+ * 4) do not run the "skip" process, if something else is available
*/
-static inline void
-update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
+static struct sched_entity *
+pick_next_entity(struct cfs_rq *cfs_rq)
{
- long delta_sum, delta_avg = gcfs_rq->avg.util_avg - se->avg.util_avg;
- u32 new_sum, divider;
-
- /* Nothing to update */
- if (!delta_avg)
- return;
-
/*
- * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
- * See ___update_load_avg() for details.
+ * Enabling NEXT_BUDDY will affect latency but not fairness.
*/
- divider = get_pelt_divider(&cfs_rq->avg);
-
-
- /* Set new sched_entity's utilization */
- se->avg.util_avg = gcfs_rq->avg.util_avg;
- new_sum = se->avg.util_avg * divider;
- delta_sum = (long)new_sum - (long)se->avg.util_sum;
- se->avg.util_sum = new_sum;
-
- /* Update parent cfs_rq utilization */
- add_positive(&cfs_rq->avg.util_avg, delta_avg);
- add_positive(&cfs_rq->avg.util_sum, delta_sum);
+ if (sched_feat(NEXT_BUDDY) &&
+ cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))
+ return cfs_rq->next;
- /* See update_cfs_rq_load_avg() */
- cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
- cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
+ return pick_eevdf(cfs_rq);
}
-static inline void
-update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
-{
- long delta_sum, delta_avg = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
- u32 new_sum, divider;
-
- /* Nothing to update */
- if (!delta_avg)
- return;
+static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
+static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
+{
/*
- * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
- * See ___update_load_avg() for details.
+ * If still on the runqueue then deactivate_task()
+ * was not called and update_curr() has to be done:
*/
- divider = get_pelt_divider(&cfs_rq->avg);
+ if (prev->on_rq)
+ update_curr(cfs_rq);
- /* Set new sched_entity's runnable */
- se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
- new_sum = se->avg.runnable_avg * divider;
- delta_sum = (long)new_sum - (long)se->avg.runnable_sum;
- se->avg.runnable_sum = new_sum;
+ /* throttle cfs_rqs exceeding runtime */
+ check_cfs_rq_runtime(cfs_rq);
- /* Update parent cfs_rq runnable */
- add_positive(&cfs_rq->avg.runnable_avg, delta_avg);
- add_positive(&cfs_rq->avg.runnable_sum, delta_sum);
- /* See update_cfs_rq_load_avg() */
- cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum,
- cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER);
+ if (prev->on_rq) {
+ update_stats_wait_start_fair(cfs_rq, prev);
+ /* Put 'current' back into the tree. */
+ __enqueue_entity(cfs_rq, prev);
+ /* in !on_rq case, update occurred at dequeue */
+ update_load_avg(cfs_rq, prev, 0);
+ }
+ cfs_rq->curr = NULL;
}
-static inline void
-update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
+static void
+entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
{
- long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
- unsigned long load_avg;
- u64 load_sum = 0;
- s64 delta_sum;
- u32 divider;
-
- if (!runnable_sum)
- return;
-
- gcfs_rq->prop_runnable_sum = 0;
-
/*
- * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
- * See ___update_load_avg() for details.
+ * Update run-time statistics of the 'current'.
*/
- divider = get_pelt_divider(&cfs_rq->avg);
+ update_curr(cfs_rq);
- if (runnable_sum >= 0) {
- /*
- * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
- * the CPU is saturated running == runnable.
- */
- runnable_sum += se->avg.load_sum;
- runnable_sum = min_t(long, runnable_sum, divider);
- } else {
- /*
- * Estimate the new unweighted runnable_sum of the gcfs_rq by
- * assuming all tasks are equally runnable.
- */
- if (scale_load_down(gcfs_rq->load.weight)) {
- load_sum = div_u64(gcfs_rq->avg.load_sum,
- scale_load_down(gcfs_rq->load.weight));
- }
+ /*
+ * Ensure that runnable average is periodically updated.
+ */
+ update_load_avg(cfs_rq, curr, UPDATE_TG);
+ update_cfs_group(curr);
- /* But make sure to not inflate se's runnable */
- runnable_sum = min(se->avg.load_sum, load_sum);
+#ifdef CONFIG_SCHED_HRTICK
+ /*
+ * queued ticks are scheduled to match the slice, so don't bother
+ * validating it and just reschedule.
+ */
+ if (queued) {
+ resched_curr(rq_of(cfs_rq));
+ return;
}
-
/*
- * runnable_sum can't be lower than running_sum
- * Rescale running sum to be in the same range as runnable sum
- * running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT]
- * runnable_sum is in [0 : LOAD_AVG_MAX]
+ * don't let the period tick interfere with the hrtick preemption
*/
- running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
- runnable_sum = max(runnable_sum, running_sum);
+ if (!sched_feat(DOUBLE_TICK) &&
+ hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
+ return;
+#endif
+}
- load_sum = se_weight(se) * runnable_sum;
- load_avg = div_u64(load_sum, divider);
- delta_avg = load_avg - se->avg.load_avg;
- if (!delta_avg)
- return;
+/**************************************************
+ * CFS bandwidth control machinery
+ */
- delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
+#ifdef CONFIG_CFS_BANDWIDTH
- se->avg.load_sum = runnable_sum;
- se->avg.load_avg = load_avg;
- add_positive(&cfs_rq->avg.load_avg, delta_avg);
- add_positive(&cfs_rq->avg.load_sum, delta_sum);
- /* See update_cfs_rq_load_avg() */
- cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum,
- cfs_rq->avg.load_avg * PELT_MIN_DIVIDER);
-}
+#ifdef CONFIG_JUMP_LABEL
+static struct static_key __cfs_bandwidth_used;
-static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
+static inline bool cfs_bandwidth_used(void)
{
- cfs_rq->propagate = 1;
- cfs_rq->prop_runnable_sum += runnable_sum;
+ return static_key_false(&__cfs_bandwidth_used);
}
-/* Update task and its cfs_rq load average */
-static inline int propagate_entity_load_avg(struct sched_entity *se)
+void cfs_bandwidth_usage_inc(void)
{
- struct cfs_rq *cfs_rq, *gcfs_rq;
-
- if (entity_is_task(se))
- return 0;
-
- gcfs_rq = group_cfs_rq(se);
- if (!gcfs_rq->propagate)
- return 0;
-
- gcfs_rq->propagate = 0;
-
- cfs_rq = cfs_rq_of(se);
+ static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
+}
- add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
+void cfs_bandwidth_usage_dec(void)
+{
+ static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
+}
+#else /* CONFIG_JUMP_LABEL */
+static bool cfs_bandwidth_used(void)
+{
+ return true;
+}
- update_tg_cfs_util(cfs_rq, se, gcfs_rq);
- update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
- update_tg_cfs_load(cfs_rq, se, gcfs_rq);
+void cfs_bandwidth_usage_inc(void) {}
+void cfs_bandwidth_usage_dec(void) {}
+#endif /* CONFIG_JUMP_LABEL */
- trace_pelt_cfs_tp(cfs_rq);
- trace_pelt_se_tp(se);
+/*
+ * default period for cfs group bandwidth.
+ * default: 0.1s, units: nanoseconds
+ */
+static inline u64 default_cfs_period(void)
+{
+ return 100000000ULL;
+}
- return 1;
+static inline u64 sched_cfs_bandwidth_slice(void)
+{
+ return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
}
/*
- * Check if we need to update the load and the utilization of a blocked
- * group_entity:
+ * Replenish runtime according to assigned quota. We use sched_clock_cpu
+ * directly instead of rq->clock to avoid adding additional synchronization
+ * around rq->lock.
+ *
+ * requires cfs_b->lock
*/
-static inline bool skip_blocked_update(struct sched_entity *se)
+void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
{
- struct cfs_rq *gcfs_rq = group_cfs_rq(se);
+ s64 runtime;
- /*
- * If sched_entity still have not zero load or utilization, we have to
- * decay it:
- */
- if (se->avg.load_avg || se->avg.util_avg)
- return false;
+ if (unlikely(cfs_b->quota == RUNTIME_INF))
+ return;
- /*
- * If there is a pending propagation, we have to update the load and
- * the utilization of the sched_entity:
- */
- if (gcfs_rq->propagate)
- return false;
+ cfs_b->runtime += cfs_b->quota;
+ runtime = cfs_b->runtime_snap - cfs_b->runtime;
+ if (runtime > 0) {
+ cfs_b->burst_time += runtime;
+ cfs_b->nr_burst++;
+ }
- /*
- * Otherwise, the load and the utilization of the sched_entity is
- * already zero and there is no pending propagation, so it will be a
- * waste of time to try to decay it:
- */
- return true;
+ cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);
+ cfs_b->runtime_snap = cfs_b->runtime;
}
-#else /* CONFIG_FAIR_GROUP_SCHED */
-
-static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) {}
-
-static inline void clear_tg_offline_cfs_rqs(struct rq *rq) {}
-
-static inline int propagate_entity_load_avg(struct sched_entity *se)
+static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
- return 0;
+ return &tg->cfs_bandwidth;
}
-static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
-
-#endif /* CONFIG_FAIR_GROUP_SCHED */
-
-#ifdef CONFIG_NO_HZ_COMMON
-static inline void migrate_se_pelt_lag(struct sched_entity *se)
+/* returns 0 on failure to allocate runtime */
+static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
+ struct cfs_rq *cfs_rq, u64 target_runtime)
{
- u64 throttled = 0, now, lut;
- struct cfs_rq *cfs_rq;
- struct rq *rq;
- bool is_idle;
-
- if (load_avg_is_decayed(&se->avg))
- return;
-
- cfs_rq = cfs_rq_of(se);
- rq = rq_of(cfs_rq);
+ u64 min_amount, amount = 0;
- rcu_read_lock();
- is_idle = is_idle_task(rcu_dereference(rq->curr));
- rcu_read_unlock();
+ lockdep_assert_held(&cfs_b->lock);
- /*
- * The lag estimation comes with a cost we don't want to pay all the
- * time. Hence, limiting to the case where the source CPU is idle and
- * we know we are at the greatest risk to have an outdated clock.
- */
- if (!is_idle)
- return;
+ /* note: this is a positive sum as runtime_remaining <= 0 */
+ min_amount = target_runtime - cfs_rq->runtime_remaining;
- /*
- * Estimated "now" is: last_update_time + cfs_idle_lag + rq_idle_lag, where:
- *
- * last_update_time (the cfs_rq's last_update_time)
- * = cfs_rq_clock_pelt()@cfs_rq_idle
- * = rq_clock_pelt()@cfs_rq_idle
- * - cfs->throttled_clock_pelt_time@..._rq_idle
- *
- * cfs_idle_lag (delta between rq's update and cfs_rq's update)
- * = rq_clock_pelt()@rq_idle - rq_clock_pelt()@cfs_rq_idle
- *
- * rq_idle_lag (delta between now and rq's update)
- * = sched_clock_cpu() - rq_clock()@rq_idle
- *
- * We can then write:
- *
- * now = rq_clock_pelt()@rq_idle - cfs->throttled_clock_pelt_time +
- * sched_clock_cpu() - rq_clock()@rq_idle
- * Where:
- * rq_clock_pelt()@rq_idle is rq->clock_pelt_idle
- * rq_clock()@rq_idle is rq->clock_idle
- * cfs->throttled_clock_pelt_time@..._rq_idle
- * is cfs_rq->throttled_pelt_idle
- */
+ if (cfs_b->quota == RUNTIME_INF)
+ amount = min_amount;
+ else {
+ start_cfs_bandwidth(cfs_b);
-#ifdef CONFIG_CFS_BANDWIDTH
- throttled = u64_u32_load(cfs_rq->throttled_pelt_idle);
- /* The clock has been stopped for throttling */
- if (throttled == U64_MAX)
- return;
-#endif
- now = u64_u32_load(rq->clock_pelt_idle);
- /*
- * Paired with _update_idle_rq_clock_pelt(). It ensures at the worst case
- * is observed the old clock_pelt_idle value and the new clock_idle,
- * which lead to an underestimation. The opposite would lead to an
- * overestimation.
- */
- smp_rmb();
- lut = cfs_rq_last_update_time(cfs_rq);
+ if (cfs_b->runtime > 0) {
+ amount = min(cfs_b->runtime, min_amount);
+ cfs_b->runtime -= amount;
+ cfs_b->idle = 0;
+ }
+ }
- now -= throttled;
- if (now < lut)
- /*
- * cfs_rq->avg.last_update_time is more recent than our
- * estimation, let's use it.
- */
- now = lut;
- else
- now += sched_clock_cpu(cpu_of(rq)) - u64_u32_load(rq->clock_idle);
+ cfs_rq->runtime_remaining += amount;
- __update_load_avg_blocked_se(now, se);
+ return cfs_rq->runtime_remaining > 0;
}
-#else
-static void migrate_se_pelt_lag(struct sched_entity *se) {}
-#endif
-
-/**
- * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
- * @now: current time, as per cfs_rq_clock_pelt()
- * @cfs_rq: cfs_rq to update
- *
- * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
- * avg. The immediate corollary is that all (fair) tasks must be attached.
- *
- * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
- *
- * Return: true if the load decayed or we removed load.
- *
- * Since both these conditions indicate a changed cfs_rq->avg.load we should
- * call update_tg_load_avg() when this function returns true.
- */
-static inline int
-update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
-{
- unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0;
- struct sched_avg *sa = &cfs_rq->avg;
- int decayed = 0;
-
- if (cfs_rq->removed.nr) {
- unsigned long r;
- u32 divider = get_pelt_divider(&cfs_rq->avg);
-
- raw_spin_lock(&cfs_rq->removed.lock);
- swap(cfs_rq->removed.util_avg, removed_util);
- swap(cfs_rq->removed.load_avg, removed_load);
- swap(cfs_rq->removed.runnable_avg, removed_runnable);
- cfs_rq->removed.nr = 0;
- raw_spin_unlock(&cfs_rq->removed.lock);
-
- r = removed_load;
- sub_positive(&sa->load_avg, r);
- sub_positive(&sa->load_sum, r * divider);
- /* See sa->util_sum below */
- sa->load_sum = max_t(u32, sa->load_sum, sa->load_avg * PELT_MIN_DIVIDER);
-
- r = removed_util;
- sub_positive(&sa->util_avg, r);
- sub_positive(&sa->util_sum, r * divider);
- /*
- * Because of rounding, se->util_sum might ends up being +1 more than
- * cfs->util_sum. Although this is not a problem by itself, detaching
- * a lot of tasks with the rounding problem between 2 updates of
- * util_avg (~1ms) can make cfs->util_sum becoming null whereas
- * cfs_util_avg is not.
- * Check that util_sum is still above its lower bound for the new
- * util_avg. Given that period_contrib might have moved since the last
- * sync, we are only sure that util_sum must be above or equal to
- * util_avg * minimum possible divider
- */
- sa->util_sum = max_t(u32, sa->util_sum, sa->util_avg * PELT_MIN_DIVIDER);
-
- r = removed_runnable;
- sub_positive(&sa->runnable_avg, r);
- sub_positive(&sa->runnable_sum, r * divider);
- /* See sa->util_sum above */
- sa->runnable_sum = max_t(u32, sa->runnable_sum,
- sa->runnable_avg * PELT_MIN_DIVIDER);
- /*
- * removed_runnable is the unweighted version of removed_load so we
- * can use it to estimate removed_load_sum.
- */
- add_tg_cfs_propagate(cfs_rq,
- -(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT);
+/* returns 0 on failure to allocate runtime */
+static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
+{
+ struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
+ int ret;
- decayed = 1;
- }
+ raw_spin_lock(&cfs_b->lock);
+ ret = __assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice());
+ raw_spin_unlock(&cfs_b->lock);
- decayed |= __update_load_avg_cfs_rq(now, cfs_rq);
- u64_u32_store_copy(sa->last_update_time,
- cfs_rq->last_update_time_copy,
- sa->last_update_time);
- return decayed;
+ return ret;
}
-/**
- * attach_entity_load_avg - attach this entity to its cfs_rq load avg
- * @cfs_rq: cfs_rq to attach to
- * @se: sched_entity to attach
- *
- * Must call update_cfs_rq_load_avg() before this, since we rely on
- * cfs_rq->avg.last_update_time being current.
- */
-static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
{
- /*
- * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
- * See ___update_load_avg() for details.
- */
- u32 divider = get_pelt_divider(&cfs_rq->avg);
+ /* dock delta_exec before expiring quota (as it could span periods) */
+ cfs_rq->runtime_remaining -= delta_exec;
- /*
- * When we attach the @se to the @cfs_rq, we must align the decay
- * window because without that, really weird and wonderful things can
- * happen.
- *
- * XXX illustrate
- */
- se->avg.last_update_time = cfs_rq->avg.last_update_time;
- se->avg.period_contrib = cfs_rq->avg.period_contrib;
+ if (likely(cfs_rq->runtime_remaining > 0))
+ return;
+ if (cfs_rq->throttled)
+ return;
/*
- * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
- * period_contrib. This isn't strictly correct, but since we're
- * entirely outside of the PELT hierarchy, nobody cares if we truncate
- * _sum a little.
+ * if we're unable to extend our runtime we resched so that the active
+ * hierarchy can be throttled
*/
- se->avg.util_sum = se->avg.util_avg * divider;
-
- se->avg.runnable_sum = se->avg.runnable_avg * divider;
-
- se->avg.load_sum = se->avg.load_avg * divider;
- if (se_weight(se) < se->avg.load_sum)
- se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se));
- else
- se->avg.load_sum = 1;
-
- enqueue_load_avg(cfs_rq, se);
- cfs_rq->avg.util_avg += se->avg.util_avg;
- cfs_rq->avg.util_sum += se->avg.util_sum;
- cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
- cfs_rq->avg.runnable_sum += se->avg.runnable_sum;
-
- add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
-
- cfs_rq_util_change(cfs_rq, 0);
-
- trace_pelt_cfs_tp(cfs_rq);
+ if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
+ resched_curr(rq_of(cfs_rq));
}
-/**
- * detach_entity_load_avg - detach this entity from its cfs_rq load avg
- * @cfs_rq: cfs_rq to detach from
- * @se: sched_entity to detach
- *
- * Must call update_cfs_rq_load_avg() before this, since we rely on
- * cfs_rq->avg.last_update_time being current.
- */
-static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+static __always_inline
+void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
{
- dequeue_load_avg(cfs_rq, se);
- sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
- sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
- /* See update_cfs_rq_load_avg() */
- cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
- cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
-
- sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
- sub_positive(&cfs_rq->avg.runnable_sum, se->avg.runnable_sum);
- /* See update_cfs_rq_load_avg() */
- cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum,
- cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER);
-
- add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
-
- cfs_rq_util_change(cfs_rq, 0);
+ if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
+ return;
- trace_pelt_cfs_tp(cfs_rq);
+ __account_cfs_rq_runtime(cfs_rq, delta_exec);
}
-/*
- * Optional action to be done while updating the load average
- */
-#define UPDATE_TG 0x1
-#define SKIP_AGE_LOAD 0x2
-#define DO_ATTACH 0x4
-#define DO_DETACH 0x8
-
-/* Update task and its cfs_rq load average */
-static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
+static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
- u64 now = cfs_rq_clock_pelt(cfs_rq);
- int decayed;
-
- /*
- * Track task load average for carrying it to new CPU after migrated, and
- * track group sched_entity load average for task_h_load calculation in migration
- */
- if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
- __update_load_avg_se(now, cfs_rq, se);
-
- decayed = update_cfs_rq_load_avg(now, cfs_rq);
- decayed |= propagate_entity_load_avg(se);
-
- if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
-
- /*
- * DO_ATTACH means we're here from enqueue_entity().
- * !last_update_time means we've passed through
- * migrate_task_rq_fair() indicating we migrated.
- *
- * IOW we're enqueueing a task on a new CPU.
- */
- attach_entity_load_avg(cfs_rq, se);
- update_tg_load_avg(cfs_rq);
-
- } else if (flags & DO_DETACH) {
- /*
- * DO_DETACH means we're here from dequeue_entity()
- * and we are migrating task out of the CPU.
- */
- detach_entity_load_avg(cfs_rq, se);
- update_tg_load_avg(cfs_rq);
- } else if (decayed) {
- cfs_rq_util_change(cfs_rq, 0);
-
- if (flags & UPDATE_TG)
- update_tg_load_avg(cfs_rq);
- }
+ return cfs_bandwidth_used() && cfs_rq->throttled;
}
-/*
- * Synchronize entity load avg of dequeued entity without locking
- * the previous rq.
- */
-static void sync_entity_load_avg(struct sched_entity *se)
+/* check whether cfs_rq, or any parent, is throttled */
+static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
- struct cfs_rq *cfs_rq = cfs_rq_of(se);
- u64 last_update_time;
-
- last_update_time = cfs_rq_last_update_time(cfs_rq);
- __update_load_avg_blocked_se(last_update_time, se);
+ return cfs_bandwidth_used() && cfs_rq->throttle_count;
}
/*
- * Task first catches up with cfs_rq, and then subtract
- * itself from the cfs_rq (task must be off the queue now).
+ * Ensure that neither of the group entities corresponding to src_cpu or
+ * dest_cpu are members of a throttled hierarchy when performing group
+ * load-balance operations.
*/
-static void remove_entity_load_avg(struct sched_entity *se)
+int throttled_lb_pair(struct task_group *tg, int src_cpu, int dest_cpu)
{
- struct cfs_rq *cfs_rq = cfs_rq_of(se);
- unsigned long flags;
-
- /*
- * tasks cannot exit without having gone through wake_up_new_task() ->
- * enqueue_task_fair() which will have added things to the cfs_rq,
- * so we can remove unconditionally.
- */
+ struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
- sync_entity_load_avg(se);
+ src_cfs_rq = tg->cfs_rq[src_cpu];
+ dest_cfs_rq = tg->cfs_rq[dest_cpu];
- raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
- ++cfs_rq->removed.nr;
- cfs_rq->removed.util_avg += se->avg.util_avg;
- cfs_rq->removed.load_avg += se->avg.load_avg;
- cfs_rq->removed.runnable_avg += se->avg.runnable_avg;
- raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
+ return throttled_hierarchy(src_cfs_rq) ||
+ throttled_hierarchy(dest_cfs_rq);
}
-static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
+static int tg_unthrottle_up(struct task_group *tg, void *data)
{
- return cfs_rq->avg.runnable_avg;
-}
+ struct rq *rq = data;
+ struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
-static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
-{
- return cfs_rq->avg.load_avg;
-}
+ cfs_rq->throttle_count--;
+ if (!cfs_rq->throttle_count) {
+ cfs_rq->throttled_clock_pelt_time += rq_clock_pelt(rq) -
+ cfs_rq->throttled_clock_pelt;
-static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf);
+ /* Add cfs_rq with load or one or more already running entities to the list */
+ if (!cfs_rq_is_decayed(cfs_rq))
+ list_add_leaf_cfs_rq(cfs_rq);
-static inline unsigned long task_util(struct task_struct *p)
-{
- return READ_ONCE(p->se.avg.util_avg);
-}
+ if (cfs_rq->throttled_clock_self) {
+ u64 delta = rq_clock(rq) - cfs_rq->throttled_clock_self;
-static inline unsigned long task_runnable(struct task_struct *p)
-{
- return READ_ONCE(p->se.avg.runnable_avg);
-}
+ cfs_rq->throttled_clock_self = 0;
-static inline unsigned long _task_util_est(struct task_struct *p)
-{
- return READ_ONCE(p->se.avg.util_est) & ~UTIL_AVG_UNCHANGED;
-}
+ if (SCHED_WARN_ON((s64)delta < 0))
+ delta = 0;
-static inline unsigned long task_util_est(struct task_struct *p)
-{
- return max(task_util(p), _task_util_est(p));
+ cfs_rq->throttled_clock_self_time += delta;
+ }
+ }
+
+ return 0;
}
-static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
- struct task_struct *p)
+static int tg_throttle_down(struct task_group *tg, void *data)
{
- unsigned int enqueued;
+ struct rq *rq = data;
+ struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
- if (!sched_feat(UTIL_EST))
- return;
+ /* group is entering throttled state, stop time */
+ if (!cfs_rq->throttle_count) {
+ cfs_rq->throttled_clock_pelt = rq_clock_pelt(rq);
+ list_del_leaf_cfs_rq(cfs_rq);
- /* Update root cfs_rq's estimated utilization */
- enqueued = cfs_rq->avg.util_est;
- enqueued += _task_util_est(p);
- WRITE_ONCE(cfs_rq->avg.util_est, enqueued);
+ SCHED_WARN_ON(cfs_rq->throttled_clock_self);
+ if (cfs_rq->nr_running)
+ cfs_rq->throttled_clock_self = rq_clock(rq);
+ }
+ cfs_rq->throttle_count++;
- trace_sched_util_est_cfs_tp(cfs_rq);
+ return 0;
}
-static inline void util_est_dequeue(struct cfs_rq *cfs_rq,
- struct task_struct *p)
+static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
{
- unsigned int enqueued;
+ struct rq *rq = rq_of(cfs_rq);
+ struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
+ struct sched_entity *se;
+ long task_delta, idle_task_delta, dequeue = 1;
- if (!sched_feat(UTIL_EST))
- return;
+ raw_spin_lock(&cfs_b->lock);
+ /* This will start the period timer if necessary */
+ if (__assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) {
+ /*
+ * We have raced with bandwidth becoming available, and if we
+ * actually throttled the timer might not unthrottle us for an
+ * entire period. We additionally needed to make sure that any
+ * subsequent check_cfs_rq_runtime calls agree not to throttle
+ * us, as we may commit to do cfs put_prev+pick_next, so we ask
+ * for 1ns of runtime rather than just check cfs_b.
+ */
+ dequeue = 0;
+ } else {
+ list_add_tail_rcu(&cfs_rq->throttled_list,
+ &cfs_b->throttled_cfs_rq);
+ }
+ raw_spin_unlock(&cfs_b->lock);
- /* Update root cfs_rq's estimated utilization */
- enqueued = cfs_rq->avg.util_est;
- enqueued -= min_t(unsigned int, enqueued, _task_util_est(p));
- WRITE_ONCE(cfs_rq->avg.util_est, enqueued);
+ if (!dequeue)
+ return false; /* Throttle no longer required. */
- trace_sched_util_est_cfs_tp(cfs_rq);
-}
+ se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
-#define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100)
+ /* freeze hierarchy runnable averages while throttled */
+ rcu_read_lock();
+ walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
+ rcu_read_unlock();
-static inline void util_est_update(struct cfs_rq *cfs_rq,
- struct task_struct *p,
- bool task_sleep)
-{
- unsigned int ewma, dequeued, last_ewma_diff;
+ task_delta = cfs_rq->h_nr_running;
+ idle_task_delta = cfs_rq->idle_h_nr_running;
+ for_each_sched_entity(se) {
+ struct cfs_rq *qcfs_rq = cfs_rq_of(se);
+ /* throttled entity or throttle-on-deactivate */
+ if (!se->on_rq)
+ goto done;
- if (!sched_feat(UTIL_EST))
- return;
+ dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
- /*
- * Skip update of task's estimated utilization when the task has not
- * yet completed an activation, e.g. being migrated.
- */
- if (!task_sleep)
- return;
+ if (cfs_rq_is_idle(group_cfs_rq(se)))
+ idle_task_delta = cfs_rq->h_nr_running;
- /* Get current estimate of utilization */
- ewma = READ_ONCE(p->se.avg.util_est);
+ qcfs_rq->h_nr_running -= task_delta;
+ qcfs_rq->idle_h_nr_running -= idle_task_delta;
- /*
- * If the PELT values haven't changed since enqueue time,
- * skip the util_est update.
- */
- if (ewma & UTIL_AVG_UNCHANGED)
- return;
+ if (qcfs_rq->load.weight) {
+ /* Avoid re-evaluating load for this entity: */
+ se = parent_entity(se);
+ break;
+ }
+ }
- /* Get utilization at dequeue */
- dequeued = task_util(p);
+ for_each_sched_entity(se) {
+ struct cfs_rq *qcfs_rq = cfs_rq_of(se);
+ /* throttled entity or throttle-on-deactivate */
+ if (!se->on_rq)
+ goto done;
- /*
- * Reset EWMA on utilization increases, the moving average is used only
- * to smooth utilization decreases.
- */
- if (ewma <= dequeued) {
- ewma = dequeued;
- goto done;
+ update_load_avg(qcfs_rq, se, 0);
+ se_update_runnable(se);
+
+ if (cfs_rq_is_idle(group_cfs_rq(se)))
+ idle_task_delta = cfs_rq->h_nr_running;
+
+ qcfs_rq->h_nr_running -= task_delta;
+ qcfs_rq->idle_h_nr_running -= idle_task_delta;
}
- /*
- * Skip update of task's estimated utilization when its members are
- * already ~1% close to its last activation value.
- */
- last_ewma_diff = ewma - dequeued;
- if (last_ewma_diff < UTIL_EST_MARGIN)
- goto done;
+ /* At this point se is NULL and we are at root level*/
+ sub_nr_running(rq, task_delta);
+done:
/*
- * To avoid overestimation of actual task utilization, skip updates if
- * we cannot grant there is idle time in this CPU.
+ * Note: distribution will already see us throttled via the
+ * throttled-list. rq->lock protects completion.
*/
- if (dequeued > arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq))))
- return;
+ cfs_rq->throttled = 1;
+ SCHED_WARN_ON(cfs_rq->throttled_clock);
+ if (cfs_rq->nr_running)
+ cfs_rq->throttled_clock = rq_clock(rq);
+ return true;
+}
- /*
- * To avoid underestimate of task utilization, skip updates of EWMA if
- * we cannot grant that thread got all CPU time it wanted.
- */
- if ((dequeued + UTIL_EST_MARGIN) < task_runnable(p))
- goto done;
+void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
+{
+ struct rq *rq = rq_of(cfs_rq);
+ struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
+ struct sched_entity *se;
+ long task_delta, idle_task_delta;
+ se = cfs_rq->tg->se[cpu_of(rq)];
- /*
- * Update Task's estimated utilization
- *
- * When *p completes an activation we can consolidate another sample
- * of the task size. This is done by using this value to update the
- * Exponential Weighted Moving Average (EWMA):
- *
- * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
- * = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
- * = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
- * = w * ( -last_ewma_diff ) + ewma(t-1)
- * = w * (-last_ewma_diff + ewma(t-1) / w)
- *
- * Where 'w' is the weight of new samples, which is configured to be
- * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
- */
- ewma <<= UTIL_EST_WEIGHT_SHIFT;
- ewma -= last_ewma_diff;
- ewma >>= UTIL_EST_WEIGHT_SHIFT;
-done:
- ewma |= UTIL_AVG_UNCHANGED;
- WRITE_ONCE(p->se.avg.util_est, ewma);
+ cfs_rq->throttled = 0;
- trace_sched_util_est_se_tp(&p->se);
-}
+ update_rq_clock(rq);
-static inline int util_fits_cpu(unsigned long util,
- unsigned long uclamp_min,
- unsigned long uclamp_max,
- int cpu)
-{
- unsigned long capacity_orig, capacity_orig_thermal;
- unsigned long capacity = capacity_of(cpu);
- bool fits, uclamp_max_fits;
+ raw_spin_lock(&cfs_b->lock);
+ if (cfs_rq->throttled_clock) {
+ cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
+ cfs_rq->throttled_clock = 0;
+ }
+ list_del_rcu(&cfs_rq->throttled_list);
+ raw_spin_unlock(&cfs_b->lock);
- /*
- * Check if the real util fits without any uclamp boost/cap applied.
- */
- fits = fits_capacity(util, capacity);
+ /* update hierarchical throttle state */
+ walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
- if (!uclamp_is_used())
- return fits;
+ if (!cfs_rq->load.weight) {
+ if (!cfs_rq->on_list)
+ return;
+ /*
+ * Nothing to run but something to decay (on_list)?
+ * Complete the branch.
+ */
+ for_each_sched_entity(se) {
+ if (list_add_leaf_cfs_rq(cfs_rq_of(se)))
+ break;
+ }
+ goto unthrottle_throttle;
+ }
- /*
- * We must use arch_scale_cpu_capacity() for comparing against uclamp_min and
- * uclamp_max. We only care about capacity pressure (by using
- * capacity_of()) for comparing against the real util.
- *
- * If a task is boosted to 1024 for example, we don't want a tiny
- * pressure to skew the check whether it fits a CPU or not.
- *
- * Similarly if a task is capped to arch_scale_cpu_capacity(little_cpu), it
- * should fit a little cpu even if there's some pressure.
- *
- * Only exception is for thermal pressure since it has a direct impact
- * on available OPP of the system.
- *
- * We honour it for uclamp_min only as a drop in performance level
- * could result in not getting the requested minimum performance level.
- *
- * For uclamp_max, we can tolerate a drop in performance level as the
- * goal is to cap the task. So it's okay if it's getting less.
- */
- capacity_orig = arch_scale_cpu_capacity(cpu);
- capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
+ task_delta = cfs_rq->h_nr_running;
+ idle_task_delta = cfs_rq->idle_h_nr_running;
+ for_each_sched_entity(se) {
+ struct cfs_rq *qcfs_rq = cfs_rq_of(se);
- /*
- * We want to force a task to fit a cpu as implied by uclamp_max.
- * But we do have some corner cases to cater for..
- *
- *
- * C=z
- * | ___
- * | C=y | |
- * |_ _ _ _ _ _ _ _ _ ___ _ _ _ | _ | _ _ _ _ _ uclamp_max
- * | C=x | | | |
- * | ___ | | | |
- * | | | | | | | (util somewhere in this region)
- * | | | | | | |
- * | | | | | | |
- * +----------------------------------------
- * CPU0 CPU1 CPU2
- *
- * In the above example if a task is capped to a specific performance
- * point, y, then when:
- *
- * * util = 80% of x then it does not fit on CPU0 and should migrate
- * to CPU1
- * * util = 80% of y then it is forced to fit on CPU1 to honour
- * uclamp_max request.
- *
- * which is what we're enforcing here. A task always fits if
- * uclamp_max <= capacity_orig. But when uclamp_max > capacity_orig,
- * the normal upmigration rules should withhold still.
- *
- * Only exception is when we are on max capacity, then we need to be
- * careful not to block overutilized state. This is so because:
- *
- * 1. There's no concept of capping at max_capacity! We can't go
- * beyond this performance level anyway.
- * 2. The system is being saturated when we're operating near
- * max capacity, it doesn't make sense to block overutilized.
- */
- uclamp_max_fits = (capacity_orig == SCHED_CAPACITY_SCALE) && (uclamp_max == SCHED_CAPACITY_SCALE);
- uclamp_max_fits = !uclamp_max_fits && (uclamp_max <= capacity_orig);
- fits = fits || uclamp_max_fits;
+ if (se->on_rq)
+ break;
+ enqueue_entity(qcfs_rq, se, ENQUEUE_WAKEUP);
- /*
- *
- * C=z
- * | ___ (region a, capped, util >= uclamp_max)
- * | C=y | |
- * |_ _ _ _ _ _ _ _ _ ___ _ _ _ | _ | _ _ _ _ _ uclamp_max
- * | C=x | | | |
- * | ___ | | | | (region b, uclamp_min <= util <= uclamp_max)
- * |_ _ _|_ _|_ _ _ _| _ | _ _ _| _ | _ _ _ _ _ uclamp_min
- * | | | | | | |
- * | | | | | | | (region c, boosted, util < uclamp_min)
- * +----------------------------------------
- * CPU0 CPU1 CPU2
- *
- * a) If util > uclamp_max, then we're capped, we don't care about
- * actual fitness value here. We only care if uclamp_max fits
- * capacity without taking margin/pressure into account.
- * See comment above.
- *
- * b) If uclamp_min <= util <= uclamp_max, then the normal
- * fits_capacity() rules apply. Except we need to ensure that we
- * enforce we remain within uclamp_max, see comment above.
- *
- * c) If util < uclamp_min, then we are boosted. Same as (b) but we
- * need to take into account the boosted value fits the CPU without
- * taking margin/pressure into account.
- *
- * Cases (a) and (b) are handled in the 'fits' variable already. We
- * just need to consider an extra check for case (c) after ensuring we
- * handle the case uclamp_min > uclamp_max.
- */
- uclamp_min = min(uclamp_min, uclamp_max);
- if (fits && (util < uclamp_min) && (uclamp_min > capacity_orig_thermal))
- return -1;
+ if (cfs_rq_is_idle(group_cfs_rq(se)))
+ idle_task_delta = cfs_rq->h_nr_running;
- return fits;
-}
+ qcfs_rq->h_nr_running += task_delta;
+ qcfs_rq->idle_h_nr_running += idle_task_delta;
-static inline int task_fits_cpu(struct task_struct *p, int cpu)
-{
- unsigned long uclamp_min = uclamp_eff_value(p, UCLAMP_MIN);
- unsigned long uclamp_max = uclamp_eff_value(p, UCLAMP_MAX);
- unsigned long util = task_util_est(p);
- /*
- * Return true only if the cpu fully fits the task requirements, which
- * include the utilization but also the performance hints.
- */
- return (util_fits_cpu(util, uclamp_min, uclamp_max, cpu) > 0);
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(qcfs_rq))
+ goto unthrottle_throttle;
+ }
+
+ for_each_sched_entity(se) {
+ struct cfs_rq *qcfs_rq = cfs_rq_of(se);
+
+ update_load_avg(qcfs_rq, se, UPDATE_TG);
+ se_update_runnable(se);
+
+ if (cfs_rq_is_idle(group_cfs_rq(se)))
+ idle_task_delta = cfs_rq->h_nr_running;
+
+ qcfs_rq->h_nr_running += task_delta;
+ qcfs_rq->idle_h_nr_running += idle_task_delta;
+
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(qcfs_rq))
+ goto unthrottle_throttle;
+ }
+
+ /* At this point se is NULL and we are at root level*/
+ add_nr_running(rq, task_delta);
+
+unthrottle_throttle:
+ assert_list_leaf_cfs_rq(rq);
+
+ /* Determine whether we need to wake up potentially idle CPU: */
+ if (rq->curr == rq->idle && rq->cfs.nr_running)
+ resched_curr(rq);
}
-static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
+#ifdef CONFIG_SMP
+static void __cfsb_csd_unthrottle(void *arg)
{
- int cpu = cpu_of(rq);
+ struct cfs_rq *cursor, *tmp;
+ struct rq *rq = arg;
+ struct rq_flags rf;
- if (!sched_asym_cpucap_active())
- return;
+ rq_lock(rq, &rf);
/*
- * Affinity allows us to go somewhere higher? Or are we on biggest
- * available CPU already? Or do we fit into this CPU ?
+ * Iterating over the list can trigger several call to
+ * update_rq_clock() in unthrottle_cfs_rq().
+ * Do it once and skip the potential next ones.
*/
- if (!p || (p->nr_cpus_allowed == 1) ||
- (arch_scale_cpu_capacity(cpu) == p->max_allowed_capacity) ||
- task_fits_cpu(p, cpu)) {
-
- rq->misfit_task_load = 0;
- return;
- }
+ update_rq_clock(rq);
+ rq_clock_start_loop_update(rq);
/*
- * Make sure that misfit_task_load will not be null even if
- * task_h_load() returns 0.
+ * Since we hold rq lock we're safe from concurrent manipulation of
+ * the CSD list. However, this RCU critical section annotates the
+ * fact that we pair with sched_free_group_rcu(), so that we cannot
+ * race with group being freed in the window between removing it
+ * from the list and advancing to the next entry in the list.
*/
- rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1);
-}
+ rcu_read_lock();
+
+ list_for_each_entry_safe(cursor, tmp, &rq->cfsb_csd_list,
+ throttled_csd_list) {
+ list_del_init(&cursor->throttled_csd_list);
-#else /* CONFIG_SMP */
+ if (cfs_rq_throttled(cursor))
+ unthrottle_cfs_rq(cursor);
+ }
-static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
-{
- return !cfs_rq->nr_running;
-}
+ rcu_read_unlock();
-#define UPDATE_TG 0x0
-#define SKIP_AGE_LOAD 0x0
-#define DO_ATTACH 0x0
-#define DO_DETACH 0x0
+ rq_clock_stop_loop_update(rq);
+ rq_unlock(rq, &rf);
+}
-static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
+static inline void __unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
{
- cfs_rq_util_change(cfs_rq, 0);
-}
+ struct rq *rq = rq_of(cfs_rq);
+ bool first;
-static inline void remove_entity_load_avg(struct sched_entity *se) {}
+ if (rq == this_rq()) {
+ unthrottle_cfs_rq(cfs_rq);
+ return;
+ }
-static inline void
-attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
-static inline void
-detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
+ /* Already enqueued */
+ if (SCHED_WARN_ON(!list_empty(&cfs_rq->throttled_csd_list)))
+ return;
-static inline int sched_balance_newidle(struct rq *rq, struct rq_flags *rf)
+ first = list_empty(&rq->cfsb_csd_list);
+ list_add_tail(&cfs_rq->throttled_csd_list, &rq->cfsb_csd_list);
+ if (first)
+ smp_call_function_single_async(cpu_of(rq), &rq->cfsb_csd);
+}
+#else
+static inline void __unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
{
- return 0;
+ unthrottle_cfs_rq(cfs_rq);
}
+#endif
-static inline void
-util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
-
-static inline void
-util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
+static void unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
+{
+ lockdep_assert_rq_held(rq_of(cfs_rq));
-static inline void
-util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p,
- bool task_sleep) {}
-static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
+ if (SCHED_WARN_ON(!cfs_rq_throttled(cfs_rq) ||
+ cfs_rq->runtime_remaining <= 0))
+ return;
-#endif /* CONFIG_SMP */
+ __unthrottle_cfs_rq_async(cfs_rq);
+}
-static void
-place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
+static bool distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
{
- u64 vslice, vruntime = avg_vruntime(cfs_rq);
- s64 lag = 0;
+ int this_cpu = smp_processor_id();
+ u64 runtime, remaining = 1;
+ bool throttled = false;
+ struct cfs_rq *cfs_rq, *tmp;
+ struct rq_flags rf;
+ struct rq *rq;
+ LIST_HEAD(local_unthrottle);
- se->slice = sysctl_sched_base_slice;
- vslice = calc_delta_fair(se->slice, se);
+ rcu_read_lock();
+ list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
+ throttled_list) {
+ rq = rq_of(cfs_rq);
- /*
- * Due to how V is constructed as the weighted average of entities,
- * adding tasks with positive lag, or removing tasks with negative lag
- * will move 'time' backwards, this can screw around with the lag of
- * other tasks.
- *
- * EEVDF: placement strategy #1 / #2
- */
- if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) {
- struct sched_entity *curr = cfs_rq->curr;
- unsigned long load;
-
- lag = se->vlag;
-
- /*
- * If we want to place a task and preserve lag, we have to
- * consider the effect of the new entity on the weighted
- * average and compensate for this, otherwise lag can quickly
- * evaporate.
- *
- * Lag is defined as:
- *
- * lag_i = S - s_i = w_i * (V - v_i)
- *
- * To avoid the 'w_i' term all over the place, we only track
- * the virtual lag:
- *
- * vl_i = V - v_i <=> v_i = V - vl_i
- *
- * And we take V to be the weighted average of all v:
- *
- * V = (\Sum w_j*v_j) / W
- *
- * Where W is: \Sum w_j
- *
- * Then, the weighted average after adding an entity with lag
- * vl_i is given by:
- *
- * V' = (\Sum w_j*v_j + w_i*v_i) / (W + w_i)
- * = (W*V + w_i*(V - vl_i)) / (W + w_i)
- * = (W*V + w_i*V - w_i*vl_i) / (W + w_i)
- * = (V*(W + w_i) - w_i*l) / (W + w_i)
- * = V - w_i*vl_i / (W + w_i)
- *
- * And the actual lag after adding an entity with vl_i is:
- *
- * vl'_i = V' - v_i
- * = V - w_i*vl_i / (W + w_i) - (V - vl_i)
- * = vl_i - w_i*vl_i / (W + w_i)
- *
- * Which is strictly less than vl_i. So in order to preserve lag
- * we should inflate the lag before placement such that the
- * effective lag after placement comes out right.
- *
- * As such, invert the above relation for vl'_i to get the vl_i
- * we need to use such that the lag after placement is the lag
- * we computed before dequeue.
- *
- * vl'_i = vl_i - w_i*vl_i / (W + w_i)
- * = ((W + w_i)*vl_i - w_i*vl_i) / (W + w_i)
- *
- * (W + w_i)*vl'_i = (W + w_i)*vl_i - w_i*vl_i
- * = W*vl_i
- *
- * vl_i = (W + w_i)*vl'_i / W
- */
- load = cfs_rq->avg_load;
- if (curr && curr->on_rq)
- load += scale_load_down(curr->load.weight);
-
- lag *= load + scale_load_down(se->load.weight);
- if (WARN_ON_ONCE(!load))
- load = 1;
- lag = div_s64(lag, load);
- }
-
- se->vruntime = vruntime - lag;
-
- /*
- * When joining the competition; the existing tasks will be,
- * on average, halfway through their slice, as such start tasks
- * off with half a slice to ease into the competition.
- */
- if (sched_feat(PLACE_DEADLINE_INITIAL) && (flags & ENQUEUE_INITIAL))
- vslice /= 2;
-
- /*
- * EEVDF: vd_i = ve_i + r_i/w_i
- */
- se->deadline = se->vruntime + vslice;
-}
-
-static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
-static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq);
-
-static inline bool cfs_bandwidth_used(void);
-
-static void
-enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
-{
- bool curr = cfs_rq->curr == se;
-
- /*
- * If we're the current task, we must renormalise before calling
- * update_curr().
- */
- if (curr)
- place_entity(cfs_rq, se, flags);
-
- update_curr(cfs_rq);
-
- /*
- * When enqueuing a sched_entity, we must:
- * - Update loads to have both entity and cfs_rq synced with now.
- * - For group_entity, update its runnable_weight to reflect the new
- * h_nr_running of its group cfs_rq.
- * - For group_entity, update its weight to reflect the new share of
- * its group cfs_rq
- * - Add its new weight to cfs_rq->load.weight
- */
- update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
- se_update_runnable(se);
- /*
- * XXX update_load_avg() above will have attached us to the pelt sum;
- * but update_cfs_group() here will re-adjust the weight and have to
- * undo/redo all that. Seems wasteful.
- */
- update_cfs_group(se);
-
- /*
- * XXX now that the entity has been re-weighted, and it's lag adjusted,
- * we can place the entity.
- */
- if (!curr)
- place_entity(cfs_rq, se, flags);
-
- account_entity_enqueue(cfs_rq, se);
-
- /* Entity has migrated, no longer consider this task hot */
- if (flags & ENQUEUE_MIGRATED)
- se->exec_start = 0;
-
- check_schedstat_required();
- update_stats_enqueue_fair(cfs_rq, se, flags);
- if (!curr)
- __enqueue_entity(cfs_rq, se);
- se->on_rq = 1;
-
- if (cfs_rq->nr_running == 1) {
- check_enqueue_throttle(cfs_rq);
- if (!throttled_hierarchy(cfs_rq)) {
- list_add_leaf_cfs_rq(cfs_rq);
- } else {
-#ifdef CONFIG_CFS_BANDWIDTH
- struct rq *rq = rq_of(cfs_rq);
-
- if (cfs_rq_throttled(cfs_rq) && !cfs_rq->throttled_clock)
- cfs_rq->throttled_clock = rq_clock(rq);
- if (!cfs_rq->throttled_clock_self)
- cfs_rq->throttled_clock_self = rq_clock(rq);
-#endif
- }
- }
-}
-
-static void __clear_buddies_next(struct sched_entity *se)
-{
- for_each_sched_entity(se) {
- struct cfs_rq *cfs_rq = cfs_rq_of(se);
- if (cfs_rq->next != se)
- break;
-
- cfs_rq->next = NULL;
- }
-}
-
-static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
- if (cfs_rq->next == se)
- __clear_buddies_next(se);
-}
-
-static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
-
-static void
-dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
-{
- int action = UPDATE_TG;
-
- if (entity_is_task(se) && task_on_rq_migrating(task_of(se)))
- action |= DO_DETACH;
-
- /*
- * Update run-time statistics of the 'current'.
- */
- update_curr(cfs_rq);
-
- /*
- * When dequeuing a sched_entity, we must:
- * - Update loads to have both entity and cfs_rq synced with now.
- * - For group_entity, update its runnable_weight to reflect the new
- * h_nr_running of its group cfs_rq.
- * - Subtract its previous weight from cfs_rq->load.weight.
- * - For group entity, update its weight to reflect the new share
- * of its group cfs_rq.
- */
- update_load_avg(cfs_rq, se, action);
- se_update_runnable(se);
-
- update_stats_dequeue_fair(cfs_rq, se, flags);
-
- clear_buddies(cfs_rq, se);
-
- update_entity_lag(cfs_rq, se);
- if (se != cfs_rq->curr)
- __dequeue_entity(cfs_rq, se);
- se->on_rq = 0;
- account_entity_dequeue(cfs_rq, se);
-
- /* return excess runtime on last dequeue */
- return_cfs_rq_runtime(cfs_rq);
-
- update_cfs_group(se);
-
- /*
- * Now advance min_vruntime if @se was the entity holding it back,
- * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
- * put back on, and if we advance min_vruntime, we'll be placed back
- * further than we started -- i.e. we'll be penalized.
- */
- if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
- update_min_vruntime(cfs_rq);
-
- if (cfs_rq->nr_running == 0)
- update_idle_cfs_rq_clock_pelt(cfs_rq);
-}
-
-static void
-set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
- clear_buddies(cfs_rq, se);
-
- /* 'current' is not kept within the tree. */
- if (se->on_rq) {
- /*
- * Any task has to be enqueued before it get to execute on
- * a CPU. So account for the time it spent waiting on the
- * runqueue.
- */
- update_stats_wait_end_fair(cfs_rq, se);
- __dequeue_entity(cfs_rq, se);
- update_load_avg(cfs_rq, se, UPDATE_TG);
- /*
- * HACK, stash a copy of deadline at the point of pick in vlag,
- * which isn't used until dequeue.
- */
- se->vlag = se->deadline;
- }
-
- update_stats_curr_start(cfs_rq, se);
- cfs_rq->curr = se;
-
- /*
- * Track our maximum slice length, if the CPU's load is at
- * least twice that of our own weight (i.e. don't track it
- * when there are only lesser-weight tasks around):
- */
- if (schedstat_enabled() &&
- rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
- struct sched_statistics *stats;
-
- stats = __schedstats_from_se(se);
- __schedstat_set(stats->slice_max,
- max((u64)stats->slice_max,
- se->sum_exec_runtime - se->prev_sum_exec_runtime));
- }
-
- se->prev_sum_exec_runtime = se->sum_exec_runtime;
-}
-
-/*
- * Pick the next process, keeping these things in mind, in this order:
- * 1) keep things fair between processes/task groups
- * 2) pick the "next" process, since someone really wants that to run
- * 3) pick the "last" process, for cache locality
- * 4) do not run the "skip" process, if something else is available
- */
-static struct sched_entity *
-pick_next_entity(struct cfs_rq *cfs_rq)
-{
- /*
- * Enabling NEXT_BUDDY will affect latency but not fairness.
- */
- if (sched_feat(NEXT_BUDDY) &&
- cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))
- return cfs_rq->next;
-
- return pick_eevdf(cfs_rq);
-}
-
-static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
-
-static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
-{
- /*
- * If still on the runqueue then deactivate_task()
- * was not called and update_curr() has to be done:
- */
- if (prev->on_rq)
- update_curr(cfs_rq);
-
- /* throttle cfs_rqs exceeding runtime */
- check_cfs_rq_runtime(cfs_rq);
-
- if (prev->on_rq) {
- update_stats_wait_start_fair(cfs_rq, prev);
- /* Put 'current' back into the tree. */
- __enqueue_entity(cfs_rq, prev);
- /* in !on_rq case, update occurred at dequeue */
- update_load_avg(cfs_rq, prev, 0);
- }
- cfs_rq->curr = NULL;
-}
-
-static void
-entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
-{
- /*
- * Update run-time statistics of the 'current'.
- */
- update_curr(cfs_rq);
-
- /*
- * Ensure that runnable average is periodically updated.
- */
- update_load_avg(cfs_rq, curr, UPDATE_TG);
- update_cfs_group(curr);
-
-#ifdef CONFIG_SCHED_HRTICK
- /*
- * queued ticks are scheduled to match the slice, so don't bother
- * validating it and just reschedule.
- */
- if (queued) {
- resched_curr(rq_of(cfs_rq));
- return;
- }
- /*
- * don't let the period tick interfere with the hrtick preemption
- */
- if (!sched_feat(DOUBLE_TICK) &&
- hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
- return;
-#endif
-}
-
-
-/**************************************************
- * CFS bandwidth control machinery
- */
-
-#ifdef CONFIG_CFS_BANDWIDTH
-
-#ifdef CONFIG_JUMP_LABEL
-static struct static_key __cfs_bandwidth_used;
-
-static inline bool cfs_bandwidth_used(void)
-{
- return static_key_false(&__cfs_bandwidth_used);
-}
-
-void cfs_bandwidth_usage_inc(void)
-{
- static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
-}
-
-void cfs_bandwidth_usage_dec(void)
-{
- static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
-}
-#else /* CONFIG_JUMP_LABEL */
-static bool cfs_bandwidth_used(void)
-{
- return true;
-}
-
-void cfs_bandwidth_usage_inc(void) {}
-void cfs_bandwidth_usage_dec(void) {}
-#endif /* CONFIG_JUMP_LABEL */
-
-/*
- * default period for cfs group bandwidth.
- * default: 0.1s, units: nanoseconds
- */
-static inline u64 default_cfs_period(void)
-{
- return 100000000ULL;
-}
-
-static inline u64 sched_cfs_bandwidth_slice(void)
-{
- return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
-}
-
-/*
- * Replenish runtime according to assigned quota. We use sched_clock_cpu
- * directly instead of rq->clock to avoid adding additional synchronization
- * around rq->lock.
- *
- * requires cfs_b->lock
- */
-void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
-{
- s64 runtime;
-
- if (unlikely(cfs_b->quota == RUNTIME_INF))
- return;
-
- cfs_b->runtime += cfs_b->quota;
- runtime = cfs_b->runtime_snap - cfs_b->runtime;
- if (runtime > 0) {
- cfs_b->burst_time += runtime;
- cfs_b->nr_burst++;
- }
-
- cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);
- cfs_b->runtime_snap = cfs_b->runtime;
-}
-
-static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
-{
- return &tg->cfs_bandwidth;
-}
-
-/* returns 0 on failure to allocate runtime */
-static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
- struct cfs_rq *cfs_rq, u64 target_runtime)
-{
- u64 min_amount, amount = 0;
-
- lockdep_assert_held(&cfs_b->lock);
-
- /* note: this is a positive sum as runtime_remaining <= 0 */
- min_amount = target_runtime - cfs_rq->runtime_remaining;
-
- if (cfs_b->quota == RUNTIME_INF)
- amount = min_amount;
- else {
- start_cfs_bandwidth(cfs_b);
-
- if (cfs_b->runtime > 0) {
- amount = min(cfs_b->runtime, min_amount);
- cfs_b->runtime -= amount;
- cfs_b->idle = 0;
- }
- }
-
- cfs_rq->runtime_remaining += amount;
-
- return cfs_rq->runtime_remaining > 0;
-}
-
-/* returns 0 on failure to allocate runtime */
-static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
-{
- struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
- int ret;
-
- raw_spin_lock(&cfs_b->lock);
- ret = __assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice());
- raw_spin_unlock(&cfs_b->lock);
-
- return ret;
-}
-
-static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
-{
- /* dock delta_exec before expiring quota (as it could span periods) */
- cfs_rq->runtime_remaining -= delta_exec;
-
- if (likely(cfs_rq->runtime_remaining > 0))
- return;
-
- if (cfs_rq->throttled)
- return;
- /*
- * if we're unable to extend our runtime we resched so that the active
- * hierarchy can be throttled
- */
- if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
- resched_curr(rq_of(cfs_rq));
-}
-
-static __always_inline
-void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
-{
- if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
- return;
-
- __account_cfs_rq_runtime(cfs_rq, delta_exec);
-}
-
-static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
-{
- return cfs_bandwidth_used() && cfs_rq->throttled;
-}
-
-/* check whether cfs_rq, or any parent, is throttled */
-static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
-{
- return cfs_bandwidth_used() && cfs_rq->throttle_count;
-}
-
-/*
- * Ensure that neither of the group entities corresponding to src_cpu or
- * dest_cpu are members of a throttled hierarchy when performing group
- * load-balance operations.
- */
-static inline int throttled_lb_pair(struct task_group *tg,
- int src_cpu, int dest_cpu)
-{
- struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
-
- src_cfs_rq = tg->cfs_rq[src_cpu];
- dest_cfs_rq = tg->cfs_rq[dest_cpu];
-
- return throttled_hierarchy(src_cfs_rq) ||
- throttled_hierarchy(dest_cfs_rq);
-}
-
-static int tg_unthrottle_up(struct task_group *tg, void *data)
-{
- struct rq *rq = data;
- struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
-
- cfs_rq->throttle_count--;
- if (!cfs_rq->throttle_count) {
- cfs_rq->throttled_clock_pelt_time += rq_clock_pelt(rq) -
- cfs_rq->throttled_clock_pelt;
-
- /* Add cfs_rq with load or one or more already running entities to the list */
- if (!cfs_rq_is_decayed(cfs_rq))
- list_add_leaf_cfs_rq(cfs_rq);
-
- if (cfs_rq->throttled_clock_self) {
- u64 delta = rq_clock(rq) - cfs_rq->throttled_clock_self;
-
- cfs_rq->throttled_clock_self = 0;
-
- if (SCHED_WARN_ON((s64)delta < 0))
- delta = 0;
-
- cfs_rq->throttled_clock_self_time += delta;
- }
- }
-
- return 0;
-}
-
-static int tg_throttle_down(struct task_group *tg, void *data)
-{
- struct rq *rq = data;
- struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
-
- /* group is entering throttled state, stop time */
- if (!cfs_rq->throttle_count) {
- cfs_rq->throttled_clock_pelt = rq_clock_pelt(rq);
- list_del_leaf_cfs_rq(cfs_rq);
-
- SCHED_WARN_ON(cfs_rq->throttled_clock_self);
- if (cfs_rq->nr_running)
- cfs_rq->throttled_clock_self = rq_clock(rq);
- }
- cfs_rq->throttle_count++;
-
- return 0;
-}
-
-static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
-{
- struct rq *rq = rq_of(cfs_rq);
- struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
- struct sched_entity *se;
- long task_delta, idle_task_delta, dequeue = 1;
-
- raw_spin_lock(&cfs_b->lock);
- /* This will start the period timer if necessary */
- if (__assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) {
- /*
- * We have raced with bandwidth becoming available, and if we
- * actually throttled the timer might not unthrottle us for an
- * entire period. We additionally needed to make sure that any
- * subsequent check_cfs_rq_runtime calls agree not to throttle
- * us, as we may commit to do cfs put_prev+pick_next, so we ask
- * for 1ns of runtime rather than just check cfs_b.
- */
- dequeue = 0;
- } else {
- list_add_tail_rcu(&cfs_rq->throttled_list,
- &cfs_b->throttled_cfs_rq);
- }
- raw_spin_unlock(&cfs_b->lock);
-
- if (!dequeue)
- return false; /* Throttle no longer required. */
-
- se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
-
- /* freeze hierarchy runnable averages while throttled */
- rcu_read_lock();
- walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
- rcu_read_unlock();
-
- task_delta = cfs_rq->h_nr_running;
- idle_task_delta = cfs_rq->idle_h_nr_running;
- for_each_sched_entity(se) {
- struct cfs_rq *qcfs_rq = cfs_rq_of(se);
- /* throttled entity or throttle-on-deactivate */
- if (!se->on_rq)
- goto done;
-
- dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
-
- if (cfs_rq_is_idle(group_cfs_rq(se)))
- idle_task_delta = cfs_rq->h_nr_running;
-
- qcfs_rq->h_nr_running -= task_delta;
- qcfs_rq->idle_h_nr_running -= idle_task_delta;
-
- if (qcfs_rq->load.weight) {
- /* Avoid re-evaluating load for this entity: */
- se = parent_entity(se);
- break;
- }
- }
-
- for_each_sched_entity(se) {
- struct cfs_rq *qcfs_rq = cfs_rq_of(se);
- /* throttled entity or throttle-on-deactivate */
- if (!se->on_rq)
- goto done;
-
- update_load_avg(qcfs_rq, se, 0);
- se_update_runnable(se);
-
- if (cfs_rq_is_idle(group_cfs_rq(se)))
- idle_task_delta = cfs_rq->h_nr_running;
-
- qcfs_rq->h_nr_running -= task_delta;
- qcfs_rq->idle_h_nr_running -= idle_task_delta;
- }
-
- /* At this point se is NULL and we are at root level*/
- sub_nr_running(rq, task_delta);
-
-done:
- /*
- * Note: distribution will already see us throttled via the
- * throttled-list. rq->lock protects completion.
- */
- cfs_rq->throttled = 1;
- SCHED_WARN_ON(cfs_rq->throttled_clock);
- if (cfs_rq->nr_running)
- cfs_rq->throttled_clock = rq_clock(rq);
- return true;
-}
-
-void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
-{
- struct rq *rq = rq_of(cfs_rq);
- struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
- struct sched_entity *se;
- long task_delta, idle_task_delta;
-
- se = cfs_rq->tg->se[cpu_of(rq)];
-
- cfs_rq->throttled = 0;
-
- update_rq_clock(rq);
-
- raw_spin_lock(&cfs_b->lock);
- if (cfs_rq->throttled_clock) {
- cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
- cfs_rq->throttled_clock = 0;
- }
- list_del_rcu(&cfs_rq->throttled_list);
- raw_spin_unlock(&cfs_b->lock);
-
- /* update hierarchical throttle state */
- walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
-
- if (!cfs_rq->load.weight) {
- if (!cfs_rq->on_list)
- return;
- /*
- * Nothing to run but something to decay (on_list)?
- * Complete the branch.
- */
- for_each_sched_entity(se) {
- if (list_add_leaf_cfs_rq(cfs_rq_of(se)))
- break;
- }
- goto unthrottle_throttle;
- }
-
- task_delta = cfs_rq->h_nr_running;
- idle_task_delta = cfs_rq->idle_h_nr_running;
- for_each_sched_entity(se) {
- struct cfs_rq *qcfs_rq = cfs_rq_of(se);
-
- if (se->on_rq)
- break;
- enqueue_entity(qcfs_rq, se, ENQUEUE_WAKEUP);
-
- if (cfs_rq_is_idle(group_cfs_rq(se)))
- idle_task_delta = cfs_rq->h_nr_running;
-
- qcfs_rq->h_nr_running += task_delta;
- qcfs_rq->idle_h_nr_running += idle_task_delta;
-
- /* end evaluation on encountering a throttled cfs_rq */
- if (cfs_rq_throttled(qcfs_rq))
- goto unthrottle_throttle;
- }
-
- for_each_sched_entity(se) {
- struct cfs_rq *qcfs_rq = cfs_rq_of(se);
-
- update_load_avg(qcfs_rq, se, UPDATE_TG);
- se_update_runnable(se);
-
- if (cfs_rq_is_idle(group_cfs_rq(se)))
- idle_task_delta = cfs_rq->h_nr_running;
-
- qcfs_rq->h_nr_running += task_delta;
- qcfs_rq->idle_h_nr_running += idle_task_delta;
-
- /* end evaluation on encountering a throttled cfs_rq */
- if (cfs_rq_throttled(qcfs_rq))
- goto unthrottle_throttle;
- }
-
- /* At this point se is NULL and we are at root level*/
- add_nr_running(rq, task_delta);
-
-unthrottle_throttle:
- assert_list_leaf_cfs_rq(rq);
-
- /* Determine whether we need to wake up potentially idle CPU: */
- if (rq->curr == rq->idle && rq->cfs.nr_running)
- resched_curr(rq);
-}
-
-#ifdef CONFIG_SMP
-static void __cfsb_csd_unthrottle(void *arg)
-{
- struct cfs_rq *cursor, *tmp;
- struct rq *rq = arg;
- struct rq_flags rf;
-
- rq_lock(rq, &rf);
-
- /*
- * Iterating over the list can trigger several call to
- * update_rq_clock() in unthrottle_cfs_rq().
- * Do it once and skip the potential next ones.
- */
- update_rq_clock(rq);
- rq_clock_start_loop_update(rq);
-
- /*
- * Since we hold rq lock we're safe from concurrent manipulation of
- * the CSD list. However, this RCU critical section annotates the
- * fact that we pair with sched_free_group_rcu(), so that we cannot
- * race with group being freed in the window between removing it
- * from the list and advancing to the next entry in the list.
- */
- rcu_read_lock();
-
- list_for_each_entry_safe(cursor, tmp, &rq->cfsb_csd_list,
- throttled_csd_list) {
- list_del_init(&cursor->throttled_csd_list);
-
- if (cfs_rq_throttled(cursor))
- unthrottle_cfs_rq(cursor);
- }
-
- rcu_read_unlock();
-
- rq_clock_stop_loop_update(rq);
- rq_unlock(rq, &rf);
-}
-
-static inline void __unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
-{
- struct rq *rq = rq_of(cfs_rq);
- bool first;
-
- if (rq == this_rq()) {
- unthrottle_cfs_rq(cfs_rq);
- return;
- }
-
- /* Already enqueued */
- if (SCHED_WARN_ON(!list_empty(&cfs_rq->throttled_csd_list)))
- return;
-
- first = list_empty(&rq->cfsb_csd_list);
- list_add_tail(&cfs_rq->throttled_csd_list, &rq->cfsb_csd_list);
- if (first)
- smp_call_function_single_async(cpu_of(rq), &rq->cfsb_csd);
-}
-#else
-static inline void __unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
-{
- unthrottle_cfs_rq(cfs_rq);
-}
-#endif
-
-static void unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
-{
- lockdep_assert_rq_held(rq_of(cfs_rq));
-
- if (SCHED_WARN_ON(!cfs_rq_throttled(cfs_rq) ||
- cfs_rq->runtime_remaining <= 0))
- return;
-
- __unthrottle_cfs_rq_async(cfs_rq);
-}
-
-static bool distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
-{
- int this_cpu = smp_processor_id();
- u64 runtime, remaining = 1;
- bool throttled = false;
- struct cfs_rq *cfs_rq, *tmp;
- struct rq_flags rf;
- struct rq *rq;
- LIST_HEAD(local_unthrottle);
-
- rcu_read_lock();
- list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
- throttled_list) {
- rq = rq_of(cfs_rq);
-
- if (!remaining) {
- throttled = true;
- break;
- }
-
- rq_lock_irqsave(rq, &rf);
- if (!cfs_rq_throttled(cfs_rq))
- goto next;
-
- /* Already queued for async unthrottle */
- if (!list_empty(&cfs_rq->throttled_csd_list))
- goto next;
-
- /* By the above checks, this should never be true */
- SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
-
- raw_spin_lock(&cfs_b->lock);
- runtime = -cfs_rq->runtime_remaining + 1;
- if (runtime > cfs_b->runtime)
- runtime = cfs_b->runtime;
- cfs_b->runtime -= runtime;
- remaining = cfs_b->runtime;
- raw_spin_unlock(&cfs_b->lock);
-
- cfs_rq->runtime_remaining += runtime;
-
- /* we check whether we're throttled above */
- if (cfs_rq->runtime_remaining > 0) {
- if (cpu_of(rq) != this_cpu) {
- unthrottle_cfs_rq_async(cfs_rq);
- } else {
- /*
- * We currently only expect to be unthrottling
- * a single cfs_rq locally.
- */
- SCHED_WARN_ON(!list_empty(&local_unthrottle));
- list_add_tail(&cfs_rq->throttled_csd_list,
- &local_unthrottle);
- }
- } else {
- throttled = true;
- }
-
-next:
- rq_unlock_irqrestore(rq, &rf);
- }
-
- list_for_each_entry_safe(cfs_rq, tmp, &local_unthrottle,
- throttled_csd_list) {
- struct rq *rq = rq_of(cfs_rq);
-
- rq_lock_irqsave(rq, &rf);
-
- list_del_init(&cfs_rq->throttled_csd_list);
-
- if (cfs_rq_throttled(cfs_rq))
- unthrottle_cfs_rq(cfs_rq);
-
- rq_unlock_irqrestore(rq, &rf);
- }
- SCHED_WARN_ON(!list_empty(&local_unthrottle));
-
- rcu_read_unlock();
-
- return throttled;
-}
-
-/*
- * Responsible for refilling a task_group's bandwidth and unthrottling its
- * cfs_rqs as appropriate. If there has been no activity within the last
- * period the timer is deactivated until scheduling resumes; cfs_b->idle is
- * used to track this state.
- */
-static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
-{
- int throttled;
-
- /* no need to continue the timer with no bandwidth constraint */
- if (cfs_b->quota == RUNTIME_INF)
- goto out_deactivate;
-
- throttled = !list_empty(&cfs_b->throttled_cfs_rq);
- cfs_b->nr_periods += overrun;
-
- /* Refill extra burst quota even if cfs_b->idle */
- __refill_cfs_bandwidth_runtime(cfs_b);
-
- /*
- * idle depends on !throttled (for the case of a large deficit), and if
- * we're going inactive then everything else can be deferred
- */
- if (cfs_b->idle && !throttled)
- goto out_deactivate;
-
- if (!throttled) {
- /* mark as potentially idle for the upcoming period */
- cfs_b->idle = 1;
- return 0;
- }
-
- /* account preceding periods in which throttling occurred */
- cfs_b->nr_throttled += overrun;
-
- /*
- * This check is repeated as we release cfs_b->lock while we unthrottle.
- */
- while (throttled && cfs_b->runtime > 0) {
- raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
- /* we can't nest cfs_b->lock while distributing bandwidth */
- throttled = distribute_cfs_runtime(cfs_b);
- raw_spin_lock_irqsave(&cfs_b->lock, flags);
- }
-
- /*
- * While we are ensured activity in the period following an
- * unthrottle, this also covers the case in which the new bandwidth is
- * insufficient to cover the existing bandwidth deficit. (Forcing the
- * timer to remain active while there are any throttled entities.)
- */
- cfs_b->idle = 0;
-
- return 0;
-
-out_deactivate:
- return 1;
-}
-
-/* a cfs_rq won't donate quota below this amount */
-static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
-/* minimum remaining period time to redistribute slack quota */
-static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
-/* how long we wait to gather additional slack before distributing */
-static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
-
-/*
- * Are we near the end of the current quota period?
- *
- * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
- * hrtimer base being cleared by hrtimer_start. In the case of
- * migrate_hrtimers, base is never cleared, so we are fine.
- */
-static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
-{
- struct hrtimer *refresh_timer = &cfs_b->period_timer;
- s64 remaining;
-
- /* if the call-back is running a quota refresh is already occurring */
- if (hrtimer_callback_running(refresh_timer))
- return 1;
-
- /* is a quota refresh about to occur? */
- remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
- if (remaining < (s64)min_expire)
- return 1;
-
- return 0;
-}
-
-static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
-{
- u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
-
- /* if there's a quota refresh soon don't bother with slack */
- if (runtime_refresh_within(cfs_b, min_left))
- return;
-
- /* don't push forwards an existing deferred unthrottle */
- if (cfs_b->slack_started)
- return;
- cfs_b->slack_started = true;
-
- hrtimer_start(&cfs_b->slack_timer,
- ns_to_ktime(cfs_bandwidth_slack_period),
- HRTIMER_MODE_REL);
-}
-
-/* we know any runtime found here is valid as update_curr() precedes return */
-static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
-{
- struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
- s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
-
- if (slack_runtime <= 0)
- return;
-
- raw_spin_lock(&cfs_b->lock);
- if (cfs_b->quota != RUNTIME_INF) {
- cfs_b->runtime += slack_runtime;
-
- /* we are under rq->lock, defer unthrottling using a timer */
- if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
- !list_empty(&cfs_b->throttled_cfs_rq))
- start_cfs_slack_bandwidth(cfs_b);
- }
- raw_spin_unlock(&cfs_b->lock);
-
- /* even if it's not valid for return we don't want to try again */
- cfs_rq->runtime_remaining -= slack_runtime;
-}
-
-static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
-{
- if (!cfs_bandwidth_used())
- return;
-
- if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
- return;
-
- __return_cfs_rq_runtime(cfs_rq);
-}
-
-/*
- * This is done with a timer (instead of inline with bandwidth return) since
- * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
- */
-static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
-{
- u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
- unsigned long flags;
-
- /* confirm we're still not at a refresh boundary */
- raw_spin_lock_irqsave(&cfs_b->lock, flags);
- cfs_b->slack_started = false;
-
- if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
- raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
- return;
- }
-
- if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
- runtime = cfs_b->runtime;
-
- raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
-
- if (!runtime)
- return;
-
- distribute_cfs_runtime(cfs_b);
-}
-
-/*
- * When a group wakes up we want to make sure that its quota is not already
- * expired/exceeded, otherwise it may be allowed to steal additional ticks of
- * runtime as update_curr() throttling can not trigger until it's on-rq.
- */
-static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
-{
- if (!cfs_bandwidth_used())
- return;
-
- /* an active group must be handled by the update_curr()->put() path */
- if (!cfs_rq->runtime_enabled || cfs_rq->curr)
- return;
-
- /* ensure the group is not already throttled */
- if (cfs_rq_throttled(cfs_rq))
- return;
-
- /* update runtime allocation */
- account_cfs_rq_runtime(cfs_rq, 0);
- if (cfs_rq->runtime_remaining <= 0)
- throttle_cfs_rq(cfs_rq);
-}
-
-static void sync_throttle(struct task_group *tg, int cpu)
-{
- struct cfs_rq *pcfs_rq, *cfs_rq;
-
- if (!cfs_bandwidth_used())
- return;
-
- if (!tg->parent)
- return;
-
- cfs_rq = tg->cfs_rq[cpu];
- pcfs_rq = tg->parent->cfs_rq[cpu];
-
- cfs_rq->throttle_count = pcfs_rq->throttle_count;
- cfs_rq->throttled_clock_pelt = rq_clock_pelt(cpu_rq(cpu));
-}
-
-/* conditionally throttle active cfs_rq's from put_prev_entity() */
-static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
-{
- if (!cfs_bandwidth_used())
- return false;
-
- if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
- return false;
-
- /*
- * it's possible for a throttled entity to be forced into a running
- * state (e.g. set_curr_task), in this case we're finished.
- */
- if (cfs_rq_throttled(cfs_rq))
- return true;
-
- return throttle_cfs_rq(cfs_rq);
-}
-
-static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
-{
- struct cfs_bandwidth *cfs_b =
- container_of(timer, struct cfs_bandwidth, slack_timer);
-
- do_sched_cfs_slack_timer(cfs_b);
-
- return HRTIMER_NORESTART;
-}
-
-extern const u64 max_cfs_quota_period;
-
-static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
-{
- struct cfs_bandwidth *cfs_b =
- container_of(timer, struct cfs_bandwidth, period_timer);
- unsigned long flags;
- int overrun;
- int idle = 0;
- int count = 0;
-
- raw_spin_lock_irqsave(&cfs_b->lock, flags);
- for (;;) {
- overrun = hrtimer_forward_now(timer, cfs_b->period);
- if (!overrun)
- break;
-
- idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
-
- if (++count > 3) {
- u64 new, old = ktime_to_ns(cfs_b->period);
-
- /*
- * Grow period by a factor of 2 to avoid losing precision.
- * Precision loss in the quota/period ratio can cause __cfs_schedulable
- * to fail.
- */
- new = old * 2;
- if (new < max_cfs_quota_period) {
- cfs_b->period = ns_to_ktime(new);
- cfs_b->quota *= 2;
- cfs_b->burst *= 2;
-
- pr_warn_ratelimited(
- "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
- smp_processor_id(),
- div_u64(new, NSEC_PER_USEC),
- div_u64(cfs_b->quota, NSEC_PER_USEC));
- } else {
- pr_warn_ratelimited(
- "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
- smp_processor_id(),
- div_u64(old, NSEC_PER_USEC),
- div_u64(cfs_b->quota, NSEC_PER_USEC));
- }
-
- /* reset count so we don't come right back in here */
- count = 0;
- }
- }
- if (idle)
- cfs_b->period_active = 0;
- raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
-
- return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
-}
-
-void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth *parent)
-{
- raw_spin_lock_init(&cfs_b->lock);
- cfs_b->runtime = 0;
- cfs_b->quota = RUNTIME_INF;
- cfs_b->period = ns_to_ktime(default_cfs_period());
- cfs_b->burst = 0;
- cfs_b->hierarchical_quota = parent ? parent->hierarchical_quota : RUNTIME_INF;
-
- INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
- hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
- cfs_b->period_timer.function = sched_cfs_period_timer;
-
- /* Add a random offset so that timers interleave */
- hrtimer_set_expires(&cfs_b->period_timer,
- get_random_u32_below(cfs_b->period));
- hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- cfs_b->slack_timer.function = sched_cfs_slack_timer;
- cfs_b->slack_started = false;
-}
-
-static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
-{
- cfs_rq->runtime_enabled = 0;
- INIT_LIST_HEAD(&cfs_rq->throttled_list);
- INIT_LIST_HEAD(&cfs_rq->throttled_csd_list);
-}
-
-void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
-{
- lockdep_assert_held(&cfs_b->lock);
-
- if (cfs_b->period_active)
- return;
-
- cfs_b->period_active = 1;
- hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
- hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
-}
-
-static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
-{
- int __maybe_unused i;
-
- /* init_cfs_bandwidth() was not called */
- if (!cfs_b->throttled_cfs_rq.next)
- return;
-
- hrtimer_cancel(&cfs_b->period_timer);
- hrtimer_cancel(&cfs_b->slack_timer);
-
- /*
- * It is possible that we still have some cfs_rq's pending on a CSD
- * list, though this race is very rare. In order for this to occur, we
- * must have raced with the last task leaving the group while there
- * exist throttled cfs_rq(s), and the period_timer must have queued the
- * CSD item but the remote cpu has not yet processed it. To handle this,
- * we can simply flush all pending CSD work inline here. We're
- * guaranteed at this point that no additional cfs_rq of this group can
- * join a CSD list.
- */
-#ifdef CONFIG_SMP
- for_each_possible_cpu(i) {
- struct rq *rq = cpu_rq(i);
- unsigned long flags;
-
- if (list_empty(&rq->cfsb_csd_list))
- continue;
-
- local_irq_save(flags);
- __cfsb_csd_unthrottle(rq);
- local_irq_restore(flags);
- }
-#endif
-}
-
-/*
- * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
- *
- * The race is harmless, since modifying bandwidth settings of unhooked group
- * bits doesn't do much.
- */
-
-/* cpu online callback */
-static void __maybe_unused update_runtime_enabled(struct rq *rq)
-{
- struct task_group *tg;
-
- lockdep_assert_rq_held(rq);
-
- rcu_read_lock();
- list_for_each_entry_rcu(tg, &task_groups, list) {
- struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
- struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
-
- raw_spin_lock(&cfs_b->lock);
- cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
- raw_spin_unlock(&cfs_b->lock);
- }
- rcu_read_unlock();
-}
-
-/* cpu offline callback */
-static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
-{
- struct task_group *tg;
-
- lockdep_assert_rq_held(rq);
-
- /*
- * The rq clock has already been updated in the
- * set_rq_offline(), so we should skip updating
- * the rq clock again in unthrottle_cfs_rq().
- */
- rq_clock_start_loop_update(rq);
-
- rcu_read_lock();
- list_for_each_entry_rcu(tg, &task_groups, list) {
- struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
-
- if (!cfs_rq->runtime_enabled)
- continue;
-
- /*
- * clock_task is not advancing so we just need to make sure
- * there's some valid quota amount
- */
- cfs_rq->runtime_remaining = 1;
- /*
- * Offline rq is schedulable till CPU is completely disabled
- * in take_cpu_down(), so we prevent new cfs throttling here.
- */
- cfs_rq->runtime_enabled = 0;
-
- if (cfs_rq_throttled(cfs_rq))
- unthrottle_cfs_rq(cfs_rq);
- }
- rcu_read_unlock();
-
- rq_clock_stop_loop_update(rq);
-}
-
-bool cfs_task_bw_constrained(struct task_struct *p)
-{
- struct cfs_rq *cfs_rq = task_cfs_rq(p);
-
- if (!cfs_bandwidth_used())
- return false;
-
- if (cfs_rq->runtime_enabled ||
- tg_cfs_bandwidth(cfs_rq->tg)->hierarchical_quota != RUNTIME_INF)
- return true;
-
- return false;
-}
-
-#ifdef CONFIG_NO_HZ_FULL
-/* called from pick_next_task_fair() */
-static void sched_fair_update_stop_tick(struct rq *rq, struct task_struct *p)
-{
- int cpu = cpu_of(rq);
-
- if (!sched_feat(HZ_BW) || !cfs_bandwidth_used())
- return;
-
- if (!tick_nohz_full_cpu(cpu))
- return;
-
- if (rq->nr_running != 1)
- return;
-
- /*
- * We know there is only one task runnable and we've just picked it. The
- * normal enqueue path will have cleared TICK_DEP_BIT_SCHED if we will
- * be otherwise able to stop the tick. Just need to check if we are using
- * bandwidth control.
- */
- if (cfs_task_bw_constrained(p))
- tick_nohz_dep_set_cpu(cpu, TICK_DEP_BIT_SCHED);
-}
-#endif
-
-#else /* CONFIG_CFS_BANDWIDTH */
-
-static inline bool cfs_bandwidth_used(void)
-{
- return false;
-}
-
-static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
-static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
-static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
-static inline void sync_throttle(struct task_group *tg, int cpu) {}
-static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
-
-static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
-{
- return 0;
-}
-
-static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
-{
- return 0;
-}
-
-static inline int throttled_lb_pair(struct task_group *tg,
- int src_cpu, int dest_cpu)
-{
- return 0;
-}
-
-#ifdef CONFIG_FAIR_GROUP_SCHED
-void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth *parent) {}
-static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
-#endif
-
-static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
-{
- return NULL;
-}
-static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
-static inline void update_runtime_enabled(struct rq *rq) {}
-static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
-#ifdef CONFIG_CGROUP_SCHED
-bool cfs_task_bw_constrained(struct task_struct *p)
-{
- return false;
-}
-#endif
-#endif /* CONFIG_CFS_BANDWIDTH */
-
-#if !defined(CONFIG_CFS_BANDWIDTH) || !defined(CONFIG_NO_HZ_FULL)
-static inline void sched_fair_update_stop_tick(struct rq *rq, struct task_struct *p) {}
-#endif
-
-/**************************************************
- * CFS operations on tasks:
- */
-
-#ifdef CONFIG_SCHED_HRTICK
-static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
-{
- struct sched_entity *se = &p->se;
-
- SCHED_WARN_ON(task_rq(p) != rq);
-
- if (rq->cfs.h_nr_running > 1) {
- u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
- u64 slice = se->slice;
- s64 delta = slice - ran;
-
- if (delta < 0) {
- if (task_current(rq, p))
- resched_curr(rq);
- return;
- }
- hrtick_start(rq, delta);
- }
-}
-
-/*
- * called from enqueue/dequeue and updates the hrtick when the
- * current task is from our class and nr_running is low enough
- * to matter.
- */
-static void hrtick_update(struct rq *rq)
-{
- struct task_struct *curr = rq->curr;
-
- if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class)
- return;
-
- hrtick_start_fair(rq, curr);
-}
-#else /* !CONFIG_SCHED_HRTICK */
-static inline void
-hrtick_start_fair(struct rq *rq, struct task_struct *p)
-{
-}
-
-static inline void hrtick_update(struct rq *rq)
-{
-}
-#endif
-
-#ifdef CONFIG_SMP
-static inline bool cpu_overutilized(int cpu)
-{
- unsigned long rq_util_min, rq_util_max;
-
- if (!sched_energy_enabled())
- return false;
-
- rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
- rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
-
- /* Return true only if the utilization doesn't fit CPU's capacity */
- return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
-}
-
-/*
- * overutilized value make sense only if EAS is enabled
- */
-static inline bool is_rd_overutilized(struct root_domain *rd)
-{
- return !sched_energy_enabled() || READ_ONCE(rd->overutilized);
-}
-
-static inline void set_rd_overutilized(struct root_domain *rd, bool flag)
-{
- if (!sched_energy_enabled())
- return;
-
- WRITE_ONCE(rd->overutilized, flag);
- trace_sched_overutilized_tp(rd, flag);
-}
-
-static inline void check_update_overutilized_status(struct rq *rq)
-{
- /*
- * overutilized field is used for load balancing decisions only
- * if energy aware scheduler is being used
- */
-
- if (!is_rd_overutilized(rq->rd) && cpu_overutilized(rq->cpu))
- set_rd_overutilized(rq->rd, 1);
-}
-#else
-static inline void check_update_overutilized_status(struct rq *rq) { }
-#endif
-
-/* Runqueue only has SCHED_IDLE tasks enqueued */
-static int sched_idle_rq(struct rq *rq)
-{
- return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running &&
- rq->nr_running);
-}
-
-#ifdef CONFIG_SMP
-static int sched_idle_cpu(int cpu)
-{
- return sched_idle_rq(cpu_rq(cpu));
-}
-#endif
-
-/*
- * The enqueue_task method is called before nr_running is
- * increased. Here we update the fair scheduling stats and
- * then put the task into the rbtree:
- */
-static void
-enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
-{
- struct cfs_rq *cfs_rq;
- struct sched_entity *se = &p->se;
- int idle_h_nr_running = task_has_idle_policy(p);
- int task_new = !(flags & ENQUEUE_WAKEUP);
-
- /*
- * The code below (indirectly) updates schedutil which looks at
- * the cfs_rq utilization to select a frequency.
- * Let's add the task's estimated utilization to the cfs_rq's
- * estimated utilization, before we update schedutil.
- */
- util_est_enqueue(&rq->cfs, p);
-
- /*
- * If in_iowait is set, the code below may not trigger any cpufreq
- * utilization updates, so do it here explicitly with the IOWAIT flag
- * passed.
- */
- if (p->in_iowait)
- cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
-
- for_each_sched_entity(se) {
- if (se->on_rq)
- break;
- cfs_rq = cfs_rq_of(se);
- enqueue_entity(cfs_rq, se, flags);
-
- cfs_rq->h_nr_running++;
- cfs_rq->idle_h_nr_running += idle_h_nr_running;
-
- if (cfs_rq_is_idle(cfs_rq))
- idle_h_nr_running = 1;
-
- /* end evaluation on encountering a throttled cfs_rq */
- if (cfs_rq_throttled(cfs_rq))
- goto enqueue_throttle;
-
- flags = ENQUEUE_WAKEUP;
- }
-
- for_each_sched_entity(se) {
- cfs_rq = cfs_rq_of(se);
-
- update_load_avg(cfs_rq, se, UPDATE_TG);
- se_update_runnable(se);
- update_cfs_group(se);
-
- cfs_rq->h_nr_running++;
- cfs_rq->idle_h_nr_running += idle_h_nr_running;
-
- if (cfs_rq_is_idle(cfs_rq))
- idle_h_nr_running = 1;
-
- /* end evaluation on encountering a throttled cfs_rq */
- if (cfs_rq_throttled(cfs_rq))
- goto enqueue_throttle;
- }
-
- /* At this point se is NULL and we are at root level*/
- add_nr_running(rq, 1);
-
- /*
- * Since new tasks are assigned an initial util_avg equal to
- * half of the spare capacity of their CPU, tiny tasks have the
- * ability to cross the overutilized threshold, which will
- * result in the load balancer ruining all the task placement
- * done by EAS. As a way to mitigate that effect, do not account
- * for the first enqueue operation of new tasks during the
- * overutilized flag detection.
- *
- * A better way of solving this problem would be to wait for
- * the PELT signals of tasks to converge before taking them
- * into account, but that is not straightforward to implement,
- * and the following generally works well enough in practice.
- */
- if (!task_new)
- check_update_overutilized_status(rq);
-
-enqueue_throttle:
- assert_list_leaf_cfs_rq(rq);
-
- hrtick_update(rq);
-}
-
-static void set_next_buddy(struct sched_entity *se);
-
-/*
- * The dequeue_task method is called before nr_running is
- * decreased. We remove the task from the rbtree and
- * update the fair scheduling stats:
- */
-static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
-{
- struct cfs_rq *cfs_rq;
- struct sched_entity *se = &p->se;
- int task_sleep = flags & DEQUEUE_SLEEP;
- int idle_h_nr_running = task_has_idle_policy(p);
- bool was_sched_idle = sched_idle_rq(rq);
-
- util_est_dequeue(&rq->cfs, p);
-
- for_each_sched_entity(se) {
- cfs_rq = cfs_rq_of(se);
- dequeue_entity(cfs_rq, se, flags);
-
- cfs_rq->h_nr_running--;
- cfs_rq->idle_h_nr_running -= idle_h_nr_running;
-
- if (cfs_rq_is_idle(cfs_rq))
- idle_h_nr_running = 1;
-
- /* end evaluation on encountering a throttled cfs_rq */
- if (cfs_rq_throttled(cfs_rq))
- goto dequeue_throttle;
-
- /* Don't dequeue parent if it has other entities besides us */
- if (cfs_rq->load.weight) {
- /* Avoid re-evaluating load for this entity: */
- se = parent_entity(se);
- /*
- * Bias pick_next to pick a task from this cfs_rq, as
- * p is sleeping when it is within its sched_slice.
- */
- if (task_sleep && se && !throttled_hierarchy(cfs_rq))
- set_next_buddy(se);
- break;
- }
- flags |= DEQUEUE_SLEEP;
- }
-
- for_each_sched_entity(se) {
- cfs_rq = cfs_rq_of(se);
-
- update_load_avg(cfs_rq, se, UPDATE_TG);
- se_update_runnable(se);
- update_cfs_group(se);
-
- cfs_rq->h_nr_running--;
- cfs_rq->idle_h_nr_running -= idle_h_nr_running;
-
- if (cfs_rq_is_idle(cfs_rq))
- idle_h_nr_running = 1;
-
- /* end evaluation on encountering a throttled cfs_rq */
- if (cfs_rq_throttled(cfs_rq))
- goto dequeue_throttle;
-
- }
-
- /* At this point se is NULL and we are at root level*/
- sub_nr_running(rq, 1);
-
- /* balance early to pull high priority tasks */
- if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
- rq->next_balance = jiffies;
-
-dequeue_throttle:
- util_est_update(&rq->cfs, p, task_sleep);
- hrtick_update(rq);
-}
-
-#ifdef CONFIG_SMP
-
-/* Working cpumask for: sched_balance_rq(), sched_balance_newidle(). */
-static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
-static DEFINE_PER_CPU(cpumask_var_t, select_rq_mask);
-static DEFINE_PER_CPU(cpumask_var_t, should_we_balance_tmpmask);
-
-#ifdef CONFIG_NO_HZ_COMMON
-
-static struct {
- cpumask_var_t idle_cpus_mask;
- atomic_t nr_cpus;
- int has_blocked; /* Idle CPUS has blocked load */
- int needs_update; /* Newly idle CPUs need their next_balance collated */
- unsigned long next_balance; /* in jiffy units */
- unsigned long next_blocked; /* Next update of blocked load in jiffies */
-} nohz ____cacheline_aligned;
-
-#endif /* CONFIG_NO_HZ_COMMON */
-
-static unsigned long cpu_load(struct rq *rq)
-{
- return cfs_rq_load_avg(&rq->cfs);
-}
-
-/*
- * cpu_load_without - compute CPU load without any contributions from *p
- * @cpu: the CPU which load is requested
- * @p: the task which load should be discounted
- *
- * The load of a CPU is defined by the load of tasks currently enqueued on that
- * CPU as well as tasks which are currently sleeping after an execution on that
- * CPU.
- *
- * This method returns the load of the specified CPU by discounting the load of
- * the specified task, whenever the task is currently contributing to the CPU
- * load.
- */
-static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
-{
- struct cfs_rq *cfs_rq;
- unsigned int load;
-
- /* Task has no contribution or is new */
- if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
- return cpu_load(rq);
-
- cfs_rq = &rq->cfs;
- load = READ_ONCE(cfs_rq->avg.load_avg);
-
- /* Discount task's util from CPU's util */
- lsub_positive(&load, task_h_load(p));
-
- return load;
-}
-
-static unsigned long cpu_runnable(struct rq *rq)
-{
- return cfs_rq_runnable_avg(&rq->cfs);
-}
-
-static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
-{
- struct cfs_rq *cfs_rq;
- unsigned int runnable;
-
- /* Task has no contribution or is new */
- if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
- return cpu_runnable(rq);
-
- cfs_rq = &rq->cfs;
- runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
-
- /* Discount task's runnable from CPU's runnable */
- lsub_positive(&runnable, p->se.avg.runnable_avg);
-
- return runnable;
-}
-
-static unsigned long capacity_of(int cpu)
-{
- return cpu_rq(cpu)->cpu_capacity;
-}
-
-static void record_wakee(struct task_struct *p)
-{
- /*
- * Only decay a single time; tasks that have less then 1 wakeup per
- * jiffy will not have built up many flips.
- */
- if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
- current->wakee_flips >>= 1;
- current->wakee_flip_decay_ts = jiffies;
- }
-
- if (current->last_wakee != p) {
- current->last_wakee = p;
- current->wakee_flips++;
- }
-}
-
-/*
- * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
- *
- * A waker of many should wake a different task than the one last awakened
- * at a frequency roughly N times higher than one of its wakees.
- *
- * In order to determine whether we should let the load spread vs consolidating
- * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
- * partner, and a factor of lls_size higher frequency in the other.
- *
- * With both conditions met, we can be relatively sure that the relationship is
- * non-monogamous, with partner count exceeding socket size.
- *
- * Waker/wakee being client/server, worker/dispatcher, interrupt source or
- * whatever is irrelevant, spread criteria is apparent partner count exceeds
- * socket size.
- */
-static int wake_wide(struct task_struct *p)
-{
- unsigned int master = current->wakee_flips;
- unsigned int slave = p->wakee_flips;
- int factor = __this_cpu_read(sd_llc_size);
-
- if (master < slave)
- swap(master, slave);
- if (slave < factor || master < slave * factor)
- return 0;
- return 1;
-}
-
-/*
- * The purpose of wake_affine() is to quickly determine on which CPU we can run
- * soonest. For the purpose of speed we only consider the waking and previous
- * CPU.
- *
- * wake_affine_idle() - only considers 'now', it check if the waking CPU is
- * cache-affine and is (or will be) idle.
- *
- * wake_affine_weight() - considers the weight to reflect the average
- * scheduling latency of the CPUs. This seems to work
- * for the overloaded case.
- */
-static int
-wake_affine_idle(int this_cpu, int prev_cpu, int sync)
-{
- /*
- * If this_cpu is idle, it implies the wakeup is from interrupt
- * context. Only allow the move if cache is shared. Otherwise an
- * interrupt intensive workload could force all tasks onto one
- * node depending on the IO topology or IRQ affinity settings.
- *
- * If the prev_cpu is idle and cache affine then avoid a migration.
- * There is no guarantee that the cache hot data from an interrupt
- * is more important than cache hot data on the prev_cpu and from
- * a cpufreq perspective, it's better to have higher utilisation
- * on one CPU.
- */
- if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
- return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
-
- if (sync && cpu_rq(this_cpu)->nr_running == 1)
- return this_cpu;
-
- if (available_idle_cpu(prev_cpu))
- return prev_cpu;
-
- return nr_cpumask_bits;
-}
-
-static int
-wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
- int this_cpu, int prev_cpu, int sync)
-{
- s64 this_eff_load, prev_eff_load;
- unsigned long task_load;
-
- this_eff_load = cpu_load(cpu_rq(this_cpu));
-
- if (sync) {
- unsigned long current_load = task_h_load(current);
-
- if (current_load > this_eff_load)
- return this_cpu;
-
- this_eff_load -= current_load;
- }
-
- task_load = task_h_load(p);
-
- this_eff_load += task_load;
- if (sched_feat(WA_BIAS))
- this_eff_load *= 100;
- this_eff_load *= capacity_of(prev_cpu);
-
- prev_eff_load = cpu_load(cpu_rq(prev_cpu));
- prev_eff_load -= task_load;
- if (sched_feat(WA_BIAS))
- prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
- prev_eff_load *= capacity_of(this_cpu);
-
- /*
- * If sync, adjust the weight of prev_eff_load such that if
- * prev_eff == this_eff that select_idle_sibling() will consider
- * stacking the wakee on top of the waker if no other CPU is
- * idle.
- */
- if (sync)
- prev_eff_load += 1;
-
- return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
-}
-
-static int wake_affine(struct sched_domain *sd, struct task_struct *p,
- int this_cpu, int prev_cpu, int sync)
-{
- int target = nr_cpumask_bits;
-
- if (sched_feat(WA_IDLE))
- target = wake_affine_idle(this_cpu, prev_cpu, sync);
-
- if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
- target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
-
- schedstat_inc(p->stats.nr_wakeups_affine_attempts);
- if (target != this_cpu)
- return prev_cpu;
-
- schedstat_inc(sd->ttwu_move_affine);
- schedstat_inc(p->stats.nr_wakeups_affine);
- return target;
-}
-
-static struct sched_group *
-sched_balance_find_dst_group(struct sched_domain *sd, struct task_struct *p, int this_cpu);
-
-/*
- * sched_balance_find_dst_group_cpu - find the idlest CPU among the CPUs in the group.
- */
-static int
-sched_balance_find_dst_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
-{
- unsigned long load, min_load = ULONG_MAX;
- unsigned int min_exit_latency = UINT_MAX;
- u64 latest_idle_timestamp = 0;
- int least_loaded_cpu = this_cpu;
- int shallowest_idle_cpu = -1;
- int i;
-
- /* Check if we have any choice: */
- if (group->group_weight == 1)
- return cpumask_first(sched_group_span(group));
-
- /* Traverse only the allowed CPUs */
- for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
- struct rq *rq = cpu_rq(i);
-
- if (!sched_core_cookie_match(rq, p))
- continue;
-
- if (sched_idle_cpu(i))
- return i;
-
- if (available_idle_cpu(i)) {
- struct cpuidle_state *idle = idle_get_state(rq);
- if (idle && idle->exit_latency < min_exit_latency) {
- /*
- * We give priority to a CPU whose idle state
- * has the smallest exit latency irrespective
- * of any idle timestamp.
- */
- min_exit_latency = idle->exit_latency;
- latest_idle_timestamp = rq->idle_stamp;
- shallowest_idle_cpu = i;
- } else if ((!idle || idle->exit_latency == min_exit_latency) &&
- rq->idle_stamp > latest_idle_timestamp) {
- /*
- * If equal or no active idle state, then
- * the most recently idled CPU might have
- * a warmer cache.
- */
- latest_idle_timestamp = rq->idle_stamp;
- shallowest_idle_cpu = i;
- }
- } else if (shallowest_idle_cpu == -1) {
- load = cpu_load(cpu_rq(i));
- if (load < min_load) {
- min_load = load;
- least_loaded_cpu = i;
- }
- }
- }
-
- return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
-}
-
-static inline int sched_balance_find_dst_cpu(struct sched_domain *sd, struct task_struct *p,
- int cpu, int prev_cpu, int sd_flag)
-{
- int new_cpu = cpu;
-
- if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
- return prev_cpu;
-
- /*
- * We need task's util for cpu_util_without, sync it up to
- * prev_cpu's last_update_time.
- */
- if (!(sd_flag & SD_BALANCE_FORK))
- sync_entity_load_avg(&p->se);
-
- while (sd) {
- struct sched_group *group;
- struct sched_domain *tmp;
- int weight;
-
- if (!(sd->flags & sd_flag)) {
- sd = sd->child;
- continue;
- }
-
- group = sched_balance_find_dst_group(sd, p, cpu);
- if (!group) {
- sd = sd->child;
- continue;
- }
-
- new_cpu = sched_balance_find_dst_group_cpu(group, p, cpu);
- if (new_cpu == cpu) {
- /* Now try balancing at a lower domain level of 'cpu': */
- sd = sd->child;
- continue;
- }
-
- /* Now try balancing at a lower domain level of 'new_cpu': */
- cpu = new_cpu;
- weight = sd->span_weight;
- sd = NULL;
- for_each_domain(cpu, tmp) {
- if (weight <= tmp->span_weight)
- break;
- if (tmp->flags & sd_flag)
- sd = tmp;
- }
- }
-
- return new_cpu;
-}
-
-static inline int __select_idle_cpu(int cpu, struct task_struct *p)
-{
- if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) &&
- sched_cpu_cookie_match(cpu_rq(cpu), p))
- return cpu;
-
- return -1;
-}
-
-#ifdef CONFIG_SCHED_SMT
-DEFINE_STATIC_KEY_FALSE(sched_smt_present);
-EXPORT_SYMBOL_GPL(sched_smt_present);
-
-static inline void set_idle_cores(int cpu, int val)
-{
- struct sched_domain_shared *sds;
-
- sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
- if (sds)
- WRITE_ONCE(sds->has_idle_cores, val);
-}
-
-static inline bool test_idle_cores(int cpu)
-{
- struct sched_domain_shared *sds;
-
- sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
- if (sds)
- return READ_ONCE(sds->has_idle_cores);
-
- return false;
-}
-
-/*
- * Scans the local SMT mask to see if the entire core is idle, and records this
- * information in sd_llc_shared->has_idle_cores.
- *
- * Since SMT siblings share all cache levels, inspecting this limited remote
- * state should be fairly cheap.
- */
-void __update_idle_core(struct rq *rq)
-{
- int core = cpu_of(rq);
- int cpu;
-
- rcu_read_lock();
- if (test_idle_cores(core))
- goto unlock;
-
- for_each_cpu(cpu, cpu_smt_mask(core)) {
- if (cpu == core)
- continue;
-
- if (!available_idle_cpu(cpu))
- goto unlock;
- }
-
- set_idle_cores(core, 1);
-unlock:
- rcu_read_unlock();
-}
-
-/*
- * Scan the entire LLC domain for idle cores; this dynamically switches off if
- * there are no idle cores left in the system; tracked through
- * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
- */
-static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
-{
- bool idle = true;
- int cpu;
-
- for_each_cpu(cpu, cpu_smt_mask(core)) {
- if (!available_idle_cpu(cpu)) {
- idle = false;
- if (*idle_cpu == -1) {
- if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, cpus)) {
- *idle_cpu = cpu;
- break;
- }
- continue;
- }
- break;
- }
- if (*idle_cpu == -1 && cpumask_test_cpu(cpu, cpus))
- *idle_cpu = cpu;
- }
-
- if (idle)
- return core;
-
- cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
- return -1;
-}
-
-/*
- * Scan the local SMT mask for idle CPUs.
- */
-static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
-{
- int cpu;
-
- for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
- if (cpu == target)
- continue;
- /*
- * Check if the CPU is in the LLC scheduling domain of @target.
- * Due to isolcpus, there is no guarantee that all the siblings are in the domain.
- */
- if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
- continue;
- if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
- return cpu;
- }
-
- return -1;
-}
-
-#else /* CONFIG_SCHED_SMT */
-
-static inline void set_idle_cores(int cpu, int val)
-{
-}
-
-static inline bool test_idle_cores(int cpu)
-{
- return false;
-}
-
-static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
-{
- return __select_idle_cpu(core, p);
-}
-
-static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
-{
- return -1;
-}
-
-#endif /* CONFIG_SCHED_SMT */
-
-/*
- * Scan the LLC domain for idle CPUs; this is dynamically regulated by
- * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
- * average idle time for this rq (as found in rq->avg_idle).
- */
-static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool has_idle_core, int target)
-{
- struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
- int i, cpu, idle_cpu = -1, nr = INT_MAX;
- struct sched_domain_shared *sd_share;
-
- cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
-
- if (sched_feat(SIS_UTIL)) {
- sd_share = rcu_dereference(per_cpu(sd_llc_shared, target));
- if (sd_share) {
- /* because !--nr is the condition to stop scan */
- nr = READ_ONCE(sd_share->nr_idle_scan) + 1;
- /* overloaded LLC is unlikely to have idle cpu/core */
- if (nr == 1)
- return -1;
- }
- }
-
- if (static_branch_unlikely(&sched_cluster_active)) {
- struct sched_group *sg = sd->groups;
-
- if (sg->flags & SD_CLUSTER) {
- for_each_cpu_wrap(cpu, sched_group_span(sg), target + 1) {
- if (!cpumask_test_cpu(cpu, cpus))
- continue;
-
- if (has_idle_core) {
- i = select_idle_core(p, cpu, cpus, &idle_cpu);
- if ((unsigned int)i < nr_cpumask_bits)
- return i;
- } else {
- if (--nr <= 0)
- return -1;
- idle_cpu = __select_idle_cpu(cpu, p);
- if ((unsigned int)idle_cpu < nr_cpumask_bits)
- return idle_cpu;
- }
- }
- cpumask_andnot(cpus, cpus, sched_group_span(sg));
- }
- }
-
- for_each_cpu_wrap(cpu, cpus, target + 1) {
- if (has_idle_core) {
- i = select_idle_core(p, cpu, cpus, &idle_cpu);
- if ((unsigned int)i < nr_cpumask_bits)
- return i;
-
- } else {
- if (--nr <= 0)
- return -1;
- idle_cpu = __select_idle_cpu(cpu, p);
- if ((unsigned int)idle_cpu < nr_cpumask_bits)
- break;
- }
- }
-
- if (has_idle_core)
- set_idle_cores(target, false);
-
- return idle_cpu;
-}
-
-/*
- * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
- * the task fits. If no CPU is big enough, but there are idle ones, try to
- * maximize capacity.
- */
-static int
-select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
-{
- unsigned long task_util, util_min, util_max, best_cap = 0;
- int fits, best_fits = 0;
- int cpu, best_cpu = -1;
- struct cpumask *cpus;
-
- cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
- cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
-
- task_util = task_util_est(p);
- util_min = uclamp_eff_value(p, UCLAMP_MIN);
- util_max = uclamp_eff_value(p, UCLAMP_MAX);
-
- for_each_cpu_wrap(cpu, cpus, target) {
- unsigned long cpu_cap = capacity_of(cpu);
-
- if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
- continue;
-
- fits = util_fits_cpu(task_util, util_min, util_max, cpu);
-
- /* This CPU fits with all requirements */
- if (fits > 0)
- return cpu;
- /*
- * Only the min performance hint (i.e. uclamp_min) doesn't fit.
- * Look for the CPU with best capacity.
- */
- else if (fits < 0)
- cpu_cap = arch_scale_cpu_capacity(cpu) - thermal_load_avg(cpu_rq(cpu));
-
- /*
- * First, select CPU which fits better (-1 being better than 0).
- * Then, select the one with best capacity at same level.
- */
- if ((fits < best_fits) ||
- ((fits == best_fits) && (cpu_cap > best_cap))) {
- best_cap = cpu_cap;
- best_cpu = cpu;
- best_fits = fits;
- }
- }
-
- return best_cpu;
-}
-
-static inline bool asym_fits_cpu(unsigned long util,
- unsigned long util_min,
- unsigned long util_max,
- int cpu)
-{
- if (sched_asym_cpucap_active())
- /*
- * Return true only if the cpu fully fits the task requirements
- * which include the utilization and the performance hints.
- */
- return (util_fits_cpu(util, util_min, util_max, cpu) > 0);
-
- return true;
-}
-
-/*
- * Try and locate an idle core/thread in the LLC cache domain.
- */
-static int select_idle_sibling(struct task_struct *p, int prev, int target)
-{
- bool has_idle_core = false;
- struct sched_domain *sd;
- unsigned long task_util, util_min, util_max;
- int i, recent_used_cpu, prev_aff = -1;
-
- /*
- * On asymmetric system, update task utilization because we will check
- * that the task fits with CPU's capacity.
- */
- if (sched_asym_cpucap_active()) {
- sync_entity_load_avg(&p->se);
- task_util = task_util_est(p);
- util_min = uclamp_eff_value(p, UCLAMP_MIN);
- util_max = uclamp_eff_value(p, UCLAMP_MAX);
- }
-
- /*
- * per-cpu select_rq_mask usage
- */
- lockdep_assert_irqs_disabled();
-
- if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
- asym_fits_cpu(task_util, util_min, util_max, target))
- return target;
-
- /*
- * If the previous CPU is cache affine and idle, don't be stupid:
- */
- if (prev != target && cpus_share_cache(prev, target) &&
- (available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
- asym_fits_cpu(task_util, util_min, util_max, prev)) {
-
- if (!static_branch_unlikely(&sched_cluster_active) ||
- cpus_share_resources(prev, target))
- return prev;
-
- prev_aff = prev;
- }
-
- /*
- * Allow a per-cpu kthread to stack with the wakee if the
- * kworker thread and the tasks previous CPUs are the same.
- * The assumption is that the wakee queued work for the
- * per-cpu kthread that is now complete and the wakeup is
- * essentially a sync wakeup. An obvious example of this
- * pattern is IO completions.
- */
- if (is_per_cpu_kthread(current) &&
- in_task() &&
- prev == smp_processor_id() &&
- this_rq()->nr_running <= 1 &&
- asym_fits_cpu(task_util, util_min, util_max, prev)) {
- return prev;
- }
-
- /* Check a recently used CPU as a potential idle candidate: */
- recent_used_cpu = p->recent_used_cpu;
- p->recent_used_cpu = prev;
- if (recent_used_cpu != prev &&
- recent_used_cpu != target &&
- cpus_share_cache(recent_used_cpu, target) &&
- (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
- cpumask_test_cpu(recent_used_cpu, p->cpus_ptr) &&
- asym_fits_cpu(task_util, util_min, util_max, recent_used_cpu)) {
-
- if (!static_branch_unlikely(&sched_cluster_active) ||
- cpus_share_resources(recent_used_cpu, target))
- return recent_used_cpu;
-
- } else {
- recent_used_cpu = -1;
- }
-
- /*
- * For asymmetric CPU capacity systems, our domain of interest is
- * sd_asym_cpucapacity rather than sd_llc.
- */
- if (sched_asym_cpucap_active()) {
- sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
- /*
- * On an asymmetric CPU capacity system where an exclusive
- * cpuset defines a symmetric island (i.e. one unique
- * capacity_orig value through the cpuset), the key will be set
- * but the CPUs within that cpuset will not have a domain with
- * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
- * capacity path.
- */
- if (sd) {
- i = select_idle_capacity(p, sd, target);
- return ((unsigned)i < nr_cpumask_bits) ? i : target;
- }
- }
-
- sd = rcu_dereference(per_cpu(sd_llc, target));
- if (!sd)
- return target;
-
- if (sched_smt_active()) {
- has_idle_core = test_idle_cores(target);
-
- if (!has_idle_core && cpus_share_cache(prev, target)) {
- i = select_idle_smt(p, sd, prev);
- if ((unsigned int)i < nr_cpumask_bits)
- return i;
- }
- }
-
- i = select_idle_cpu(p, sd, has_idle_core, target);
- if ((unsigned)i < nr_cpumask_bits)
- return i;
-
- /*
- * For cluster machines which have lower sharing cache like L2 or
- * LLC Tag, we tend to find an idle CPU in the target's cluster
- * first. But prev_cpu or recent_used_cpu may also be a good candidate,
- * use them if possible when no idle CPU found in select_idle_cpu().
- */
- if ((unsigned int)prev_aff < nr_cpumask_bits)
- return prev_aff;
- if ((unsigned int)recent_used_cpu < nr_cpumask_bits)
- return recent_used_cpu;
-
- return target;
-}
-
-/**
- * cpu_util() - Estimates the amount of CPU capacity used by CFS tasks.
- * @cpu: the CPU to get the utilization for
- * @p: task for which the CPU utilization should be predicted or NULL
- * @dst_cpu: CPU @p migrates to, -1 if @p moves from @cpu or @p == NULL
- * @boost: 1 to enable boosting, otherwise 0
- *
- * The unit of the return value must be the same as the one of CPU capacity
- * so that CPU utilization can be compared with CPU capacity.
- *
- * CPU utilization is the sum of running time of runnable tasks plus the
- * recent utilization of currently non-runnable tasks on that CPU.
- * It represents the amount of CPU capacity currently used by CFS tasks in
- * the range [0..max CPU capacity] with max CPU capacity being the CPU
- * capacity at f_max.
- *
- * The estimated CPU utilization is defined as the maximum between CPU
- * utilization and sum of the estimated utilization of the currently
- * runnable tasks on that CPU. It preserves a utilization "snapshot" of
- * previously-executed tasks, which helps better deduce how busy a CPU will
- * be when a long-sleeping task wakes up. The contribution to CPU utilization
- * of such a task would be significantly decayed at this point of time.
- *
- * Boosted CPU utilization is defined as max(CPU runnable, CPU utilization).
- * CPU contention for CFS tasks can be detected by CPU runnable > CPU
- * utilization. Boosting is implemented in cpu_util() so that internal
- * users (e.g. EAS) can use it next to external users (e.g. schedutil),
- * latter via cpu_util_cfs_boost().
- *
- * CPU utilization can be higher than the current CPU capacity
- * (f_curr/f_max * max CPU capacity) or even the max CPU capacity because
- * of rounding errors as well as task migrations or wakeups of new tasks.
- * CPU utilization has to be capped to fit into the [0..max CPU capacity]
- * range. Otherwise a group of CPUs (CPU0 util = 121% + CPU1 util = 80%)
- * could be seen as over-utilized even though CPU1 has 20% of spare CPU
- * capacity. CPU utilization is allowed to overshoot current CPU capacity
- * though since this is useful for predicting the CPU capacity required
- * after task migrations (scheduler-driven DVFS).
- *
- * Return: (Boosted) (estimated) utilization for the specified CPU.
- */
-static unsigned long
-cpu_util(int cpu, struct task_struct *p, int dst_cpu, int boost)
-{
- struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
- unsigned long util = READ_ONCE(cfs_rq->avg.util_avg);
- unsigned long runnable;
-
- if (boost) {
- runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
- util = max(util, runnable);
- }
-
- /*
- * If @dst_cpu is -1 or @p migrates from @cpu to @dst_cpu remove its
- * contribution. If @p migrates from another CPU to @cpu add its
- * contribution. In all the other cases @cpu is not impacted by the
- * migration so its util_avg is already correct.
- */
- if (p && task_cpu(p) == cpu && dst_cpu != cpu)
- lsub_positive(&util, task_util(p));
- else if (p && task_cpu(p) != cpu && dst_cpu == cpu)
- util += task_util(p);
-
- if (sched_feat(UTIL_EST)) {
- unsigned long util_est;
-
- util_est = READ_ONCE(cfs_rq->avg.util_est);
-
- /*
- * During wake-up @p isn't enqueued yet and doesn't contribute
- * to any cpu_rq(cpu)->cfs.avg.util_est.
- * If @dst_cpu == @cpu add it to "simulate" cpu_util after @p
- * has been enqueued.
- *
- * During exec (@dst_cpu = -1) @p is enqueued and does
- * contribute to cpu_rq(cpu)->cfs.util_est.
- * Remove it to "simulate" cpu_util without @p's contribution.
- *
- * Despite the task_on_rq_queued(@p) check there is still a
- * small window for a possible race when an exec
- * select_task_rq_fair() races with LB's detach_task().
- *
- * detach_task()
- * deactivate_task()
- * p->on_rq = TASK_ON_RQ_MIGRATING;
- * -------------------------------- A
- * dequeue_task() \
- * dequeue_task_fair() + Race Time
- * util_est_dequeue() /
- * -------------------------------- B
- *
- * The additional check "current == p" is required to further
- * reduce the race window.
- */
- if (dst_cpu == cpu)
- util_est += _task_util_est(p);
- else if (p && unlikely(task_on_rq_queued(p) || current == p))
- lsub_positive(&util_est, _task_util_est(p));
-
- util = max(util, util_est);
- }
-
- return min(util, arch_scale_cpu_capacity(cpu));
-}
-
-unsigned long cpu_util_cfs(int cpu)
-{
- return cpu_util(cpu, NULL, -1, 0);
-}
-
-unsigned long cpu_util_cfs_boost(int cpu)
-{
- return cpu_util(cpu, NULL, -1, 1);
-}
-
-/*
- * cpu_util_without: compute cpu utilization without any contributions from *p
- * @cpu: the CPU which utilization is requested
- * @p: the task which utilization should be discounted
- *
- * The utilization of a CPU is defined by the utilization of tasks currently
- * enqueued on that CPU as well as tasks which are currently sleeping after an
- * execution on that CPU.
- *
- * This method returns the utilization of the specified CPU by discounting the
- * utilization of the specified task, whenever the task is currently
- * contributing to the CPU utilization.
- */
-static unsigned long cpu_util_without(int cpu, struct task_struct *p)
-{
- /* Task has no contribution or is new */
- if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
- p = NULL;
-
- return cpu_util(cpu, p, -1, 0);
-}
-
-/*
- * energy_env - Utilization landscape for energy estimation.
- * @task_busy_time: Utilization contribution by the task for which we test the
- * placement. Given by eenv_task_busy_time().
- * @pd_busy_time: Utilization of the whole perf domain without the task
- * contribution. Given by eenv_pd_busy_time().
- * @cpu_cap: Maximum CPU capacity for the perf domain.
- * @pd_cap: Entire perf domain capacity. (pd->nr_cpus * cpu_cap).
- */
-struct energy_env {
- unsigned long task_busy_time;
- unsigned long pd_busy_time;
- unsigned long cpu_cap;
- unsigned long pd_cap;
-};
-
-/*
- * Compute the task busy time for compute_energy(). This time cannot be
- * injected directly into effective_cpu_util() because of the IRQ scaling.
- * The latter only makes sense with the most recent CPUs where the task has
- * run.
- */
-static inline void eenv_task_busy_time(struct energy_env *eenv,
- struct task_struct *p, int prev_cpu)
-{
- unsigned long busy_time, max_cap = arch_scale_cpu_capacity(prev_cpu);
- unsigned long irq = cpu_util_irq(cpu_rq(prev_cpu));
-
- if (unlikely(irq >= max_cap))
- busy_time = max_cap;
- else
- busy_time = scale_irq_capacity(task_util_est(p), irq, max_cap);
-
- eenv->task_busy_time = busy_time;
-}
-
-/*
- * Compute the perf_domain (PD) busy time for compute_energy(). Based on the
- * utilization for each @pd_cpus, it however doesn't take into account
- * clamping since the ratio (utilization / cpu_capacity) is already enough to
- * scale the EM reported power consumption at the (eventually clamped)
- * cpu_capacity.
- *
- * The contribution of the task @p for which we want to estimate the
- * energy cost is removed (by cpu_util()) and must be calculated
- * separately (see eenv_task_busy_time). This ensures:
- *
- * - A stable PD utilization, no matter which CPU of that PD we want to place
- * the task on.
- *
- * - A fair comparison between CPUs as the task contribution (task_util())
- * will always be the same no matter which CPU utilization we rely on
- * (util_avg or util_est).
- *
- * Set @eenv busy time for the PD that spans @pd_cpus. This busy time can't
- * exceed @eenv->pd_cap.
- */
-static inline void eenv_pd_busy_time(struct energy_env *eenv,
- struct cpumask *pd_cpus,
- struct task_struct *p)
-{
- unsigned long busy_time = 0;
- int cpu;
-
- for_each_cpu(cpu, pd_cpus) {
- unsigned long util = cpu_util(cpu, p, -1, 0);
-
- busy_time += effective_cpu_util(cpu, util, NULL, NULL);
- }
-
- eenv->pd_busy_time = min(eenv->pd_cap, busy_time);
-}
-
-/*
- * Compute the maximum utilization for compute_energy() when the task @p
- * is placed on the cpu @dst_cpu.
- *
- * Returns the maximum utilization among @eenv->cpus. This utilization can't
- * exceed @eenv->cpu_cap.
- */
-static inline unsigned long
-eenv_pd_max_util(struct energy_env *eenv, struct cpumask *pd_cpus,
- struct task_struct *p, int dst_cpu)
-{
- unsigned long max_util = 0;
- int cpu;
-
- for_each_cpu(cpu, pd_cpus) {
- struct task_struct *tsk = (cpu == dst_cpu) ? p : NULL;
- unsigned long util = cpu_util(cpu, p, dst_cpu, 1);
- unsigned long eff_util, min, max;
-
- /*
- * Performance domain frequency: utilization clamping
- * must be considered since it affects the selection
- * of the performance domain frequency.
- * NOTE: in case RT tasks are running, by default the
- * FREQUENCY_UTIL's utilization can be max OPP.
- */
- eff_util = effective_cpu_util(cpu, util, &min, &max);
-
- /* Task's uclamp can modify min and max value */
- if (tsk && uclamp_is_used()) {
- min = max(min, uclamp_eff_value(p, UCLAMP_MIN));
-
- /*
- * If there is no active max uclamp constraint,
- * directly use task's one, otherwise keep max.
- */
- if (uclamp_rq_is_idle(cpu_rq(cpu)))
- max = uclamp_eff_value(p, UCLAMP_MAX);
- else
- max = max(max, uclamp_eff_value(p, UCLAMP_MAX));
- }
-
- eff_util = sugov_effective_cpu_perf(cpu, eff_util, min, max);
- max_util = max(max_util, eff_util);
- }
-
- return min(max_util, eenv->cpu_cap);
-}
-
-/*
- * compute_energy(): Use the Energy Model to estimate the energy that @pd would
- * consume for a given utilization landscape @eenv. When @dst_cpu < 0, the task
- * contribution is ignored.
- */
-static inline unsigned long
-compute_energy(struct energy_env *eenv, struct perf_domain *pd,
- struct cpumask *pd_cpus, struct task_struct *p, int dst_cpu)
-{
- unsigned long max_util = eenv_pd_max_util(eenv, pd_cpus, p, dst_cpu);
- unsigned long busy_time = eenv->pd_busy_time;
- unsigned long energy;
-
- if (dst_cpu >= 0)
- busy_time = min(eenv->pd_cap, busy_time + eenv->task_busy_time);
-
- energy = em_cpu_energy(pd->em_pd, max_util, busy_time, eenv->cpu_cap);
-
- trace_sched_compute_energy_tp(p, dst_cpu, energy, max_util, busy_time);
-
- return energy;
-}
-
-/*
- * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
- * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
- * spare capacity in each performance domain and uses it as a potential
- * candidate to execute the task. Then, it uses the Energy Model to figure
- * out which of the CPU candidates is the most energy-efficient.
- *
- * The rationale for this heuristic is as follows. In a performance domain,
- * all the most energy efficient CPU candidates (according to the Energy
- * Model) are those for which we'll request a low frequency. When there are
- * several CPUs for which the frequency request will be the same, we don't
- * have enough data to break the tie between them, because the Energy Model
- * only includes active power costs. With this model, if we assume that
- * frequency requests follow utilization (e.g. using schedutil), the CPU with
- * the maximum spare capacity in a performance domain is guaranteed to be among
- * the best candidates of the performance domain.
- *
- * In practice, it could be preferable from an energy standpoint to pack
- * small tasks on a CPU in order to let other CPUs go in deeper idle states,
- * but that could also hurt our chances to go cluster idle, and we have no
- * ways to tell with the current Energy Model if this is actually a good
- * idea or not. So, find_energy_efficient_cpu() basically favors
- * cluster-packing, and spreading inside a cluster. That should at least be
- * a good thing for latency, and this is consistent with the idea that most
- * of the energy savings of EAS come from the asymmetry of the system, and
- * not so much from breaking the tie between identical CPUs. That's also the
- * reason why EAS is enabled in the topology code only for systems where
- * SD_ASYM_CPUCAPACITY is set.
- *
- * NOTE: Forkees are not accepted in the energy-aware wake-up path because
- * they don't have any useful utilization data yet and it's not possible to
- * forecast their impact on energy consumption. Consequently, they will be
- * placed by sched_balance_find_dst_cpu() on the least loaded CPU, which might turn out
- * to be energy-inefficient in some use-cases. The alternative would be to
- * bias new tasks towards specific types of CPUs first, or to try to infer
- * their util_avg from the parent task, but those heuristics could hurt
- * other use-cases too. So, until someone finds a better way to solve this,
- * let's keep things simple by re-using the existing slow path.
- */
-static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
-{
- struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
- unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
- unsigned long p_util_min = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MIN) : 0;
- unsigned long p_util_max = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MAX) : 1024;
- struct root_domain *rd = this_rq()->rd;
- int cpu, best_energy_cpu, target = -1;
- int prev_fits = -1, best_fits = -1;
- unsigned long best_thermal_cap = 0;
- unsigned long prev_thermal_cap = 0;
- struct sched_domain *sd;
- struct perf_domain *pd;
- struct energy_env eenv;
-
- rcu_read_lock();
- pd = rcu_dereference(rd->pd);
- if (!pd)
- goto unlock;
-
- /*
- * Energy-aware wake-up happens on the lowest sched_domain starting
- * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
- */
- sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
- while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
- sd = sd->parent;
- if (!sd)
- goto unlock;
-
- target = prev_cpu;
-
- sync_entity_load_avg(&p->se);
- if (!task_util_est(p) && p_util_min == 0)
- goto unlock;
-
- eenv_task_busy_time(&eenv, p, prev_cpu);
-
- for (; pd; pd = pd->next) {
- unsigned long util_min = p_util_min, util_max = p_util_max;
- unsigned long cpu_cap, cpu_thermal_cap, util;
- long prev_spare_cap = -1, max_spare_cap = -1;
- unsigned long rq_util_min, rq_util_max;
- unsigned long cur_delta, base_energy;
- int max_spare_cap_cpu = -1;
- int fits, max_fits = -1;
-
- cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
-
- if (cpumask_empty(cpus))
- continue;
-
- /* Account thermal pressure for the energy estimation */
- cpu = cpumask_first(cpus);
- cpu_thermal_cap = arch_scale_cpu_capacity(cpu);
- cpu_thermal_cap -= arch_scale_thermal_pressure(cpu);
-
- eenv.cpu_cap = cpu_thermal_cap;
- eenv.pd_cap = 0;
-
- for_each_cpu(cpu, cpus) {
- struct rq *rq = cpu_rq(cpu);
-
- eenv.pd_cap += cpu_thermal_cap;
-
- if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
- continue;
-
- if (!cpumask_test_cpu(cpu, p->cpus_ptr))
- continue;
-
- util = cpu_util(cpu, p, cpu, 0);
- cpu_cap = capacity_of(cpu);
-
- /*
- * Skip CPUs that cannot satisfy the capacity request.
- * IOW, placing the task there would make the CPU
- * overutilized. Take uclamp into account to see how
- * much capacity we can get out of the CPU; this is
- * aligned with sched_cpu_util().
- */
- if (uclamp_is_used() && !uclamp_rq_is_idle(rq)) {
- /*
- * Open code uclamp_rq_util_with() except for
- * the clamp() part. I.e.: apply max aggregation
- * only. util_fits_cpu() logic requires to
- * operate on non clamped util but must use the
- * max-aggregated uclamp_{min, max}.
- */
- rq_util_min = uclamp_rq_get(rq, UCLAMP_MIN);
- rq_util_max = uclamp_rq_get(rq, UCLAMP_MAX);
-
- util_min = max(rq_util_min, p_util_min);
- util_max = max(rq_util_max, p_util_max);
- }
-
- fits = util_fits_cpu(util, util_min, util_max, cpu);
- if (!fits)
- continue;
-
- lsub_positive(&cpu_cap, util);
-
- if (cpu == prev_cpu) {
- /* Always use prev_cpu as a candidate. */
- prev_spare_cap = cpu_cap;
- prev_fits = fits;
- } else if ((fits > max_fits) ||
- ((fits == max_fits) && ((long)cpu_cap > max_spare_cap))) {
- /*
- * Find the CPU with the maximum spare capacity
- * among the remaining CPUs in the performance
- * domain.
- */
- max_spare_cap = cpu_cap;
- max_spare_cap_cpu = cpu;
- max_fits = fits;
- }
- }
-
- if (max_spare_cap_cpu < 0 && prev_spare_cap < 0)
- continue;
-
- eenv_pd_busy_time(&eenv, cpus, p);
- /* Compute the 'base' energy of the pd, without @p */
- base_energy = compute_energy(&eenv, pd, cpus, p, -1);
-
- /* Evaluate the energy impact of using prev_cpu. */
- if (prev_spare_cap > -1) {
- prev_delta = compute_energy(&eenv, pd, cpus, p,
- prev_cpu);
- /* CPU utilization has changed */
- if (prev_delta < base_energy)
- goto unlock;
- prev_delta -= base_energy;
- prev_thermal_cap = cpu_thermal_cap;
- best_delta = min(best_delta, prev_delta);
- }
-
- /* Evaluate the energy impact of using max_spare_cap_cpu. */
- if (max_spare_cap_cpu >= 0 && max_spare_cap > prev_spare_cap) {
- /* Current best energy cpu fits better */
- if (max_fits < best_fits)
- continue;
-
- /*
- * Both don't fit performance hint (i.e. uclamp_min)
- * but best energy cpu has better capacity.
- */
- if ((max_fits < 0) &&
- (cpu_thermal_cap <= best_thermal_cap))
- continue;
-
- cur_delta = compute_energy(&eenv, pd, cpus, p,
- max_spare_cap_cpu);
- /* CPU utilization has changed */
- if (cur_delta < base_energy)
- goto unlock;
- cur_delta -= base_energy;
-
- /*
- * Both fit for the task but best energy cpu has lower
- * energy impact.
- */
- if ((max_fits > 0) && (best_fits > 0) &&
- (cur_delta >= best_delta))
- continue;
-
- best_delta = cur_delta;
- best_energy_cpu = max_spare_cap_cpu;
- best_fits = max_fits;
- best_thermal_cap = cpu_thermal_cap;
- }
- }
- rcu_read_unlock();
-
- if ((best_fits > prev_fits) ||
- ((best_fits > 0) && (best_delta < prev_delta)) ||
- ((best_fits < 0) && (best_thermal_cap > prev_thermal_cap)))
- target = best_energy_cpu;
-
- return target;
-
-unlock:
- rcu_read_unlock();
-
- return target;
-}
-
-/*
- * select_task_rq_fair: Select target runqueue for the waking task in domains
- * that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE,
- * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
- *
- * Balances load by selecting the idlest CPU in the idlest group, or under
- * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
- *
- * Returns the target CPU number.
- */
-static int
-select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
-{
- int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
- struct sched_domain *tmp, *sd = NULL;
- int cpu = smp_processor_id();
- int new_cpu = prev_cpu;
- int want_affine = 0;
- /* SD_flags and WF_flags share the first nibble */
- int sd_flag = wake_flags & 0xF;
-
- /*
- * required for stable ->cpus_allowed
- */
- lockdep_assert_held(&p->pi_lock);
- if (wake_flags & WF_TTWU) {
- record_wakee(p);
-
- if ((wake_flags & WF_CURRENT_CPU) &&
- cpumask_test_cpu(cpu, p->cpus_ptr))
- return cpu;
-
- if (!is_rd_overutilized(this_rq()->rd)) {
- new_cpu = find_energy_efficient_cpu(p, prev_cpu);
- if (new_cpu >= 0)
- return new_cpu;
- new_cpu = prev_cpu;
- }
-
- want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
- }
-
- rcu_read_lock();
- for_each_domain(cpu, tmp) {
- /*
- * If both 'cpu' and 'prev_cpu' are part of this domain,
- * cpu is a valid SD_WAKE_AFFINE target.
- */
- if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
- cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
- if (cpu != prev_cpu)
- new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
-
- sd = NULL; /* Prefer wake_affine over balance flags */
- break;
- }
-
- /*
- * Usually only true for WF_EXEC and WF_FORK, as sched_domains
- * usually do not have SD_BALANCE_WAKE set. That means wakeup
- * will usually go to the fast path.
- */
- if (tmp->flags & sd_flag)
- sd = tmp;
- else if (!want_affine)
- break;
- }
-
- if (unlikely(sd)) {
- /* Slow path */
- new_cpu = sched_balance_find_dst_cpu(sd, p, cpu, prev_cpu, sd_flag);
- } else if (wake_flags & WF_TTWU) { /* XXX always ? */
- /* Fast path */
- new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
- }
- rcu_read_unlock();
-
- return new_cpu;
-}
-
-/*
- * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
- * cfs_rq_of(p) references at time of call are still valid and identify the
- * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
- */
-static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
-{
- struct sched_entity *se = &p->se;
-
- if (!task_on_rq_migrating(p)) {
- remove_entity_load_avg(se);
-
- /*
- * Here, the task's PELT values have been updated according to
- * the current rq's clock. But if that clock hasn't been
- * updated in a while, a substantial idle time will be missed,
- * leading to an inflation after wake-up on the new rq.
- *
- * Estimate the missing time from the cfs_rq last_update_time
- * and update sched_avg to improve the PELT continuity after
- * migration.
- */
- migrate_se_pelt_lag(se);
- }
-
- /* Tell new CPU we are migrated */
- se->avg.last_update_time = 0;
-
- update_scan_period(p, new_cpu);
-}
-
-static void task_dead_fair(struct task_struct *p)
-{
- remove_entity_load_avg(&p->se);
-}
-
-/*
- * Set the max capacity the task is allowed to run at for misfit detection.
- */
-static void set_task_max_allowed_capacity(struct task_struct *p)
-{
- struct asym_cap_data *entry;
-
- if (!sched_asym_cpucap_active())
- return;
-
- rcu_read_lock();
- list_for_each_entry_rcu(entry, &asym_cap_list, link) {
- cpumask_t *cpumask;
-
- cpumask = cpu_capacity_span(entry);
- if (!cpumask_intersects(p->cpus_ptr, cpumask))
- continue;
-
- p->max_allowed_capacity = entry->capacity;
- break;
- }
- rcu_read_unlock();
-}
-
-static void set_cpus_allowed_fair(struct task_struct *p, struct affinity_context *ctx)
-{
- set_cpus_allowed_common(p, ctx);
- set_task_max_allowed_capacity(p);
-}
-
-static int
-balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
-{
- if (rq->nr_running)
- return 1;
-
- return sched_balance_newidle(rq, rf) != 0;
-}
-#else
-static inline void set_task_max_allowed_capacity(struct task_struct *p) {}
-#endif /* CONFIG_SMP */
-
-static void set_next_buddy(struct sched_entity *se)
-{
- for_each_sched_entity(se) {
- if (SCHED_WARN_ON(!se->on_rq))
- return;
- if (se_is_idle(se))
- return;
- cfs_rq_of(se)->next = se;
- }
-}
-
-/*
- * Preempt the current task with a newly woken task if needed:
- */
-static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int wake_flags)
-{
- struct task_struct *curr = rq->curr;
- struct sched_entity *se = &curr->se, *pse = &p->se;
- struct cfs_rq *cfs_rq = task_cfs_rq(curr);
- int cse_is_idle, pse_is_idle;
-
- if (unlikely(se == pse))
- return;
-
- /*
- * This is possible from callers such as attach_tasks(), in which we
- * unconditionally wakeup_preempt() after an enqueue (which may have
- * lead to a throttle). This both saves work and prevents false
- * next-buddy nomination below.
- */
- if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
- return;
-
- if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) {
- set_next_buddy(pse);
- }
-
- /*
- * We can come here with TIF_NEED_RESCHED already set from new task
- * wake up path.
- *
- * Note: this also catches the edge-case of curr being in a throttled
- * group (e.g. via set_curr_task), since update_curr() (in the
- * enqueue of curr) will have resulted in resched being set. This
- * prevents us from potentially nominating it as a false LAST_BUDDY
- * below.
- */
- if (test_tsk_need_resched(curr))
- return;
-
- /* Idle tasks are by definition preempted by non-idle tasks. */
- if (unlikely(task_has_idle_policy(curr)) &&
- likely(!task_has_idle_policy(p)))
- goto preempt;
-
- /*
- * Batch and idle tasks do not preempt non-idle tasks (their preemption
- * is driven by the tick):
- */
- if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
- return;
-
- find_matching_se(&se, &pse);
- WARN_ON_ONCE(!pse);
-
- cse_is_idle = se_is_idle(se);
- pse_is_idle = se_is_idle(pse);
-
- /*
- * Preempt an idle group in favor of a non-idle group (and don't preempt
- * in the inverse case).
- */
- if (cse_is_idle && !pse_is_idle)
- goto preempt;
- if (cse_is_idle != pse_is_idle)
- return;
-
- cfs_rq = cfs_rq_of(se);
- update_curr(cfs_rq);
-
- /*
- * XXX pick_eevdf(cfs_rq) != se ?
- */
- if (pick_eevdf(cfs_rq) == pse)
- goto preempt;
-
- return;
-
-preempt:
- resched_curr(rq);
-}
-
-#ifdef CONFIG_SMP
-static struct task_struct *pick_task_fair(struct rq *rq)
-{
- struct sched_entity *se;
- struct cfs_rq *cfs_rq;
-
-again:
- cfs_rq = &rq->cfs;
- if (!cfs_rq->nr_running)
- return NULL;
-
- do {
- struct sched_entity *curr = cfs_rq->curr;
-
- /* When we pick for a remote RQ, we'll not have done put_prev_entity() */
- if (curr) {
- if (curr->on_rq)
- update_curr(cfs_rq);
- else
- curr = NULL;
-
- if (unlikely(check_cfs_rq_runtime(cfs_rq)))
- goto again;
- }
-
- se = pick_next_entity(cfs_rq);
- cfs_rq = group_cfs_rq(se);
- } while (cfs_rq);
-
- return task_of(se);
-}
-#endif
-
-struct task_struct *
-pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
-{
- struct cfs_rq *cfs_rq = &rq->cfs;
- struct sched_entity *se;
- struct task_struct *p;
- int new_tasks;
-
-again:
- if (!sched_fair_runnable(rq))
- goto idle;
-
-#ifdef CONFIG_FAIR_GROUP_SCHED
- if (!prev || prev->sched_class != &fair_sched_class)
- goto simple;
-
- /*
- * Because of the set_next_buddy() in dequeue_task_fair() it is rather
- * likely that a next task is from the same cgroup as the current.
- *
- * Therefore attempt to avoid putting and setting the entire cgroup
- * hierarchy, only change the part that actually changes.
- */
-
- do {
- struct sched_entity *curr = cfs_rq->curr;
-
- /*
- * Since we got here without doing put_prev_entity() we also
- * have to consider cfs_rq->curr. If it is still a runnable
- * entity, update_curr() will update its vruntime, otherwise
- * forget we've ever seen it.
- */
- if (curr) {
- if (curr->on_rq)
- update_curr(cfs_rq);
- else
- curr = NULL;
-
- /*
- * This call to check_cfs_rq_runtime() will do the
- * throttle and dequeue its entity in the parent(s).
- * Therefore the nr_running test will indeed
- * be correct.
- */
- if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
- cfs_rq = &rq->cfs;
-
- if (!cfs_rq->nr_running)
- goto idle;
-
- goto simple;
- }
- }
-
- se = pick_next_entity(cfs_rq);
- cfs_rq = group_cfs_rq(se);
- } while (cfs_rq);
-
- p = task_of(se);
-
- /*
- * Since we haven't yet done put_prev_entity and if the selected task
- * is a different task than we started out with, try and touch the
- * least amount of cfs_rqs.
- */
- if (prev != p) {
- struct sched_entity *pse = &prev->se;
-
- while (!(cfs_rq = is_same_group(se, pse))) {
- int se_depth = se->depth;
- int pse_depth = pse->depth;
-
- if (se_depth <= pse_depth) {
- put_prev_entity(cfs_rq_of(pse), pse);
- pse = parent_entity(pse);
- }
- if (se_depth >= pse_depth) {
- set_next_entity(cfs_rq_of(se), se);
- se = parent_entity(se);
- }
- }
-
- put_prev_entity(cfs_rq, pse);
- set_next_entity(cfs_rq, se);
- }
-
- goto done;
-simple:
-#endif
- if (prev)
- put_prev_task(rq, prev);
-
- do {
- se = pick_next_entity(cfs_rq);
- set_next_entity(cfs_rq, se);
- cfs_rq = group_cfs_rq(se);
- } while (cfs_rq);
-
- p = task_of(se);
-
-done: __maybe_unused;
-#ifdef CONFIG_SMP
- /*
- * Move the next running task to the front of
- * the list, so our cfs_tasks list becomes MRU
- * one.
- */
- list_move(&p->se.group_node, &rq->cfs_tasks);
-#endif
-
- if (hrtick_enabled_fair(rq))
- hrtick_start_fair(rq, p);
-
- update_misfit_status(p, rq);
- sched_fair_update_stop_tick(rq, p);
-
- return p;
-
-idle:
- if (!rf)
- return NULL;
-
- new_tasks = sched_balance_newidle(rq, rf);
-
- /*
- * Because sched_balance_newidle() releases (and re-acquires) rq->lock, it is
- * possible for any higher priority task to appear. In that case we
- * must re-start the pick_next_entity() loop.
- */
- if (new_tasks < 0)
- return RETRY_TASK;
-
- if (new_tasks > 0)
- goto again;
-
- /*
- * rq is about to be idle, check if we need to update the
- * lost_idle_time of clock_pelt
- */
- update_idle_rq_clock_pelt(rq);
-
- return NULL;
-}
-
-static struct task_struct *__pick_next_task_fair(struct rq *rq)
-{
- return pick_next_task_fair(rq, NULL, NULL);
-}
-
-/*
- * Account for a descheduled task:
- */
-static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
-{
- struct sched_entity *se = &prev->se;
- struct cfs_rq *cfs_rq;
-
- for_each_sched_entity(se) {
- cfs_rq = cfs_rq_of(se);
- put_prev_entity(cfs_rq, se);
- }
-}
-
-/*
- * sched_yield() is very simple
- */
-static void yield_task_fair(struct rq *rq)
-{
- struct task_struct *curr = rq->curr;
- struct cfs_rq *cfs_rq = task_cfs_rq(curr);
- struct sched_entity *se = &curr->se;
-
- /*
- * Are we the only task in the tree?
- */
- if (unlikely(rq->nr_running == 1))
- return;
-
- clear_buddies(cfs_rq, se);
-
- update_rq_clock(rq);
- /*
- * Update run-time statistics of the 'current'.
- */
- update_curr(cfs_rq);
- /*
- * Tell update_rq_clock() that we've just updated,
- * so we don't do microscopic update in schedule()
- * and double the fastpath cost.
- */
- rq_clock_skip_update(rq);
-
- se->deadline += calc_delta_fair(se->slice, se);
-}
-
-static bool yield_to_task_fair(struct rq *rq, struct task_struct *p)
-{
- struct sched_entity *se = &p->se;
-
- /* throttled hierarchies are not runnable */
- if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
- return false;
-
- /* Tell the scheduler that we'd really like se to run next. */
- set_next_buddy(se);
-
- yield_task_fair(rq);
-
- return true;
-}
-
-#ifdef CONFIG_SMP
-/**************************************************
- * Fair scheduling class load-balancing methods.
- *
- * BASICS
- *
- * The purpose of load-balancing is to achieve the same basic fairness the
- * per-CPU scheduler provides, namely provide a proportional amount of compute
- * time to each task. This is expressed in the following equation:
- *
- * W_i,n/P_i == W_j,n/P_j for all i,j (1)
- *
- * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
- * W_i,0 is defined as:
- *
- * W_i,0 = \Sum_j w_i,j (2)
- *
- * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
- * is derived from the nice value as per sched_prio_to_weight[].
- *
- * The weight average is an exponential decay average of the instantaneous
- * weight:
- *
- * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
- *
- * C_i is the compute capacity of CPU i, typically it is the
- * fraction of 'recent' time available for SCHED_OTHER task execution. But it
- * can also include other factors [XXX].
- *
- * To achieve this balance we define a measure of imbalance which follows
- * directly from (1):
- *
- * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
- *
- * We them move tasks around to minimize the imbalance. In the continuous
- * function space it is obvious this converges, in the discrete case we get
- * a few fun cases generally called infeasible weight scenarios.
- *
- * [XXX expand on:
- * - infeasible weights;
- * - local vs global optima in the discrete case. ]
- *
- *
- * SCHED DOMAINS
- *
- * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
- * for all i,j solution, we create a tree of CPUs that follows the hardware
- * topology where each level pairs two lower groups (or better). This results
- * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
- * tree to only the first of the previous level and we decrease the frequency
- * of load-balance at each level inv. proportional to the number of CPUs in
- * the groups.
- *
- * This yields:
- *
- * log_2 n 1 n
- * \Sum { --- * --- * 2^i } = O(n) (5)
- * i = 0 2^i 2^i
- * `- size of each group
- * | | `- number of CPUs doing load-balance
- * | `- freq
- * `- sum over all levels
- *
- * Coupled with a limit on how many tasks we can migrate every balance pass,
- * this makes (5) the runtime complexity of the balancer.
- *
- * An important property here is that each CPU is still (indirectly) connected
- * to every other CPU in at most O(log n) steps:
- *
- * The adjacency matrix of the resulting graph is given by:
- *
- * log_2 n
- * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
- * k = 0
- *
- * And you'll find that:
- *
- * A^(log_2 n)_i,j != 0 for all i,j (7)
- *
- * Showing there's indeed a path between every CPU in at most O(log n) steps.
- * The task movement gives a factor of O(m), giving a convergence complexity
- * of:
- *
- * O(nm log n), n := nr_cpus, m := nr_tasks (8)
- *
- *
- * WORK CONSERVING
- *
- * In order to avoid CPUs going idle while there's still work to do, new idle
- * balancing is more aggressive and has the newly idle CPU iterate up the domain
- * tree itself instead of relying on other CPUs to bring it work.
- *
- * This adds some complexity to both (5) and (8) but it reduces the total idle
- * time.
- *
- * [XXX more?]
- *
- *
- * CGROUPS
- *
- * Cgroups make a horror show out of (2), instead of a simple sum we get:
- *
- * s_k,i
- * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
- * S_k
- *
- * Where
- *
- * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
- *
- * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
- *
- * The big problem is S_k, its a global sum needed to compute a local (W_i)
- * property.
- *
- * [XXX write more on how we solve this.. _after_ merging pjt's patches that
- * rewrite all of this once again.]
- */
-
-static unsigned long __read_mostly max_load_balance_interval = HZ/10;
-
-enum fbq_type { regular, remote, all };
-
-/*
- * 'group_type' describes the group of CPUs at the moment of load balancing.
- *
- * The enum is ordered by pulling priority, with the group with lowest priority
- * first so the group_type can simply be compared when selecting the busiest
- * group. See update_sd_pick_busiest().
- */
-enum group_type {
- /* The group has spare capacity that can be used to run more tasks. */
- group_has_spare = 0,
- /*
- * The group is fully used and the tasks don't compete for more CPU
- * cycles. Nevertheless, some tasks might wait before running.
- */
- group_fully_busy,
- /*
- * One task doesn't fit with CPU's capacity and must be migrated to a
- * more powerful CPU.
- */
- group_misfit_task,
- /*
- * Balance SMT group that's fully busy. Can benefit from migration
- * a task on SMT with busy sibling to another CPU on idle core.
- */
- group_smt_balance,
- /*
- * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
- * and the task should be migrated to it instead of running on the
- * current CPU.
- */
- group_asym_packing,
- /*
- * The tasks' affinity constraints previously prevented the scheduler
- * from balancing the load across the system.
- */
- group_imbalanced,
- /*
- * The CPU is overloaded and can't provide expected CPU cycles to all
- * tasks.
- */
- group_overloaded
-};
-
-enum migration_type {
- migrate_load = 0,
- migrate_util,
- migrate_task,
- migrate_misfit
-};
-
-#define LBF_ALL_PINNED 0x01
-#define LBF_NEED_BREAK 0x02
-#define LBF_DST_PINNED 0x04
-#define LBF_SOME_PINNED 0x08
-#define LBF_ACTIVE_LB 0x10
-
-struct lb_env {
- struct sched_domain *sd;
-
- struct rq *src_rq;
- int src_cpu;
-
- int dst_cpu;
- struct rq *dst_rq;
-
- struct cpumask *dst_grpmask;
- int new_dst_cpu;
- enum cpu_idle_type idle;
- long imbalance;
- /* The set of CPUs under consideration for load-balancing */
- struct cpumask *cpus;
-
- unsigned int flags;
-
- unsigned int loop;
- unsigned int loop_break;
- unsigned int loop_max;
-
- enum fbq_type fbq_type;
- enum migration_type migration_type;
- struct list_head tasks;
-};
-
-/*
- * Is this task likely cache-hot:
- */
-static int task_hot(struct task_struct *p, struct lb_env *env)
-{
- s64 delta;
-
- lockdep_assert_rq_held(env->src_rq);
-
- if (p->sched_class != &fair_sched_class)
- return 0;
-
- if (unlikely(task_has_idle_policy(p)))
- return 0;
-
- /* SMT siblings share cache */
- if (env->sd->flags & SD_SHARE_CPUCAPACITY)
- return 0;
-
- /*
- * Buddy candidates are cache hot:
- */
- if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
- (&p->se == cfs_rq_of(&p->se)->next))
- return 1;
-
- if (sysctl_sched_migration_cost == -1)
- return 1;
-
- /*
- * Don't migrate task if the task's cookie does not match
- * with the destination CPU's core cookie.
- */
- if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p))
- return 1;
+ if (!remaining) {
+ throttled = true;
+ break;
+ }
- if (sysctl_sched_migration_cost == 0)
- return 0;
+ rq_lock_irqsave(rq, &rf);
+ if (!cfs_rq_throttled(cfs_rq))
+ goto next;
- delta = rq_clock_task(env->src_rq) - p->se.exec_start;
+ /* Already queued for async unthrottle */
+ if (!list_empty(&cfs_rq->throttled_csd_list))
+ goto next;
- return delta < (s64)sysctl_sched_migration_cost;
-}
+ /* By the above checks, this should never be true */
+ SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
-#ifdef CONFIG_NUMA_BALANCING
-/*
- * Returns 1, if task migration degrades locality
- * Returns 0, if task migration improves locality i.e migration preferred.
- * Returns -1, if task migration is not affected by locality.
- */
-static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
-{
- struct numa_group *numa_group = rcu_dereference(p->numa_group);
- unsigned long src_weight, dst_weight;
- int src_nid, dst_nid, dist;
+ raw_spin_lock(&cfs_b->lock);
+ runtime = -cfs_rq->runtime_remaining + 1;
+ if (runtime > cfs_b->runtime)
+ runtime = cfs_b->runtime;
+ cfs_b->runtime -= runtime;
+ remaining = cfs_b->runtime;
+ raw_spin_unlock(&cfs_b->lock);
- if (!static_branch_likely(&sched_numa_balancing))
- return -1;
+ cfs_rq->runtime_remaining += runtime;
- if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
- return -1;
+ /* we check whether we're throttled above */
+ if (cfs_rq->runtime_remaining > 0) {
+ if (cpu_of(rq) != this_cpu) {
+ unthrottle_cfs_rq_async(cfs_rq);
+ } else {
+ /*
+ * We currently only expect to be unthrottling
+ * a single cfs_rq locally.
+ */
+ SCHED_WARN_ON(!list_empty(&local_unthrottle));
+ list_add_tail(&cfs_rq->throttled_csd_list,
+ &local_unthrottle);
+ }
+ } else {
+ throttled = true;
+ }
- src_nid = cpu_to_node(env->src_cpu);
- dst_nid = cpu_to_node(env->dst_cpu);
+next:
+ rq_unlock_irqrestore(rq, &rf);
+ }
- if (src_nid == dst_nid)
- return -1;
+ list_for_each_entry_safe(cfs_rq, tmp, &local_unthrottle,
+ throttled_csd_list) {
+ struct rq *rq = rq_of(cfs_rq);
- /* Migrating away from the preferred node is always bad. */
- if (src_nid == p->numa_preferred_nid) {
- if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
- return 1;
- else
- return -1;
- }
+ rq_lock_irqsave(rq, &rf);
- /* Encourage migration to the preferred node. */
- if (dst_nid == p->numa_preferred_nid)
- return 0;
+ list_del_init(&cfs_rq->throttled_csd_list);
- /* Leaving a core idle is often worse than degrading locality. */
- if (env->idle == CPU_IDLE)
- return -1;
+ if (cfs_rq_throttled(cfs_rq))
+ unthrottle_cfs_rq(cfs_rq);
- dist = node_distance(src_nid, dst_nid);
- if (numa_group) {
- src_weight = group_weight(p, src_nid, dist);
- dst_weight = group_weight(p, dst_nid, dist);
- } else {
- src_weight = task_weight(p, src_nid, dist);
- dst_weight = task_weight(p, dst_nid, dist);
+ rq_unlock_irqrestore(rq, &rf);
}
+ SCHED_WARN_ON(!list_empty(&local_unthrottle));
- return dst_weight < src_weight;
-}
+ rcu_read_unlock();
-#else
-static inline int migrate_degrades_locality(struct task_struct *p,
- struct lb_env *env)
-{
- return -1;
+ return throttled;
}
-#endif
/*
- * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
+ * Responsible for refilling a task_group's bandwidth and unthrottling its
+ * cfs_rqs as appropriate. If there has been no activity within the last
+ * period the timer is deactivated until scheduling resumes; cfs_b->idle is
+ * used to track this state.
*/
-static
-int can_migrate_task(struct task_struct *p, struct lb_env *env)
+static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
{
- int tsk_cache_hot;
-
- lockdep_assert_rq_held(env->src_rq);
-
- /*
- * We do not migrate tasks that are:
- * 1) throttled_lb_pair, or
- * 2) cannot be migrated to this CPU due to cpus_ptr, or
- * 3) running (obviously), or
- * 4) are cache-hot on their current CPU.
- */
- if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
- return 0;
-
- /* Disregard percpu kthreads; they are where they need to be. */
- if (kthread_is_per_cpu(p))
- return 0;
+ int throttled;
- if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
- int cpu;
+ /* no need to continue the timer with no bandwidth constraint */
+ if (cfs_b->quota == RUNTIME_INF)
+ goto out_deactivate;
- schedstat_inc(p->stats.nr_failed_migrations_affine);
+ throttled = !list_empty(&cfs_b->throttled_cfs_rq);
+ cfs_b->nr_periods += overrun;
- env->flags |= LBF_SOME_PINNED;
+ /* Refill extra burst quota even if cfs_b->idle */
+ __refill_cfs_bandwidth_runtime(cfs_b);
- /*
- * Remember if this task can be migrated to any other CPU in
- * our sched_group. We may want to revisit it if we couldn't
- * meet load balance goals by pulling other tasks on src_cpu.
- *
- * Avoid computing new_dst_cpu
- * - for NEWLY_IDLE
- * - if we have already computed one in current iteration
- * - if it's an active balance
- */
- if (env->idle == CPU_NEWLY_IDLE ||
- env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB))
- return 0;
-
- /* Prevent to re-select dst_cpu via env's CPUs: */
- for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
- if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
- env->flags |= LBF_DST_PINNED;
- env->new_dst_cpu = cpu;
- break;
- }
- }
+ /*
+ * idle depends on !throttled (for the case of a large deficit), and if
+ * we're going inactive then everything else can be deferred
+ */
+ if (cfs_b->idle && !throttled)
+ goto out_deactivate;
+ if (!throttled) {
+ /* mark as potentially idle for the upcoming period */
+ cfs_b->idle = 1;
return 0;
}
- /* Record that we found at least one task that could run on dst_cpu */
- env->flags &= ~LBF_ALL_PINNED;
+ /* account preceding periods in which throttling occurred */
+ cfs_b->nr_throttled += overrun;
- if (task_on_cpu(env->src_rq, p)) {
- schedstat_inc(p->stats.nr_failed_migrations_running);
- return 0;
+ /*
+ * This check is repeated as we release cfs_b->lock while we unthrottle.
+ */
+ while (throttled && cfs_b->runtime > 0) {
+ raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
+ /* we can't nest cfs_b->lock while distributing bandwidth */
+ throttled = distribute_cfs_runtime(cfs_b);
+ raw_spin_lock_irqsave(&cfs_b->lock, flags);
}
/*
- * Aggressive migration if:
- * 1) active balance
- * 2) destination numa is preferred
- * 3) task is cache cold, or
- * 4) too many balance attempts have failed.
+ * While we are ensured activity in the period following an
+ * unthrottle, this also covers the case in which the new bandwidth is
+ * insufficient to cover the existing bandwidth deficit. (Forcing the
+ * timer to remain active while there are any throttled entities.)
*/
- if (env->flags & LBF_ACTIVE_LB)
- return 1;
-
- tsk_cache_hot = migrate_degrades_locality(p, env);
- if (tsk_cache_hot == -1)
- tsk_cache_hot = task_hot(p, env);
-
- if (tsk_cache_hot <= 0 ||
- env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
- if (tsk_cache_hot == 1) {
- schedstat_inc(env->sd->lb_hot_gained[env->idle]);
- schedstat_inc(p->stats.nr_forced_migrations);
- }
- return 1;
- }
+ cfs_b->idle = 0;
- schedstat_inc(p->stats.nr_failed_migrations_hot);
return 0;
-}
-
-/*
- * detach_task() -- detach the task for the migration specified in env
- */
-static void detach_task(struct task_struct *p, struct lb_env *env)
-{
- lockdep_assert_rq_held(env->src_rq);
- deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
- set_task_cpu(p, env->dst_cpu);
+out_deactivate:
+ return 1;
}
+/* a cfs_rq won't donate quota below this amount */
+static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
+/* minimum remaining period time to redistribute slack quota */
+static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
+/* how long we wait to gather additional slack before distributing */
+static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
+
/*
- * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
- * part of active balancing operations within "domain".
+ * Are we near the end of the current quota period?
*
- * Returns a task if successful and NULL otherwise.
+ * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
+ * hrtimer base being cleared by hrtimer_start. In the case of
+ * migrate_hrtimers, base is never cleared, so we are fine.
*/
-static struct task_struct *detach_one_task(struct lb_env *env)
+static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
- struct task_struct *p;
-
- lockdep_assert_rq_held(env->src_rq);
+ struct hrtimer *refresh_timer = &cfs_b->period_timer;
+ s64 remaining;
- list_for_each_entry_reverse(p,
- &env->src_rq->cfs_tasks, se.group_node) {
- if (!can_migrate_task(p, env))
- continue;
+ /* if the call-back is running a quota refresh is already occurring */
+ if (hrtimer_callback_running(refresh_timer))
+ return 1;
- detach_task(p, env);
+ /* is a quota refresh about to occur? */
+ remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
+ if (remaining < (s64)min_expire)
+ return 1;
- /*
- * Right now, this is only the second place where
- * lb_gained[env->idle] is updated (other is detach_tasks)
- * so we can safely collect stats here rather than
- * inside detach_tasks().
- */
- schedstat_inc(env->sd->lb_gained[env->idle]);
- return p;
- }
- return NULL;
+ return 0;
}
-/*
- * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
- * busiest_rq, as part of a balancing operation within domain "sd".
- *
- * Returns number of detached tasks if successful and 0 otherwise.
- */
-static int detach_tasks(struct lb_env *env)
+static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
{
- struct list_head *tasks = &env->src_rq->cfs_tasks;
- unsigned long util, load;
- struct task_struct *p;
- int detached = 0;
-
- lockdep_assert_rq_held(env->src_rq);
-
- /*
- * Source run queue has been emptied by another CPU, clear
- * LBF_ALL_PINNED flag as we will not test any task.
- */
- if (env->src_rq->nr_running <= 1) {
- env->flags &= ~LBF_ALL_PINNED;
- return 0;
- }
-
- if (env->imbalance <= 0)
- return 0;
-
- while (!list_empty(tasks)) {
- /*
- * We don't want to steal all, otherwise we may be treated likewise,
- * which could at worst lead to a livelock crash.
- */
- if (env->idle && env->src_rq->nr_running <= 1)
- break;
-
- env->loop++;
- /*
- * We've more or less seen every task there is, call it quits
- * unless we haven't found any movable task yet.
- */
- if (env->loop > env->loop_max &&
- !(env->flags & LBF_ALL_PINNED))
- break;
-
- /* take a breather every nr_migrate tasks */
- if (env->loop > env->loop_break) {
- env->loop_break += SCHED_NR_MIGRATE_BREAK;
- env->flags |= LBF_NEED_BREAK;
- break;
- }
-
- p = list_last_entry(tasks, struct task_struct, se.group_node);
-
- if (!can_migrate_task(p, env))
- goto next;
-
- switch (env->migration_type) {
- case migrate_load:
- /*
- * Depending of the number of CPUs and tasks and the
- * cgroup hierarchy, task_h_load() can return a null
- * value. Make sure that env->imbalance decreases
- * otherwise detach_tasks() will stop only after
- * detaching up to loop_max tasks.
- */
- load = max_t(unsigned long, task_h_load(p), 1);
-
- if (sched_feat(LB_MIN) &&
- load < 16 && !env->sd->nr_balance_failed)
- goto next;
-
- /*
- * Make sure that we don't migrate too much load.
- * Nevertheless, let relax the constraint if
- * scheduler fails to find a good waiting task to
- * migrate.
- */
- if (shr_bound(load, env->sd->nr_balance_failed) > env->imbalance)
- goto next;
-
- env->imbalance -= load;
- break;
-
- case migrate_util:
- util = task_util_est(p);
-
- if (shr_bound(util, env->sd->nr_balance_failed) > env->imbalance)
- goto next;
-
- env->imbalance -= util;
- break;
-
- case migrate_task:
- env->imbalance--;
- break;
+ u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
- case migrate_misfit:
- /* This is not a misfit task */
- if (task_fits_cpu(p, env->src_cpu))
- goto next;
+ /* if there's a quota refresh soon don't bother with slack */
+ if (runtime_refresh_within(cfs_b, min_left))
+ return;
- env->imbalance = 0;
- break;
- }
+ /* don't push forwards an existing deferred unthrottle */
+ if (cfs_b->slack_started)
+ return;
+ cfs_b->slack_started = true;
- detach_task(p, env);
- list_add(&p->se.group_node, &env->tasks);
+ hrtimer_start(&cfs_b->slack_timer,
+ ns_to_ktime(cfs_bandwidth_slack_period),
+ HRTIMER_MODE_REL);
+}
- detached++;
+/* we know any runtime found here is valid as update_curr() precedes return */
+static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
+{
+ struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
+ s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
-#ifdef CONFIG_PREEMPTION
- /*
- * NEWIDLE balancing is a source of latency, so preemptible
- * kernels will stop after the first task is detached to minimize
- * the critical section.
- */
- if (env->idle == CPU_NEWLY_IDLE)
- break;
-#endif
+ if (slack_runtime <= 0)
+ return;
- /*
- * We only want to steal up to the prescribed amount of
- * load/util/tasks.
- */
- if (env->imbalance <= 0)
- break;
+ raw_spin_lock(&cfs_b->lock);
+ if (cfs_b->quota != RUNTIME_INF) {
+ cfs_b->runtime += slack_runtime;
- continue;
-next:
- list_move(&p->se.group_node, tasks);
+ /* we are under rq->lock, defer unthrottling using a timer */
+ if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
+ !list_empty(&cfs_b->throttled_cfs_rq))
+ start_cfs_slack_bandwidth(cfs_b);
}
+ raw_spin_unlock(&cfs_b->lock);
- /*
- * Right now, this is one of only two places we collect this stat
- * so we can safely collect detach_one_task() stats here rather
- * than inside detach_one_task().
- */
- schedstat_add(env->sd->lb_gained[env->idle], detached);
-
- return detached;
-}
-
-/*
- * attach_task() -- attach the task detached by detach_task() to its new rq.
- */
-static void attach_task(struct rq *rq, struct task_struct *p)
-{
- lockdep_assert_rq_held(rq);
-
- WARN_ON_ONCE(task_rq(p) != rq);
- activate_task(rq, p, ENQUEUE_NOCLOCK);
- wakeup_preempt(rq, p, 0);
+ /* even if it's not valid for return we don't want to try again */
+ cfs_rq->runtime_remaining -= slack_runtime;
}
-/*
- * attach_one_task() -- attaches the task returned from detach_one_task() to
- * its new rq.
- */
-static void attach_one_task(struct rq *rq, struct task_struct *p)
+static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
- struct rq_flags rf;
+ if (!cfs_bandwidth_used())
+ return;
- rq_lock(rq, &rf);
- update_rq_clock(rq);
- attach_task(rq, p);
- rq_unlock(rq, &rf);
+ if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
+ return;
+
+ __return_cfs_rq_runtime(cfs_rq);
}
/*
- * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
- * new rq.
+ * This is done with a timer (instead of inline with bandwidth return) since
+ * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
*/
-static void attach_tasks(struct lb_env *env)
+static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
{
- struct list_head *tasks = &env->tasks;
- struct task_struct *p;
- struct rq_flags rf;
-
- rq_lock(env->dst_rq, &rf);
- update_rq_clock(env->dst_rq);
+ u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
+ unsigned long flags;
- while (!list_empty(tasks)) {
- p = list_first_entry(tasks, struct task_struct, se.group_node);
- list_del_init(&p->se.group_node);
+ /* confirm we're still not at a refresh boundary */
+ raw_spin_lock_irqsave(&cfs_b->lock, flags);
+ cfs_b->slack_started = false;
- attach_task(env->dst_rq, p);
+ if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
+ raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
+ return;
}
- rq_unlock(env->dst_rq, &rf);
-}
+ if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
+ runtime = cfs_b->runtime;
-#ifdef CONFIG_NO_HZ_COMMON
-static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
-{
- if (cfs_rq->avg.load_avg)
- return true;
+ raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
- if (cfs_rq->avg.util_avg)
- return true;
+ if (!runtime)
+ return;
- return false;
+ distribute_cfs_runtime(cfs_b);
}
-static inline bool others_have_blocked(struct rq *rq)
+/*
+ * When a group wakes up we want to make sure that its quota is not already
+ * expired/exceeded, otherwise it may be allowed to steal additional ticks of
+ * runtime as update_curr() throttling can not trigger until it's on-rq.
+ */
+static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
{
- if (cpu_util_rt(rq))
- return true;
-
- if (cpu_util_dl(rq))
- return true;
+ if (!cfs_bandwidth_used())
+ return;
- if (thermal_load_avg(rq))
- return true;
+ /* an active group must be handled by the update_curr()->put() path */
+ if (!cfs_rq->runtime_enabled || cfs_rq->curr)
+ return;
- if (cpu_util_irq(rq))
- return true;
+ /* ensure the group is not already throttled */
+ if (cfs_rq_throttled(cfs_rq))
+ return;
- return false;
+ /* update runtime allocation */
+ account_cfs_rq_runtime(cfs_rq, 0);
+ if (cfs_rq->runtime_remaining <= 0)
+ throttle_cfs_rq(cfs_rq);
}
-static inline void update_blocked_load_tick(struct rq *rq)
+static void sync_throttle(struct task_group *tg, int cpu)
{
- WRITE_ONCE(rq->last_blocked_load_update_tick, jiffies);
-}
+ struct cfs_rq *pcfs_rq, *cfs_rq;
-static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
-{
- if (!has_blocked)
- rq->has_blocked_load = 0;
+ if (!cfs_bandwidth_used())
+ return;
+
+ if (!tg->parent)
+ return;
+
+ cfs_rq = tg->cfs_rq[cpu];
+ pcfs_rq = tg->parent->cfs_rq[cpu];
+
+ cfs_rq->throttle_count = pcfs_rq->throttle_count;
+ cfs_rq->throttled_clock_pelt = rq_clock_pelt(cpu_rq(cpu));
}
-#else
-static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; }
-static inline bool others_have_blocked(struct rq *rq) { return false; }
-static inline void update_blocked_load_tick(struct rq *rq) {}
-static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {}
-#endif
-static bool __update_blocked_others(struct rq *rq, bool *done)
+/* conditionally throttle active cfs_rq's from put_prev_entity() */
+static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
- const struct sched_class *curr_class;
- u64 now = rq_clock_pelt(rq);
- unsigned long thermal_pressure;
- bool decayed;
+ if (!cfs_bandwidth_used())
+ return false;
+
+ if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
+ return false;
/*
- * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
- * DL and IRQ signals have been updated before updating CFS.
+ * it's possible for a throttled entity to be forced into a running
+ * state (e.g. set_curr_task), in this case we're finished.
*/
- curr_class = rq->curr->sched_class;
+ if (cfs_rq_throttled(cfs_rq))
+ return true;
- thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
+ return throttle_cfs_rq(cfs_rq);
+}
- decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
- update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
- update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
- update_irq_load_avg(rq, 0);
+static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
+{
+ struct cfs_bandwidth *cfs_b =
+ container_of(timer, struct cfs_bandwidth, slack_timer);
- if (others_have_blocked(rq))
- *done = false;
+ do_sched_cfs_slack_timer(cfs_b);
- return decayed;
+ return HRTIMER_NORESTART;
}
-#ifdef CONFIG_FAIR_GROUP_SCHED
+extern const u64 max_cfs_quota_period;
-static bool __update_blocked_fair(struct rq *rq, bool *done)
+static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
- struct cfs_rq *cfs_rq, *pos;
- bool decayed = false;
- int cpu = cpu_of(rq);
-
- /*
- * Iterates the task_group tree in a bottom up fashion, see
- * list_add_leaf_cfs_rq() for details.
- */
- for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
- struct sched_entity *se;
+ struct cfs_bandwidth *cfs_b =
+ container_of(timer, struct cfs_bandwidth, period_timer);
+ unsigned long flags;
+ int overrun;
+ int idle = 0;
+ int count = 0;
- if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
- update_tg_load_avg(cfs_rq);
+ raw_spin_lock_irqsave(&cfs_b->lock, flags);
+ for (;;) {
+ overrun = hrtimer_forward_now(timer, cfs_b->period);
+ if (!overrun)
+ break;
- if (cfs_rq->nr_running == 0)
- update_idle_cfs_rq_clock_pelt(cfs_rq);
+ idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
- if (cfs_rq == &rq->cfs)
- decayed = true;
- }
+ if (++count > 3) {
+ u64 new, old = ktime_to_ns(cfs_b->period);
- /* Propagate pending load changes to the parent, if any: */
- se = cfs_rq->tg->se[cpu];
- if (se && !skip_blocked_update(se))
- update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
+ /*
+ * Grow period by a factor of 2 to avoid losing precision.
+ * Precision loss in the quota/period ratio can cause __cfs_schedulable
+ * to fail.
+ */
+ new = old * 2;
+ if (new < max_cfs_quota_period) {
+ cfs_b->period = ns_to_ktime(new);
+ cfs_b->quota *= 2;
+ cfs_b->burst *= 2;
- /*
- * There can be a lot of idle CPU cgroups. Don't let fully
- * decayed cfs_rqs linger on the list.
- */
- if (cfs_rq_is_decayed(cfs_rq))
- list_del_leaf_cfs_rq(cfs_rq);
+ pr_warn_ratelimited(
+ "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
+ smp_processor_id(),
+ div_u64(new, NSEC_PER_USEC),
+ div_u64(cfs_b->quota, NSEC_PER_USEC));
+ } else {
+ pr_warn_ratelimited(
+ "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
+ smp_processor_id(),
+ div_u64(old, NSEC_PER_USEC),
+ div_u64(cfs_b->quota, NSEC_PER_USEC));
+ }
- /* Don't need periodic decay once load/util_avg are null */
- if (cfs_rq_has_blocked(cfs_rq))
- *done = false;
+ /* reset count so we don't come right back in here */
+ count = 0;
+ }
}
+ if (idle)
+ cfs_b->period_active = 0;
+ raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
- return decayed;
+ return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}
-/*
- * Compute the hierarchical load factor for cfs_rq and all its ascendants.
- * This needs to be done in a top-down fashion because the load of a child
- * group is a fraction of its parents load.
- */
-static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
+void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth *parent)
{
- struct rq *rq = rq_of(cfs_rq);
- struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
- unsigned long now = jiffies;
- unsigned long load;
-
- if (cfs_rq->last_h_load_update == now)
- return;
-
- WRITE_ONCE(cfs_rq->h_load_next, NULL);
- for_each_sched_entity(se) {
- cfs_rq = cfs_rq_of(se);
- WRITE_ONCE(cfs_rq->h_load_next, se);
- if (cfs_rq->last_h_load_update == now)
- break;
- }
+ raw_spin_lock_init(&cfs_b->lock);
+ cfs_b->runtime = 0;
+ cfs_b->quota = RUNTIME_INF;
+ cfs_b->period = ns_to_ktime(default_cfs_period());
+ cfs_b->burst = 0;
+ cfs_b->hierarchical_quota = parent ? parent->hierarchical_quota : RUNTIME_INF;
- if (!se) {
- cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
- cfs_rq->last_h_load_update = now;
- }
+ INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
+ hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
+ cfs_b->period_timer.function = sched_cfs_period_timer;
- while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
- load = cfs_rq->h_load;
- load = div64_ul(load * se->avg.load_avg,
- cfs_rq_load_avg(cfs_rq) + 1);
- cfs_rq = group_cfs_rq(se);
- cfs_rq->h_load = load;
- cfs_rq->last_h_load_update = now;
- }
+ /* Add a random offset so that timers interleave */
+ hrtimer_set_expires(&cfs_b->period_timer,
+ get_random_u32_below(cfs_b->period));
+ hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ cfs_b->slack_timer.function = sched_cfs_slack_timer;
+ cfs_b->slack_started = false;
}
-static unsigned long task_h_load(struct task_struct *p)
+static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
- struct cfs_rq *cfs_rq = task_cfs_rq(p);
-
- update_cfs_rq_h_load(cfs_rq);
- return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
- cfs_rq_load_avg(cfs_rq) + 1);
+ cfs_rq->runtime_enabled = 0;
+ INIT_LIST_HEAD(&cfs_rq->throttled_list);
+ INIT_LIST_HEAD(&cfs_rq->throttled_csd_list);
}
-#else
-static bool __update_blocked_fair(struct rq *rq, bool *done)
-{
- struct cfs_rq *cfs_rq = &rq->cfs;
- bool decayed;
- decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
- if (cfs_rq_has_blocked(cfs_rq))
- *done = false;
+void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
+{
+ lockdep_assert_held(&cfs_b->lock);
- return decayed;
-}
+ if (cfs_b->period_active)
+ return;
-static unsigned long task_h_load(struct task_struct *p)
-{
- return p->se.avg.load_avg;
+ cfs_b->period_active = 1;
+ hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
+ hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
}
-#endif
-static void sched_balance_update_blocked_averages(int cpu)
+static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
- bool decayed = false, done = true;
- struct rq *rq = cpu_rq(cpu);
- struct rq_flags rf;
+ int __maybe_unused i;
- rq_lock_irqsave(rq, &rf);
- update_blocked_load_tick(rq);
- update_rq_clock(rq);
+ /* init_cfs_bandwidth() was not called */
+ if (!cfs_b->throttled_cfs_rq.next)
+ return;
- decayed |= __update_blocked_others(rq, &done);
- decayed |= __update_blocked_fair(rq, &done);
+ hrtimer_cancel(&cfs_b->period_timer);
+ hrtimer_cancel(&cfs_b->slack_timer);
- update_blocked_load_status(rq, !done);
- if (decayed)
- cpufreq_update_util(rq, 0);
- rq_unlock_irqrestore(rq, &rf);
-}
+ /*
+ * It is possible that we still have some cfs_rq's pending on a CSD
+ * list, though this race is very rare. In order for this to occur, we
+ * must have raced with the last task leaving the group while there
+ * exist throttled cfs_rq(s), and the period_timer must have queued the
+ * CSD item but the remote cpu has not yet processed it. To handle this,
+ * we can simply flush all pending CSD work inline here. We're
+ * guaranteed at this point that no additional cfs_rq of this group can
+ * join a CSD list.
+ */
+#ifdef CONFIG_SMP
+ for_each_possible_cpu(i) {
+ struct rq *rq = cpu_rq(i);
+ unsigned long flags;
-/********** Helpers for sched_balance_find_src_group ************************/
+ if (list_empty(&rq->cfsb_csd_list))
+ continue;
-/*
- * sg_lb_stats - stats of a sched_group required for load-balancing:
- */
-struct sg_lb_stats {
- unsigned long avg_load; /* Avg load over the CPUs of the group */
- unsigned long group_load; /* Total load over the CPUs of the group */
- unsigned long group_capacity; /* Capacity over the CPUs of the group */
- unsigned long group_util; /* Total utilization over the CPUs of the group */
- unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
- unsigned int sum_nr_running; /* Nr of all tasks running in the group */
- unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
- unsigned int idle_cpus; /* Nr of idle CPUs in the group */
- unsigned int group_weight;
- enum group_type group_type;
- unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
- unsigned int group_smt_balance; /* Task on busy SMT be moved */
- unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
-#ifdef CONFIG_NUMA_BALANCING
- unsigned int nr_numa_running;
- unsigned int nr_preferred_running;
+ local_irq_save(flags);
+ __cfsb_csd_unthrottle(rq);
+ local_irq_restore(flags);
+ }
#endif
-};
+}
/*
- * sd_lb_stats - stats of a sched_domain required for load-balancing:
+ * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
+ *
+ * The race is harmless, since modifying bandwidth settings of unhooked group
+ * bits doesn't do much.
*/
-struct sd_lb_stats {
- struct sched_group *busiest; /* Busiest group in this sd */
- struct sched_group *local; /* Local group in this sd */
- unsigned long total_load; /* Total load of all groups in sd */
- unsigned long total_capacity; /* Total capacity of all groups in sd */
- unsigned long avg_load; /* Average load across all groups in sd */
- unsigned int prefer_sibling; /* Tasks should go to sibling first */
-
- struct sg_lb_stats busiest_stat; /* Statistics of the busiest group */
- struct sg_lb_stats local_stat; /* Statistics of the local group */
-};
-static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
-{
- /*
- * Skimp on the clearing to avoid duplicate work. We can avoid clearing
- * local_stat because update_sg_lb_stats() does a full clear/assignment.
- * We must however set busiest_stat::group_type and
- * busiest_stat::idle_cpus to the worst busiest group because
- * update_sd_pick_busiest() reads these before assignment.
- */
- *sds = (struct sd_lb_stats){
- .busiest = NULL,
- .local = NULL,
- .total_load = 0UL,
- .total_capacity = 0UL,
- .busiest_stat = {
- .idle_cpus = UINT_MAX,
- .group_type = group_has_spare,
- },
- };
+/* cpu online callback */
+static void __maybe_unused update_runtime_enabled(struct rq *rq)
+{
+ struct task_group *tg;
+
+ lockdep_assert_rq_held(rq);
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(tg, &task_groups, list) {
+ struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
+ struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
+
+ raw_spin_lock(&cfs_b->lock);
+ cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
+ raw_spin_unlock(&cfs_b->lock);
+ }
+ rcu_read_unlock();
}
-static unsigned long scale_rt_capacity(int cpu)
+/* cpu offline callback */
+static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
{
- struct rq *rq = cpu_rq(cpu);
- unsigned long max = arch_scale_cpu_capacity(cpu);
- unsigned long used, free;
- unsigned long irq;
-
- irq = cpu_util_irq(rq);
+ struct task_group *tg;
- if (unlikely(irq >= max))
- return 1;
+ lockdep_assert_rq_held(rq);
/*
- * avg_rt.util_avg and avg_dl.util_avg track binary signals
- * (running and not running) with weights 0 and 1024 respectively.
- * avg_thermal.load_avg tracks thermal pressure and the weighted
- * average uses the actual delta max capacity(load).
+ * The rq clock has already been updated in the
+ * set_rq_offline(), so we should skip updating
+ * the rq clock again in unthrottle_cfs_rq().
*/
- used = cpu_util_rt(rq);
- used += cpu_util_dl(rq);
- used += thermal_load_avg(rq);
+ rq_clock_start_loop_update(rq);
- if (unlikely(used >= max))
- return 1;
+ rcu_read_lock();
+ list_for_each_entry_rcu(tg, &task_groups, list) {
+ struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
+
+ if (!cfs_rq->runtime_enabled)
+ continue;
+
+ /*
+ * clock_task is not advancing so we just need to make sure
+ * there's some valid quota amount
+ */
+ cfs_rq->runtime_remaining = 1;
+ /*
+ * Offline rq is schedulable till CPU is completely disabled
+ * in take_cpu_down(), so we prevent new cfs throttling here.
+ */
+ cfs_rq->runtime_enabled = 0;
- free = max - used;
+ if (cfs_rq_throttled(cfs_rq))
+ unthrottle_cfs_rq(cfs_rq);
+ }
+ rcu_read_unlock();
- return scale_irq_capacity(free, irq, max);
+ rq_clock_stop_loop_update(rq);
}
-static void update_cpu_capacity(struct sched_domain *sd, int cpu)
+bool cfs_task_bw_constrained(struct task_struct *p)
{
- unsigned long capacity = scale_rt_capacity(cpu);
- struct sched_group *sdg = sd->groups;
+ struct cfs_rq *cfs_rq = task_cfs_rq(p);
- if (!capacity)
- capacity = 1;
+ if (!cfs_bandwidth_used())
+ return false;
- cpu_rq(cpu)->cpu_capacity = capacity;
- trace_sched_cpu_capacity_tp(cpu_rq(cpu));
+ if (cfs_rq->runtime_enabled ||
+ tg_cfs_bandwidth(cfs_rq->tg)->hierarchical_quota != RUNTIME_INF)
+ return true;
- sdg->sgc->capacity = capacity;
- sdg->sgc->min_capacity = capacity;
- sdg->sgc->max_capacity = capacity;
+ return false;
}
-void update_group_capacity(struct sched_domain *sd, int cpu)
+#ifdef CONFIG_NO_HZ_FULL
+/* called from pick_next_task_fair() */
+static void sched_fair_update_stop_tick(struct rq *rq, struct task_struct *p)
{
- struct sched_domain *child = sd->child;
- struct sched_group *group, *sdg = sd->groups;
- unsigned long capacity, min_capacity, max_capacity;
- unsigned long interval;
-
- interval = msecs_to_jiffies(sd->balance_interval);
- interval = clamp(interval, 1UL, max_load_balance_interval);
- sdg->sgc->next_update = jiffies + interval;
+ int cpu = cpu_of(rq);
- if (!child) {
- update_cpu_capacity(sd, cpu);
+ if (!sched_feat(HZ_BW) || !cfs_bandwidth_used())
return;
- }
-
- capacity = 0;
- min_capacity = ULONG_MAX;
- max_capacity = 0;
-
- if (child->flags & SD_OVERLAP) {
- /*
- * SD_OVERLAP domains cannot assume that child groups
- * span the current group.
- */
-
- for_each_cpu(cpu, sched_group_span(sdg)) {
- unsigned long cpu_cap = capacity_of(cpu);
-
- capacity += cpu_cap;
- min_capacity = min(cpu_cap, min_capacity);
- max_capacity = max(cpu_cap, max_capacity);
- }
- } else {
- /*
- * !SD_OVERLAP domains can assume that child groups
- * span the current group.
- */
- group = child->groups;
- do {
- struct sched_group_capacity *sgc = group->sgc;
+ if (!tick_nohz_full_cpu(cpu))
+ return;
- capacity += sgc->capacity;
- min_capacity = min(sgc->min_capacity, min_capacity);
- max_capacity = max(sgc->max_capacity, max_capacity);
- group = group->next;
- } while (group != child->groups);
- }
+ if (rq->nr_running != 1)
+ return;
- sdg->sgc->capacity = capacity;
- sdg->sgc->min_capacity = min_capacity;
- sdg->sgc->max_capacity = max_capacity;
+ /*
+ * We know there is only one task runnable and we've just picked it. The
+ * normal enqueue path will have cleared TICK_DEP_BIT_SCHED if we will
+ * be otherwise able to stop the tick. Just need to check if we are using
+ * bandwidth control.
+ */
+ if (cfs_task_bw_constrained(p))
+ tick_nohz_dep_set_cpu(cpu, TICK_DEP_BIT_SCHED);
}
+#endif
-/*
- * Check whether the capacity of the rq has been noticeably reduced by side
- * activity. The imbalance_pct is used for the threshold.
- * Return true is the capacity is reduced
- */
-static inline int
-check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
-{
- return ((rq->cpu_capacity * sd->imbalance_pct) <
- (arch_scale_cpu_capacity(cpu_of(rq)) * 100));
-}
+#else /* CONFIG_CFS_BANDWIDTH */
-/* Check if the rq has a misfit task */
-static inline bool check_misfit_status(struct rq *rq)
+static inline bool cfs_bandwidth_used(void)
{
- return rq->misfit_task_load;
+ return false;
}
-/*
- * Group imbalance indicates (and tries to solve) the problem where balancing
- * groups is inadequate due to ->cpus_ptr constraints.
- *
- * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
- * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
- * Something like:
- *
- * { 0 1 2 3 } { 4 5 6 7 }
- * * * * *
- *
- * If we were to balance group-wise we'd place two tasks in the first group and
- * two tasks in the second group. Clearly this is undesired as it will overload
- * cpu 3 and leave one of the CPUs in the second group unused.
- *
- * The current solution to this issue is detecting the skew in the first group
- * by noticing the lower domain failed to reach balance and had difficulty
- * moving tasks due to affinity constraints.
- *
- * When this is so detected; this group becomes a candidate for busiest; see
- * update_sd_pick_busiest(). And calculate_imbalance() and
- * sched_balance_find_src_group() avoid some of the usual balance conditions to allow it
- * to create an effective group imbalance.
- *
- * This is a somewhat tricky proposition since the next run might not find the
- * group imbalance and decide the groups need to be balanced again. A most
- * subtle and fragile situation.
- */
+static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
+static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
+static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
+static inline void sync_throttle(struct task_group *tg, int cpu) {}
+static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
-static inline int sg_imbalanced(struct sched_group *group)
+static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
- return group->sgc->imbalance;
+ return 0;
}
-/*
- * group_has_capacity returns true if the group has spare capacity that could
- * be used by some tasks.
- * We consider that a group has spare capacity if the number of task is
- * smaller than the number of CPUs or if the utilization is lower than the
- * available capacity for CFS tasks.
- * For the latter, we use a threshold to stabilize the state, to take into
- * account the variance of the tasks' load and to return true if the available
- * capacity in meaningful for the load balancer.
- * As an example, an available capacity of 1% can appear but it doesn't make
- * any benefit for the load balance.
- */
-static inline bool
-group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
+static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
- if (sgs->sum_nr_running < sgs->group_weight)
- return true;
-
- if ((sgs->group_capacity * imbalance_pct) <
- (sgs->group_runnable * 100))
- return false;
+ return 0;
+}
- if ((sgs->group_capacity * 100) >
- (sgs->group_util * imbalance_pct))
- return true;
+#ifdef CONFIG_FAIR_GROUP_SCHED
+void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth *parent) {}
+static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
+#endif
- return false;
+static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
+{
+ return NULL;
}
-
-/*
- * group_is_overloaded returns true if the group has more tasks than it can
- * handle.
- * group_is_overloaded is not equals to !group_has_capacity because a group
- * with the exact right number of tasks, has no more spare capacity but is not
- * overloaded so both group_has_capacity and group_is_overloaded return
- * false.
- */
-static inline bool
-group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
+static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
+static inline void update_runtime_enabled(struct rq *rq) {}
+static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
+#ifdef CONFIG_CGROUP_SCHED
+bool cfs_task_bw_constrained(struct task_struct *p)
{
- if (sgs->sum_nr_running <= sgs->group_weight)
- return false;
-
- if ((sgs->group_capacity * 100) <
- (sgs->group_util * imbalance_pct))
- return true;
-
- if ((sgs->group_capacity * imbalance_pct) <
- (sgs->group_runnable * 100))
- return true;
-
return false;
}
+#endif
+#endif /* CONFIG_CFS_BANDWIDTH */
-static inline enum
-group_type group_classify(unsigned int imbalance_pct,
- struct sched_group *group,
- struct sg_lb_stats *sgs)
-{
- if (group_is_overloaded(imbalance_pct, sgs))
- return group_overloaded;
-
- if (sg_imbalanced(group))
- return group_imbalanced;
+#if !defined(CONFIG_CFS_BANDWIDTH) || !defined(CONFIG_NO_HZ_FULL)
+static inline void sched_fair_update_stop_tick(struct rq *rq, struct task_struct *p) {}
+#endif
- if (sgs->group_asym_packing)
- return group_asym_packing;
+/**************************************************
+ * CFS operations on tasks:
+ */
- if (sgs->group_smt_balance)
- return group_smt_balance;
+#ifdef CONFIG_SCHED_HRTICK
+static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
+{
+ struct sched_entity *se = &p->se;
- if (sgs->group_misfit_task_load)
- return group_misfit_task;
+ SCHED_WARN_ON(task_rq(p) != rq);
- if (!group_has_capacity(imbalance_pct, sgs))
- return group_fully_busy;
+ if (rq->cfs.h_nr_running > 1) {
+ u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
+ u64 slice = se->slice;
+ s64 delta = slice - ran;
- return group_has_spare;
+ if (delta < 0) {
+ if (task_current(rq, p))
+ resched_curr(rq);
+ return;
+ }
+ hrtick_start(rq, delta);
+ }
}
-/**
- * sched_use_asym_prio - Check whether asym_packing priority must be used
- * @sd: The scheduling domain of the load balancing
- * @cpu: A CPU
- *
- * Always use CPU priority when balancing load between SMT siblings. When
- * balancing load between cores, it is not sufficient that @cpu is idle. Only
- * use CPU priority if the whole core is idle.
- *
- * Returns: True if the priority of @cpu must be followed. False otherwise.
+/*
+ * called from enqueue/dequeue and updates the hrtick when the
+ * current task is from our class and nr_running is low enough
+ * to matter.
*/
-static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
+static void hrtick_update(struct rq *rq)
{
- if (!(sd->flags & SD_ASYM_PACKING))
- return false;
+ struct task_struct *curr = rq->curr;
- if (!sched_smt_active())
- return true;
+ if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class)
+ return;
- return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu);
+ hrtick_start_fair(rq, curr);
}
-
-static inline bool sched_asym(struct sched_domain *sd, int dst_cpu, int src_cpu)
+#else /* !CONFIG_SCHED_HRTICK */
+static inline void
+hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
- /*
- * First check if @dst_cpu can do asym_packing load balance. Only do it
- * if it has higher priority than @src_cpu.
- */
- return sched_use_asym_prio(sd, dst_cpu) &&
- sched_asym_prefer(dst_cpu, src_cpu);
}
-/**
- * sched_group_asym - Check if the destination CPU can do asym_packing balance
- * @env: The load balancing environment
- * @sgs: Load-balancing statistics of the candidate busiest group
- * @group: The candidate busiest group
- *
- * @env::dst_cpu can do asym_packing if it has higher priority than the
- * preferred CPU of @group.
- *
- * Return: true if @env::dst_cpu can do with asym_packing load balance. False
- * otherwise.
- */
-static inline bool
-sched_group_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
+static inline void hrtick_update(struct rq *rq)
{
- /*
- * CPU priorities do not make sense for SMT cores with more than one
- * busy sibling.
- */
- if ((group->flags & SD_SHARE_CPUCAPACITY) &&
- (sgs->group_weight - sgs->idle_cpus != 1))
- return false;
-
- return sched_asym(env->sd, env->dst_cpu, group->asym_prefer_cpu);
}
+#endif
-/* One group has more than one SMT CPU while the other group does not */
-static inline bool smt_vs_nonsmt_groups(struct sched_group *sg1,
- struct sched_group *sg2)
+/* Runqueue only has SCHED_IDLE tasks enqueued */
+static int sched_idle_rq(struct rq *rq)
{
- if (!sg1 || !sg2)
- return false;
-
- return (sg1->flags & SD_SHARE_CPUCAPACITY) !=
- (sg2->flags & SD_SHARE_CPUCAPACITY);
+ return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running &&
+ rq->nr_running);
}
-static inline bool smt_balance(struct lb_env *env, struct sg_lb_stats *sgs,
- struct sched_group *group)
+#ifdef CONFIG_SMP
+int sched_idle_cpu(int cpu)
{
- if (!env->idle)
- return false;
-
- /*
- * For SMT source group, it is better to move a task
- * to a CPU that doesn't have multiple tasks sharing its CPU capacity.
- * Note that if a group has a single SMT, SD_SHARE_CPUCAPACITY
- * will not be on.
- */
- if (group->flags & SD_SHARE_CPUCAPACITY &&
- sgs->sum_h_nr_running > 1)
- return true;
-
- return false;
+ return sched_idle_rq(cpu_rq(cpu));
}
+#endif
-static inline long sibling_imbalance(struct lb_env *env,
- struct sd_lb_stats *sds,
- struct sg_lb_stats *busiest,
- struct sg_lb_stats *local)
+/*
+ * The enqueue_task method is called before nr_running is
+ * increased. Here we update the fair scheduling stats and
+ * then put the task into the rbtree:
+ */
+static void
+enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
- int ncores_busiest, ncores_local;
- long imbalance;
-
- if (!env->idle || !busiest->sum_nr_running)
- return 0;
-
- ncores_busiest = sds->busiest->cores;
- ncores_local = sds->local->cores;
-
- if (ncores_busiest == ncores_local) {
- imbalance = busiest->sum_nr_running;
- lsub_positive(&imbalance, local->sum_nr_running);
- return imbalance;
- }
-
- /* Balance such that nr_running/ncores ratio are same on both groups */
- imbalance = ncores_local * busiest->sum_nr_running;
- lsub_positive(&imbalance, ncores_busiest * local->sum_nr_running);
- /* Normalize imbalance and do rounding on normalization */
- imbalance = 2 * imbalance + ncores_local + ncores_busiest;
- imbalance /= ncores_local + ncores_busiest;
-
- /* Take advantage of resource in an empty sched group */
- if (imbalance <= 1 && local->sum_nr_running == 0 &&
- busiest->sum_nr_running > 1)
- imbalance = 2;
-
- return imbalance;
-}
+ struct cfs_rq *cfs_rq;
+ struct sched_entity *se = &p->se;
+ int idle_h_nr_running = task_has_idle_policy(p);
+ int task_new = !(flags & ENQUEUE_WAKEUP);
-static inline bool
-sched_reduced_capacity(struct rq *rq, struct sched_domain *sd)
-{
/*
- * When there is more than 1 task, the group_overloaded case already
- * takes care of cpu with reduced capacity
+ * The code below (indirectly) updates schedutil which looks at
+ * the cfs_rq utilization to select a frequency.
+ * Let's add the task's estimated utilization to the cfs_rq's
+ * estimated utilization, before we update schedutil.
*/
- if (rq->cfs.h_nr_running != 1)
- return false;
-
- return check_cpu_capacity(rq, sd);
-}
-
-/**
- * update_sg_lb_stats - Update sched_group's statistics for load balancing.
- * @env: The load balancing environment.
- * @sds: Load-balancing data with statistics of the local group.
- * @group: sched_group whose statistics are to be updated.
- * @sgs: variable to hold the statistics for this group.
- * @sg_overloaded: sched_group is overloaded
- * @sg_overutilized: sched_group is overutilized
- */
-static inline void update_sg_lb_stats(struct lb_env *env,
- struct sd_lb_stats *sds,
- struct sched_group *group,
- struct sg_lb_stats *sgs,
- bool *sg_overloaded,
- bool *sg_overutilized)
-{
- int i, nr_running, local_group;
-
- memset(sgs, 0, sizeof(*sgs));
-
- local_group = group == sds->local;
-
- for_each_cpu_and(i, sched_group_span(group), env->cpus) {
- struct rq *rq = cpu_rq(i);
- unsigned long load = cpu_load(rq);
-
- sgs->group_load += load;
- sgs->group_util += cpu_util_cfs(i);
- sgs->group_runnable += cpu_runnable(rq);
- sgs->sum_h_nr_running += rq->cfs.h_nr_running;
+ util_est_enqueue(&rq->cfs, p);
- nr_running = rq->nr_running;
- sgs->sum_nr_running += nr_running;
+ /*
+ * If in_iowait is set, the code below may not trigger any cpufreq
+ * utilization updates, so do it here explicitly with the IOWAIT flag
+ * passed.
+ */
+ if (p->in_iowait)
+ cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
- if (nr_running > 1)
- *sg_overloaded = 1;
+ for_each_sched_entity(se) {
+ if (se->on_rq)
+ break;
+ cfs_rq = cfs_rq_of(se);
+ enqueue_entity(cfs_rq, se, flags);
- if (cpu_overutilized(i))
- *sg_overutilized = 1;
+ cfs_rq->h_nr_running++;
+ cfs_rq->idle_h_nr_running += idle_h_nr_running;
-#ifdef CONFIG_NUMA_BALANCING
- sgs->nr_numa_running += rq->nr_numa_running;
- sgs->nr_preferred_running += rq->nr_preferred_running;
-#endif
- /*
- * No need to call idle_cpu() if nr_running is not 0
- */
- if (!nr_running && idle_cpu(i)) {
- sgs->idle_cpus++;
- /* Idle cpu can't have misfit task */
- continue;
- }
+ if (cfs_rq_is_idle(cfs_rq))
+ idle_h_nr_running = 1;
- if (local_group)
- continue;
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(cfs_rq))
+ goto enqueue_throttle;
- if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
- /* Check for a misfit task on the cpu */
- if (sgs->group_misfit_task_load < rq->misfit_task_load) {
- sgs->group_misfit_task_load = rq->misfit_task_load;
- *sg_overloaded = 1;
- }
- } else if (env->idle && sched_reduced_capacity(rq, env->sd)) {
- /* Check for a task running on a CPU with reduced capacity */
- if (sgs->group_misfit_task_load < load)
- sgs->group_misfit_task_load = load;
- }
+ flags = ENQUEUE_WAKEUP;
}
- sgs->group_capacity = group->sgc->capacity;
-
- sgs->group_weight = group->group_weight;
-
- /* Check if dst CPU is idle and preferred to this group */
- if (!local_group && env->idle && sgs->sum_h_nr_running &&
- sched_group_asym(env, sgs, group))
- sgs->group_asym_packing = 1;
+ for_each_sched_entity(se) {
+ cfs_rq = cfs_rq_of(se);
- /* Check for loaded SMT group to be balanced to dst CPU */
- if (!local_group && smt_balance(env, sgs, group))
- sgs->group_smt_balance = 1;
+ update_load_avg(cfs_rq, se, UPDATE_TG);
+ se_update_runnable(se);
+ update_cfs_group(se);
- sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
+ cfs_rq->h_nr_running++;
+ cfs_rq->idle_h_nr_running += idle_h_nr_running;
- /* Computing avg_load makes sense only when group is overloaded */
- if (sgs->group_type == group_overloaded)
- sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
- sgs->group_capacity;
-}
+ if (cfs_rq_is_idle(cfs_rq))
+ idle_h_nr_running = 1;
-/**
- * update_sd_pick_busiest - return 1 on busiest group
- * @env: The load balancing environment.
- * @sds: sched_domain statistics
- * @sg: sched_group candidate to be checked for being the busiest
- * @sgs: sched_group statistics
- *
- * Determine if @sg is a busier group than the previously selected
- * busiest group.
- *
- * Return: %true if @sg is a busier group than the previously selected
- * busiest group. %false otherwise.
- */
-static bool update_sd_pick_busiest(struct lb_env *env,
- struct sd_lb_stats *sds,
- struct sched_group *sg,
- struct sg_lb_stats *sgs)
-{
- struct sg_lb_stats *busiest = &sds->busiest_stat;
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(cfs_rq))
+ goto enqueue_throttle;
+ }
- /* Make sure that there is at least one task to pull */
- if (!sgs->sum_h_nr_running)
- return false;
+ /* At this point se is NULL and we are at root level*/
+ add_nr_running(rq, 1);
/*
- * Don't try to pull misfit tasks we can't help.
- * We can use max_capacity here as reduction in capacity on some
- * CPUs in the group should either be possible to resolve
- * internally or be covered by avg_load imbalance (eventually).
+ * Since new tasks are assigned an initial util_avg equal to
+ * half of the spare capacity of their CPU, tiny tasks have the
+ * ability to cross the overutilized threshold, which will
+ * result in the load balancer ruining all the task placement
+ * done by EAS. As a way to mitigate that effect, do not account
+ * for the first enqueue operation of new tasks during the
+ * overutilized flag detection.
+ *
+ * A better way of solving this problem would be to wait for
+ * the PELT signals of tasks to converge before taking them
+ * into account, but that is not straightforward to implement,
+ * and the following generally works well enough in practice.
*/
- if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
- (sgs->group_type == group_misfit_task) &&
- (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
- sds->local_stat.group_type != group_has_spare))
- return false;
-
- if (sgs->group_type > busiest->group_type)
- return true;
-
- if (sgs->group_type < busiest->group_type)
- return false;
+ if (!task_new)
+ check_update_overutilized_status(rq);
- /*
- * The candidate and the current busiest group are the same type of
- * group. Let check which one is the busiest according to the type.
- */
+enqueue_throttle:
+ assert_list_leaf_cfs_rq(rq);
- switch (sgs->group_type) {
- case group_overloaded:
- /* Select the overloaded group with highest avg_load. */
- return sgs->avg_load > busiest->avg_load;
+ hrtick_update(rq);
+}
- case group_imbalanced:
- /*
- * Select the 1st imbalanced group as we don't have any way to
- * choose one more than another.
- */
- return false;
+static void set_next_buddy(struct sched_entity *se);
- case group_asym_packing:
- /* Prefer to move from lowest priority CPU's work */
- return sched_asym_prefer(sds->busiest->asym_prefer_cpu, sg->asym_prefer_cpu);
+/*
+ * The dequeue_task method is called before nr_running is
+ * decreased. We remove the task from the rbtree and
+ * update the fair scheduling stats:
+ */
+static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
+{
+ struct cfs_rq *cfs_rq;
+ struct sched_entity *se = &p->se;
+ int task_sleep = flags & DEQUEUE_SLEEP;
+ int idle_h_nr_running = task_has_idle_policy(p);
+ bool was_sched_idle = sched_idle_rq(rq);
- case group_misfit_task:
- /*
- * If we have more than one misfit sg go with the biggest
- * misfit.
- */
- return sgs->group_misfit_task_load > busiest->group_misfit_task_load;
+ util_est_dequeue(&rq->cfs, p);
- case group_smt_balance:
- /*
- * Check if we have spare CPUs on either SMT group to
- * choose has spare or fully busy handling.
- */
- if (sgs->idle_cpus != 0 || busiest->idle_cpus != 0)
- goto has_spare;
+ for_each_sched_entity(se) {
+ cfs_rq = cfs_rq_of(se);
+ dequeue_entity(cfs_rq, se, flags);
- fallthrough;
+ cfs_rq->h_nr_running--;
+ cfs_rq->idle_h_nr_running -= idle_h_nr_running;
- case group_fully_busy:
- /*
- * Select the fully busy group with highest avg_load. In
- * theory, there is no need to pull task from such kind of
- * group because tasks have all compute capacity that they need
- * but we can still improve the overall throughput by reducing
- * contention when accessing shared HW resources.
- *
- * XXX for now avg_load is not computed and always 0 so we
- * select the 1st one, except if @sg is composed of SMT
- * siblings.
- */
+ if (cfs_rq_is_idle(cfs_rq))
+ idle_h_nr_running = 1;
- if (sgs->avg_load < busiest->avg_load)
- return false;
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(cfs_rq))
+ goto dequeue_throttle;
- if (sgs->avg_load == busiest->avg_load) {
+ /* Don't dequeue parent if it has other entities besides us */
+ if (cfs_rq->load.weight) {
+ /* Avoid re-evaluating load for this entity: */
+ se = parent_entity(se);
/*
- * SMT sched groups need more help than non-SMT groups.
- * If @sg happens to also be SMT, either choice is good.
+ * Bias pick_next to pick a task from this cfs_rq, as
+ * p is sleeping when it is within its sched_slice.
*/
- if (sds->busiest->flags & SD_SHARE_CPUCAPACITY)
- return false;
+ if (task_sleep && se && !throttled_hierarchy(cfs_rq))
+ set_next_buddy(se);
+ break;
}
+ flags |= DEQUEUE_SLEEP;
+ }
- break;
+ for_each_sched_entity(se) {
+ cfs_rq = cfs_rq_of(se);
- case group_has_spare:
- /*
- * Do not pick sg with SMT CPUs over sg with pure CPUs,
- * as we do not want to pull task off SMT core with one task
- * and make the core idle.
- */
- if (smt_vs_nonsmt_groups(sds->busiest, sg)) {
- if (sg->flags & SD_SHARE_CPUCAPACITY && sgs->sum_h_nr_running <= 1)
- return false;
- else
- return true;
- }
-has_spare:
+ update_load_avg(cfs_rq, se, UPDATE_TG);
+ se_update_runnable(se);
+ update_cfs_group(se);
- /*
- * Select not overloaded group with lowest number of idle CPUs
- * and highest number of running tasks. We could also compare
- * the spare capacity which is more stable but it can end up
- * that the group has less spare capacity but finally more idle
- * CPUs which means less opportunity to pull tasks.
- */
- if (sgs->idle_cpus > busiest->idle_cpus)
- return false;
- else if ((sgs->idle_cpus == busiest->idle_cpus) &&
- (sgs->sum_nr_running <= busiest->sum_nr_running))
- return false;
+ cfs_rq->h_nr_running--;
+ cfs_rq->idle_h_nr_running -= idle_h_nr_running;
+
+ if (cfs_rq_is_idle(cfs_rq))
+ idle_h_nr_running = 1;
+
+ /* end evaluation on encountering a throttled cfs_rq */
+ if (cfs_rq_throttled(cfs_rq))
+ goto dequeue_throttle;
- break;
}
- /*
- * Candidate sg has no more than one task per CPU and has higher
- * per-CPU capacity. Migrating tasks to less capable CPUs may harm
- * throughput. Maximize throughput, power/energy consequences are not
- * considered.
- */
- if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
- (sgs->group_type <= group_fully_busy) &&
- (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
- return false;
+ /* At this point se is NULL and we are at root level*/
+ sub_nr_running(rq, 1);
- return true;
-}
+ /* balance early to pull high priority tasks */
+ if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
+ rq->next_balance = jiffies;
-#ifdef CONFIG_NUMA_BALANCING
-static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
-{
- if (sgs->sum_h_nr_running > sgs->nr_numa_running)
- return regular;
- if (sgs->sum_h_nr_running > sgs->nr_preferred_running)
- return remote;
- return all;
+dequeue_throttle:
+ util_est_update(&rq->cfs, p, task_sleep);
+ hrtick_update(rq);
}
-static inline enum fbq_type fbq_classify_rq(struct rq *rq)
+#ifdef CONFIG_SMP
+
+DEFINE_PER_CPU(cpumask_var_t, select_rq_mask);
+
+static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
{
- if (rq->nr_running > rq->nr_numa_running)
- return regular;
- if (rq->nr_running > rq->nr_preferred_running)
- return remote;
- return all;
+ return cfs_rq->avg.runnable_avg;
}
-#else
-static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
+
+unsigned long cpu_runnable(struct rq *rq)
{
- return all;
+ return cfs_rq_runnable_avg(&rq->cfs);
}
-static inline enum fbq_type fbq_classify_rq(struct rq *rq)
+unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
{
- return regular;
-}
-#endif /* CONFIG_NUMA_BALANCING */
+ struct cfs_rq *cfs_rq;
+ unsigned int runnable;
+
+ /* Task has no contribution or is new */
+ if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
+ return cpu_runnable(rq);
+ cfs_rq = &rq->cfs;
+ runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
-struct sg_lb_stats;
+ /* Discount task's runnable from CPU's runnable */
+ lsub_positive(&runnable, p->se.avg.runnable_avg);
-/*
- * task_running_on_cpu - return 1 if @p is running on @cpu.
- */
+ return runnable;
+}
-static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
+static void record_wakee(struct task_struct *p)
{
- /* Task has no contribution or is new */
- if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
- return 0;
-
- if (task_on_rq_queued(p))
- return 1;
+ /*
+ * Only decay a single time; tasks that have less then 1 wakeup per
+ * jiffy will not have built up many flips.
+ */
+ if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
+ current->wakee_flips >>= 1;
+ current->wakee_flip_decay_ts = jiffies;
+ }
- return 0;
+ if (current->last_wakee != p) {
+ current->last_wakee = p;
+ current->wakee_flips++;
+ }
}
-/**
- * idle_cpu_without - would a given CPU be idle without p ?
- * @cpu: the processor on which idleness is tested.
- * @p: task which should be ignored.
+/*
+ * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
+ *
+ * A waker of many should wake a different task than the one last awakened
+ * at a frequency roughly N times higher than one of its wakees.
*
- * Return: 1 if the CPU would be idle. 0 otherwise.
+ * In order to determine whether we should let the load spread vs consolidating
+ * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
+ * partner, and a factor of lls_size higher frequency in the other.
+ *
+ * With both conditions met, we can be relatively sure that the relationship is
+ * non-monogamous, with partner count exceeding socket size.
+ *
+ * Waker/wakee being client/server, worker/dispatcher, interrupt source or
+ * whatever is irrelevant, spread criteria is apparent partner count exceeds
+ * socket size.
*/
-static int idle_cpu_without(int cpu, struct task_struct *p)
+static int wake_wide(struct task_struct *p)
{
- struct rq *rq = cpu_rq(cpu);
+ unsigned int master = current->wakee_flips;
+ unsigned int slave = p->wakee_flips;
+ int factor = __this_cpu_read(sd_llc_size);
- if (rq->curr != rq->idle && rq->curr != p)
+ if (master < slave)
+ swap(master, slave);
+ if (slave < factor || master < slave * factor)
return 0;
+ return 1;
+}
+/*
+ * The purpose of wake_affine() is to quickly determine on which CPU we can run
+ * soonest. For the purpose of speed we only consider the waking and previous
+ * CPU.
+ *
+ * wake_affine_idle() - only considers 'now', it check if the waking CPU is
+ * cache-affine and is (or will be) idle.
+ *
+ * wake_affine_weight() - considers the weight to reflect the average
+ * scheduling latency of the CPUs. This seems to work
+ * for the overloaded case.
+ */
+static int
+wake_affine_idle(int this_cpu, int prev_cpu, int sync)
+{
/*
- * rq->nr_running can't be used but an updated version without the
- * impact of p on cpu must be used instead. The updated nr_running
- * be computed and tested before calling idle_cpu_without().
+ * If this_cpu is idle, it implies the wakeup is from interrupt
+ * context. Only allow the move if cache is shared. Otherwise an
+ * interrupt intensive workload could force all tasks onto one
+ * node depending on the IO topology or IRQ affinity settings.
+ *
+ * If the prev_cpu is idle and cache affine then avoid a migration.
+ * There is no guarantee that the cache hot data from an interrupt
+ * is more important than cache hot data on the prev_cpu and from
+ * a cpufreq perspective, it's better to have higher utilisation
+ * on one CPU.
*/
+ if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
+ return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
+
+ if (sync && cpu_rq(this_cpu)->nr_running == 1)
+ return this_cpu;
- if (rq->ttwu_pending)
- return 0;
+ if (available_idle_cpu(prev_cpu))
+ return prev_cpu;
- return 1;
+ return nr_cpumask_bits;
}
-/*
- * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
- * @sd: The sched_domain level to look for idlest group.
- * @group: sched_group whose statistics are to be updated.
- * @sgs: variable to hold the statistics for this group.
- * @p: The task for which we look for the idlest group/CPU.
- */
-static inline void update_sg_wakeup_stats(struct sched_domain *sd,
- struct sched_group *group,
- struct sg_lb_stats *sgs,
- struct task_struct *p)
+static int
+wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
+ int this_cpu, int prev_cpu, int sync)
{
- int i, nr_running;
-
- memset(sgs, 0, sizeof(*sgs));
-
- /* Assume that task can't fit any CPU of the group */
- if (sd->flags & SD_ASYM_CPUCAPACITY)
- sgs->group_misfit_task_load = 1;
-
- for_each_cpu(i, sched_group_span(group)) {
- struct rq *rq = cpu_rq(i);
- unsigned int local;
-
- sgs->group_load += cpu_load_without(rq, p);
- sgs->group_util += cpu_util_without(i, p);
- sgs->group_runnable += cpu_runnable_without(rq, p);
- local = task_running_on_cpu(i, p);
- sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;
+ s64 this_eff_load, prev_eff_load;
+ unsigned long task_load;
- nr_running = rq->nr_running - local;
- sgs->sum_nr_running += nr_running;
+ this_eff_load = cpu_load(cpu_rq(this_cpu));
- /*
- * No need to call idle_cpu_without() if nr_running is not 0
- */
- if (!nr_running && idle_cpu_without(i, p))
- sgs->idle_cpus++;
+ if (sync) {
+ unsigned long current_load = task_h_load(current);
- /* Check if task fits in the CPU */
- if (sd->flags & SD_ASYM_CPUCAPACITY &&
- sgs->group_misfit_task_load &&
- task_fits_cpu(p, i))
- sgs->group_misfit_task_load = 0;
+ if (current_load > this_eff_load)
+ return this_cpu;
+ this_eff_load -= current_load;
}
- sgs->group_capacity = group->sgc->capacity;
+ task_load = task_h_load(p);
- sgs->group_weight = group->group_weight;
+ this_eff_load += task_load;
+ if (sched_feat(WA_BIAS))
+ this_eff_load *= 100;
+ this_eff_load *= capacity_of(prev_cpu);
- sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
+ prev_eff_load = cpu_load(cpu_rq(prev_cpu));
+ prev_eff_load -= task_load;
+ if (sched_feat(WA_BIAS))
+ prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
+ prev_eff_load *= capacity_of(this_cpu);
/*
- * Computing avg_load makes sense only when group is fully busy or
- * overloaded
+ * If sync, adjust the weight of prev_eff_load such that if
+ * prev_eff == this_eff that select_idle_sibling() will consider
+ * stacking the wakee on top of the waker if no other CPU is
+ * idle.
*/
- if (sgs->group_type == group_fully_busy ||
- sgs->group_type == group_overloaded)
- sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
- sgs->group_capacity;
+ if (sync)
+ prev_eff_load += 1;
+
+ return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
}
-static bool update_pick_idlest(struct sched_group *idlest,
- struct sg_lb_stats *idlest_sgs,
- struct sched_group *group,
- struct sg_lb_stats *sgs)
+static int wake_affine(struct sched_domain *sd, struct task_struct *p,
+ int this_cpu, int prev_cpu, int sync)
{
- if (sgs->group_type < idlest_sgs->group_type)
- return true;
-
- if (sgs->group_type > idlest_sgs->group_type)
- return false;
-
- /*
- * The candidate and the current idlest group are the same type of
- * group. Let check which one is the idlest according to the type.
- */
-
- switch (sgs->group_type) {
- case group_overloaded:
- case group_fully_busy:
- /* Select the group with lowest avg_load. */
- if (idlest_sgs->avg_load <= sgs->avg_load)
- return false;
- break;
-
- case group_imbalanced:
- case group_asym_packing:
- case group_smt_balance:
- /* Those types are not used in the slow wakeup path */
- return false;
-
- case group_misfit_task:
- /* Select group with the highest max capacity */
- if (idlest->sgc->max_capacity >= group->sgc->max_capacity)
- return false;
- break;
+ int target = nr_cpumask_bits;
- case group_has_spare:
- /* Select group with most idle CPUs */
- if (idlest_sgs->idle_cpus > sgs->idle_cpus)
- return false;
+ if (sched_feat(WA_IDLE))
+ target = wake_affine_idle(this_cpu, prev_cpu, sync);
- /* Select group with lowest group_util */
- if (idlest_sgs->idle_cpus == sgs->idle_cpus &&
- idlest_sgs->group_util <= sgs->group_util)
- return false;
+ if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
+ target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
- break;
- }
+ schedstat_inc(p->stats.nr_wakeups_affine_attempts);
+ if (target != this_cpu)
+ return prev_cpu;
- return true;
+ schedstat_inc(sd->ttwu_move_affine);
+ schedstat_inc(p->stats.nr_wakeups_affine);
+ return target;
}
/*
- * sched_balance_find_dst_group() finds and returns the least busy CPU group within the
- * domain.
- *
- * Assumes p is allowed on at least one CPU in sd.
+ * sched_balance_find_dst_group_cpu - find the idlest CPU among the CPUs in the group.
*/
-static struct sched_group *
-sched_balance_find_dst_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
-{
- struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
- struct sg_lb_stats local_sgs, tmp_sgs;
- struct sg_lb_stats *sgs;
- unsigned long imbalance;
- struct sg_lb_stats idlest_sgs = {
- .avg_load = UINT_MAX,
- .group_type = group_overloaded,
- };
+static int
+sched_balance_find_dst_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
+{
+ unsigned long load, min_load = ULONG_MAX;
+ unsigned int min_exit_latency = UINT_MAX;
+ u64 latest_idle_timestamp = 0;
+ int least_loaded_cpu = this_cpu;
+ int shallowest_idle_cpu = -1;
+ int i;
- do {
- int local_group;
+ /* Check if we have any choice: */
+ if (group->group_weight == 1)
+ return cpumask_first(sched_group_span(group));
- /* Skip over this group if it has no CPUs allowed */
- if (!cpumask_intersects(sched_group_span(group),
- p->cpus_ptr))
- continue;
+ /* Traverse only the allowed CPUs */
+ for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
+ struct rq *rq = cpu_rq(i);
- /* Skip over this group if no cookie matched */
- if (!sched_group_cookie_match(cpu_rq(this_cpu), p, group))
+ if (!sched_core_cookie_match(rq, p))
continue;
- local_group = cpumask_test_cpu(this_cpu,
- sched_group_span(group));
-
- if (local_group) {
- sgs = &local_sgs;
- local = group;
- } else {
- sgs = &tmp_sgs;
- }
-
- update_sg_wakeup_stats(sd, group, sgs, p);
-
- if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
- idlest = group;
- idlest_sgs = *sgs;
- }
-
- } while (group = group->next, group != sd->groups);
-
-
- /* There is no idlest group to push tasks to */
- if (!idlest)
- return NULL;
-
- /* The local group has been skipped because of CPU affinity */
- if (!local)
- return idlest;
-
- /*
- * If the local group is idler than the selected idlest group
- * don't try and push the task.
- */
- if (local_sgs.group_type < idlest_sgs.group_type)
- return NULL;
-
- /*
- * If the local group is busier than the selected idlest group
- * try and push the task.
- */
- if (local_sgs.group_type > idlest_sgs.group_type)
- return idlest;
-
- switch (local_sgs.group_type) {
- case group_overloaded:
- case group_fully_busy:
-
- /* Calculate allowed imbalance based on load */
- imbalance = scale_load_down(NICE_0_LOAD) *
- (sd->imbalance_pct-100) / 100;
-
- /*
- * When comparing groups across NUMA domains, it's possible for
- * the local domain to be very lightly loaded relative to the
- * remote domains but "imbalance" skews the comparison making
- * remote CPUs look much more favourable. When considering
- * cross-domain, add imbalance to the load on the remote node
- * and consider staying local.
- */
-
- if ((sd->flags & SD_NUMA) &&
- ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load))
- return NULL;
-
- /*
- * If the local group is less loaded than the selected
- * idlest group don't try and push any tasks.
- */
- if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance))
- return NULL;
-
- if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load)
- return NULL;
- break;
-
- case group_imbalanced:
- case group_asym_packing:
- case group_smt_balance:
- /* Those type are not used in the slow wakeup path */
- return NULL;
-
- case group_misfit_task:
- /* Select group with the highest max capacity */
- if (local->sgc->max_capacity >= idlest->sgc->max_capacity)
- return NULL;
- break;
-
- case group_has_spare:
-#ifdef CONFIG_NUMA
- if (sd->flags & SD_NUMA) {
- int imb_numa_nr = sd->imb_numa_nr;
-#ifdef CONFIG_NUMA_BALANCING
- int idlest_cpu;
- /*
- * If there is spare capacity at NUMA, try to select
- * the preferred node
- */
- if (cpu_to_node(this_cpu) == p->numa_preferred_nid)
- return NULL;
-
- idlest_cpu = cpumask_first(sched_group_span(idlest));
- if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid)
- return idlest;
-#endif /* CONFIG_NUMA_BALANCING */
- /*
- * Otherwise, keep the task close to the wakeup source
- * and improve locality if the number of running tasks
- * would remain below threshold where an imbalance is
- * allowed while accounting for the possibility the
- * task is pinned to a subset of CPUs. If there is a
- * real need of migration, periodic load balance will
- * take care of it.
- */
- if (p->nr_cpus_allowed != NR_CPUS) {
- struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
+ if (sched_idle_cpu(i))
+ return i;
- cpumask_and(cpus, sched_group_span(local), p->cpus_ptr);
- imb_numa_nr = min(cpumask_weight(cpus), sd->imb_numa_nr);
+ if (available_idle_cpu(i)) {
+ struct cpuidle_state *idle = idle_get_state(rq);
+ if (idle && idle->exit_latency < min_exit_latency) {
+ /*
+ * We give priority to a CPU whose idle state
+ * has the smallest exit latency irrespective
+ * of any idle timestamp.
+ */
+ min_exit_latency = idle->exit_latency;
+ latest_idle_timestamp = rq->idle_stamp;
+ shallowest_idle_cpu = i;
+ } else if ((!idle || idle->exit_latency == min_exit_latency) &&
+ rq->idle_stamp > latest_idle_timestamp) {
+ /*
+ * If equal or no active idle state, then
+ * the most recently idled CPU might have
+ * a warmer cache.
+ */
+ latest_idle_timestamp = rq->idle_stamp;
+ shallowest_idle_cpu = i;
}
-
- imbalance = abs(local_sgs.idle_cpus - idlest_sgs.idle_cpus);
- if (!adjust_numa_imbalance(imbalance,
- local_sgs.sum_nr_running + 1,
- imb_numa_nr)) {
- return NULL;
+ } else if (shallowest_idle_cpu == -1) {
+ load = cpu_load(cpu_rq(i));
+ if (load < min_load) {
+ min_load = load;
+ least_loaded_cpu = i;
}
}
-#endif /* CONFIG_NUMA */
-
- /*
- * Select group with highest number of idle CPUs. We could also
- * compare the utilization which is more stable but it can end
- * up that the group has less spare capacity but finally more
- * idle CPUs which means more opportunity to run task.
- */
- if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus)
- return NULL;
- break;
}
- return idlest;
+ return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
}
-static void update_idle_cpu_scan(struct lb_env *env,
- unsigned long sum_util)
+static inline int sched_balance_find_dst_cpu(struct sched_domain *sd, struct task_struct *p,
+ int cpu, int prev_cpu, int sd_flag)
{
- struct sched_domain_shared *sd_share;
- int llc_weight, pct;
- u64 x, y, tmp;
- /*
- * Update the number of CPUs to scan in LLC domain, which could
- * be used as a hint in select_idle_cpu(). The update of sd_share
- * could be expensive because it is within a shared cache line.
- * So the write of this hint only occurs during periodic load
- * balancing, rather than CPU_NEWLY_IDLE, because the latter
- * can fire way more frequently than the former.
- */
- if (!sched_feat(SIS_UTIL) || env->idle == CPU_NEWLY_IDLE)
- return;
-
- llc_weight = per_cpu(sd_llc_size, env->dst_cpu);
- if (env->sd->span_weight != llc_weight)
- return;
+ int new_cpu = cpu;
- sd_share = rcu_dereference(per_cpu(sd_llc_shared, env->dst_cpu));
- if (!sd_share)
- return;
+ if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
+ return prev_cpu;
/*
- * The number of CPUs to search drops as sum_util increases, when
- * sum_util hits 85% or above, the scan stops.
- * The reason to choose 85% as the threshold is because this is the
- * imbalance_pct(117) when a LLC sched group is overloaded.
- *
- * let y = SCHED_CAPACITY_SCALE - p * x^2 [1]
- * and y'= y / SCHED_CAPACITY_SCALE
- *
- * x is the ratio of sum_util compared to the CPU capacity:
- * x = sum_util / (llc_weight * SCHED_CAPACITY_SCALE)
- * y' is the ratio of CPUs to be scanned in the LLC domain,
- * and the number of CPUs to scan is calculated by:
- *
- * nr_scan = llc_weight * y' [2]
- *
- * When x hits the threshold of overloaded, AKA, when
- * x = 100 / pct, y drops to 0. According to [1],
- * p should be SCHED_CAPACITY_SCALE * pct^2 / 10000
- *
- * Scale x by SCHED_CAPACITY_SCALE:
- * x' = sum_util / llc_weight; [3]
- *
- * and finally [1] becomes:
- * y = SCHED_CAPACITY_SCALE -
- * x'^2 * pct^2 / (10000 * SCHED_CAPACITY_SCALE) [4]
- *
+ * We need task's util for cpu_util_without, sync it up to
+ * prev_cpu's last_update_time.
*/
- /* equation [3] */
- x = sum_util;
- do_div(x, llc_weight);
-
- /* equation [4] */
- pct = env->sd->imbalance_pct;
- tmp = x * x * pct * pct;
- do_div(tmp, 10000 * SCHED_CAPACITY_SCALE);
- tmp = min_t(long, tmp, SCHED_CAPACITY_SCALE);
- y = SCHED_CAPACITY_SCALE - tmp;
-
- /* equation [2] */
- y *= llc_weight;
- do_div(y, SCHED_CAPACITY_SCALE);
- if ((int)y != sd_share->nr_idle_scan)
- WRITE_ONCE(sd_share->nr_idle_scan, (int)y);
-}
-
-/**
- * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
- * @env: The load balancing environment.
- * @sds: variable to hold the statistics for this sched_domain.
- */
-
-static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
-{
- struct sched_group *sg = env->sd->groups;
- struct sg_lb_stats *local = &sds->local_stat;
- struct sg_lb_stats tmp_sgs;
- unsigned long sum_util = 0;
- bool sg_overloaded = 0, sg_overutilized = 0;
+ if (!(sd_flag & SD_BALANCE_FORK))
+ sync_entity_load_avg(&p->se);
- do {
- struct sg_lb_stats *sgs = &tmp_sgs;
- int local_group;
+ while (sd) {
+ struct sched_group *group;
+ struct sched_domain *tmp;
+ int weight;
- local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
- if (local_group) {
- sds->local = sg;
- sgs = local;
+ if (!(sd->flags & sd_flag)) {
+ sd = sd->child;
+ continue;
+ }
- if (env->idle != CPU_NEWLY_IDLE ||
- time_after_eq(jiffies, sg->sgc->next_update))
- update_group_capacity(env->sd, env->dst_cpu);
+ group = sched_balance_find_dst_group(sd, p, cpu);
+ if (!group) {
+ sd = sd->child;
+ continue;
}
- update_sg_lb_stats(env, sds, sg, sgs, &sg_overloaded, &sg_overutilized);
+ new_cpu = sched_balance_find_dst_group_cpu(group, p, cpu);
+ if (new_cpu == cpu) {
+ /* Now try balancing at a lower domain level of 'cpu': */
+ sd = sd->child;
+ continue;
+ }
- if (!local_group && update_sd_pick_busiest(env, sds, sg, sgs)) {
- sds->busiest = sg;
- sds->busiest_stat = *sgs;
+ /* Now try balancing at a lower domain level of 'new_cpu': */
+ cpu = new_cpu;
+ weight = sd->span_weight;
+ sd = NULL;
+ for_each_domain(cpu, tmp) {
+ if (weight <= tmp->span_weight)
+ break;
+ if (tmp->flags & sd_flag)
+ sd = tmp;
}
+ }
+
+ return new_cpu;
+}
- /* Now, start updating sd_lb_stats */
- sds->total_load += sgs->group_load;
- sds->total_capacity += sgs->group_capacity;
+static inline int __select_idle_cpu(int cpu, struct task_struct *p)
+{
+ if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) &&
+ sched_cpu_cookie_match(cpu_rq(cpu), p))
+ return cpu;
- sum_util += sgs->group_util;
- sg = sg->next;
- } while (sg != env->sd->groups);
+ return -1;
+}
- /*
- * Indicate that the child domain of the busiest group prefers tasks
- * go to a child's sibling domains first. NB the flags of a sched group
- * are those of the child domain.
- */
- if (sds->busiest)
- sds->prefer_sibling = !!(sds->busiest->flags & SD_PREFER_SIBLING);
+#ifdef CONFIG_SCHED_SMT
+DEFINE_STATIC_KEY_FALSE(sched_smt_present);
+EXPORT_SYMBOL_GPL(sched_smt_present);
+static inline void set_idle_cores(int cpu, int val)
+{
+ struct sched_domain_shared *sds;
- if (env->sd->flags & SD_NUMA)
- env->fbq_type = fbq_classify_group(&sds->busiest_stat);
+ sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
+ if (sds)
+ WRITE_ONCE(sds->has_idle_cores, val);
+}
- if (!env->sd->parent) {
- /* update overload indicator if we are at root domain */
- set_rd_overloaded(env->dst_rq->rd, sg_overloaded);
+static inline bool test_idle_cores(int cpu)
+{
+ struct sched_domain_shared *sds;
- /* Update over-utilization (tipping point, U >= 0) indicator */
- set_rd_overutilized(env->dst_rq->rd, sg_overloaded);
- } else if (sg_overutilized) {
- set_rd_overutilized(env->dst_rq->rd, sg_overutilized);
- }
+ sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
+ if (sds)
+ return READ_ONCE(sds->has_idle_cores);
- update_idle_cpu_scan(env, sum_util);
+ return false;
}
-/**
- * calculate_imbalance - Calculate the amount of imbalance present within the
- * groups of a given sched_domain during load balance.
- * @env: load balance environment
- * @sds: statistics of the sched_domain whose imbalance is to be calculated.
+/*
+ * Scans the local SMT mask to see if the entire core is idle, and records this
+ * information in sd_llc_shared->has_idle_cores.
+ *
+ * Since SMT siblings share all cache levels, inspecting this limited remote
+ * state should be fairly cheap.
*/
-static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
+void __update_idle_core(struct rq *rq)
{
- struct sg_lb_stats *local, *busiest;
-
- local = &sds->local_stat;
- busiest = &sds->busiest_stat;
+ int core = cpu_of(rq);
+ int cpu;
- if (busiest->group_type == group_misfit_task) {
- if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
- /* Set imbalance to allow misfit tasks to be balanced. */
- env->migration_type = migrate_misfit;
- env->imbalance = 1;
- } else {
- /*
- * Set load imbalance to allow moving task from cpu
- * with reduced capacity.
- */
- env->migration_type = migrate_load;
- env->imbalance = busiest->group_misfit_task_load;
- }
- return;
- }
+ rcu_read_lock();
+ if (test_idle_cores(core))
+ goto unlock;
- if (busiest->group_type == group_asym_packing) {
- /*
- * In case of asym capacity, we will try to migrate all load to
- * the preferred CPU.
- */
- env->migration_type = migrate_task;
- env->imbalance = busiest->sum_h_nr_running;
- return;
- }
+ for_each_cpu(cpu, cpu_smt_mask(core)) {
+ if (cpu == core)
+ continue;
- if (busiest->group_type == group_smt_balance) {
- /* Reduce number of tasks sharing CPU capacity */
- env->migration_type = migrate_task;
- env->imbalance = 1;
- return;
+ if (!available_idle_cpu(cpu))
+ goto unlock;
}
- if (busiest->group_type == group_imbalanced) {
- /*
- * In the group_imb case we cannot rely on group-wide averages
- * to ensure CPU-load equilibrium, try to move any task to fix
- * the imbalance. The next load balance will take care of
- * balancing back the system.
- */
- env->migration_type = migrate_task;
- env->imbalance = 1;
- return;
- }
+ set_idle_cores(core, 1);
+unlock:
+ rcu_read_unlock();
+}
- /*
- * Try to use spare capacity of local group without overloading it or
- * emptying busiest.
- */
- if (local->group_type == group_has_spare) {
- if ((busiest->group_type > group_fully_busy) &&
- !(env->sd->flags & SD_SHARE_LLC)) {
- /*
- * If busiest is overloaded, try to fill spare
- * capacity. This might end up creating spare capacity
- * in busiest or busiest still being overloaded but
- * there is no simple way to directly compute the
- * amount of load to migrate in order to balance the
- * system.
- */
- env->migration_type = migrate_util;
- env->imbalance = max(local->group_capacity, local->group_util) -
- local->group_util;
+/*
+ * Scan the entire LLC domain for idle cores; this dynamically switches off if
+ * there are no idle cores left in the system; tracked through
+ * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
+ */
+static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
+{
+ bool idle = true;
+ int cpu;
- /*
- * In some cases, the group's utilization is max or even
- * higher than capacity because of migrations but the
- * local CPU is (newly) idle. There is at least one
- * waiting task in this overloaded busiest group. Let's
- * try to pull it.
- */
- if (env->idle && env->imbalance == 0) {
- env->migration_type = migrate_task;
- env->imbalance = 1;
+ for_each_cpu(cpu, cpu_smt_mask(core)) {
+ if (!available_idle_cpu(cpu)) {
+ idle = false;
+ if (*idle_cpu == -1) {
+ if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, cpus)) {
+ *idle_cpu = cpu;
+ break;
+ }
+ continue;
}
-
- return;
- }
-
- if (busiest->group_weight == 1 || sds->prefer_sibling) {
- /*
- * When prefer sibling, evenly spread running tasks on
- * groups.
- */
- env->migration_type = migrate_task;
- env->imbalance = sibling_imbalance(env, sds, busiest, local);
- } else {
-
- /*
- * If there is no overload, we just want to even the number of
- * idle CPUs.
- */
- env->migration_type = migrate_task;
- env->imbalance = max_t(long, 0,
- (local->idle_cpus - busiest->idle_cpus));
- }
-
-#ifdef CONFIG_NUMA
- /* Consider allowing a small imbalance between NUMA groups */
- if (env->sd->flags & SD_NUMA) {
- env->imbalance = adjust_numa_imbalance(env->imbalance,
- local->sum_nr_running + 1,
- env->sd->imb_numa_nr);
+ break;
}
-#endif
-
- /* Number of tasks to move to restore balance */
- env->imbalance >>= 1;
-
- return;
+ if (*idle_cpu == -1 && cpumask_test_cpu(cpu, cpus))
+ *idle_cpu = cpu;
}
- /*
- * Local is fully busy but has to take more load to relieve the
- * busiest group
- */
- if (local->group_type < group_overloaded) {
- /*
- * Local will become overloaded so the avg_load metrics are
- * finally needed.
- */
-
- local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) /
- local->group_capacity;
+ if (idle)
+ return core;
- /*
- * If the local group is more loaded than the selected
- * busiest group don't try to pull any tasks.
- */
- if (local->avg_load >= busiest->avg_load) {
- env->imbalance = 0;
- return;
- }
+ cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
+ return -1;
+}
- sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
- sds->total_capacity;
+/*
+ * Scan the local SMT mask for idle CPUs.
+ */
+static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
+{
+ int cpu;
+ for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
+ if (cpu == target)
+ continue;
/*
- * If the local group is more loaded than the average system
- * load, don't try to pull any tasks.
+ * Check if the CPU is in the LLC scheduling domain of @target.
+ * Due to isolcpus, there is no guarantee that all the siblings are in the domain.
*/
- if (local->avg_load >= sds->avg_load) {
- env->imbalance = 0;
- return;
- }
-
+ if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
+ continue;
+ if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
+ return cpu;
}
- /*
- * Both group are or will become overloaded and we're trying to get all
- * the CPUs to the average_load, so we don't want to push ourselves
- * above the average load, nor do we wish to reduce the max loaded CPU
- * below the average load. At the same time, we also don't want to
- * reduce the group load below the group capacity. Thus we look for
- * the minimum possible imbalance.
- */
- env->migration_type = migrate_load;
- env->imbalance = min(
- (busiest->avg_load - sds->avg_load) * busiest->group_capacity,
- (sds->avg_load - local->avg_load) * local->group_capacity
- ) / SCHED_CAPACITY_SCALE;
+ return -1;
}
-/******* sched_balance_find_src_group() helpers end here *********************/
-
-/*
- * Decision matrix according to the local and busiest group type:
- *
- * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
- * has_spare nr_idle balanced N/A N/A balanced balanced
- * fully_busy nr_idle nr_idle N/A N/A balanced balanced
- * misfit_task force N/A N/A N/A N/A N/A
- * asym_packing force force N/A N/A force force
- * imbalanced force force N/A N/A force force
- * overloaded force force N/A N/A force avg_load
- *
- * N/A : Not Applicable because already filtered while updating
- * statistics.
- * balanced : The system is balanced for these 2 groups.
- * force : Calculate the imbalance as load migration is probably needed.
- * avg_load : Only if imbalance is significant enough.
- * nr_idle : dst_cpu is not busy and the number of idle CPUs is quite
- * different in groups.
- */
+#else /* CONFIG_SCHED_SMT */
-/**
- * sched_balance_find_src_group - Returns the busiest group within the sched_domain
- * if there is an imbalance.
- * @env: The load balancing environment.
- *
- * Also calculates the amount of runnable load which should be moved
- * to restore balance.
- *
- * Return: - The busiest group if imbalance exists.
- */
-static struct sched_group *sched_balance_find_src_group(struct lb_env *env)
+static inline void set_idle_cores(int cpu, int val)
{
- struct sg_lb_stats *local, *busiest;
- struct sd_lb_stats sds;
-
- init_sd_lb_stats(&sds);
-
- /*
- * Compute the various statistics relevant for load balancing at
- * this level.
- */
- update_sd_lb_stats(env, &sds);
-
- /* There is no busy sibling group to pull tasks from */
- if (!sds.busiest)
- goto out_balanced;
-
- busiest = &sds.busiest_stat;
-
- /* Misfit tasks should be dealt with regardless of the avg load */
- if (busiest->group_type == group_misfit_task)
- goto force_balance;
-
- if (!is_rd_overutilized(env->dst_rq->rd) &&
- rcu_dereference(env->dst_rq->rd->pd))
- goto out_balanced;
+}
- /* ASYM feature bypasses nice load balance check */
- if (busiest->group_type == group_asym_packing)
- goto force_balance;
+static inline bool test_idle_cores(int cpu)
+{
+ return false;
+}
- /*
- * If the busiest group is imbalanced the below checks don't
- * work because they assume all things are equal, which typically
- * isn't true due to cpus_ptr constraints and the like.
- */
- if (busiest->group_type == group_imbalanced)
- goto force_balance;
+static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
+{
+ return __select_idle_cpu(core, p);
+}
- local = &sds.local_stat;
- /*
- * If the local group is busier than the selected busiest group
- * don't try and pull any tasks.
- */
- if (local->group_type > busiest->group_type)
- goto out_balanced;
+static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
+{
+ return -1;
+}
- /*
- * When groups are overloaded, use the avg_load to ensure fairness
- * between tasks.
- */
- if (local->group_type == group_overloaded) {
- /*
- * If the local group is more loaded than the selected
- * busiest group don't try to pull any tasks.
- */
- if (local->avg_load >= busiest->avg_load)
- goto out_balanced;
+#endif /* CONFIG_SCHED_SMT */
- /* XXX broken for overlapping NUMA groups */
- sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) /
- sds.total_capacity;
+/*
+ * Scan the LLC domain for idle CPUs; this is dynamically regulated by
+ * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
+ * average idle time for this rq (as found in rq->avg_idle).
+ */
+static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool has_idle_core, int target)
+{
+ struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
+ int i, cpu, idle_cpu = -1, nr = INT_MAX;
+ struct sched_domain_shared *sd_share;
- /*
- * Don't pull any tasks if this group is already above the
- * domain average load.
- */
- if (local->avg_load >= sds.avg_load)
- goto out_balanced;
+ cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
- /*
- * If the busiest group is more loaded, use imbalance_pct to be
- * conservative.
- */
- if (100 * busiest->avg_load <=
- env->sd->imbalance_pct * local->avg_load)
- goto out_balanced;
+ if (sched_feat(SIS_UTIL)) {
+ sd_share = rcu_dereference(per_cpu(sd_llc_shared, target));
+ if (sd_share) {
+ /* because !--nr is the condition to stop scan */
+ nr = READ_ONCE(sd_share->nr_idle_scan) + 1;
+ /* overloaded LLC is unlikely to have idle cpu/core */
+ if (nr == 1)
+ return -1;
+ }
}
- /*
- * Try to move all excess tasks to a sibling domain of the busiest
- * group's child domain.
- */
- if (sds.prefer_sibling && local->group_type == group_has_spare &&
- sibling_imbalance(env, &sds, busiest, local) > 1)
- goto force_balance;
+ if (static_branch_unlikely(&sched_cluster_active)) {
+ struct sched_group *sg = sd->groups;
- if (busiest->group_type != group_overloaded) {
- if (!env->idle) {
- /*
- * If the busiest group is not overloaded (and as a
- * result the local one too) but this CPU is already
- * busy, let another idle CPU try to pull task.
- */
- goto out_balanced;
- }
+ if (sg->flags & SD_CLUSTER) {
+ for_each_cpu_wrap(cpu, sched_group_span(sg), target + 1) {
+ if (!cpumask_test_cpu(cpu, cpus))
+ continue;
- if (busiest->group_type == group_smt_balance &&
- smt_vs_nonsmt_groups(sds.local, sds.busiest)) {
- /* Let non SMT CPU pull from SMT CPU sharing with sibling */
- goto force_balance;
+ if (has_idle_core) {
+ i = select_idle_core(p, cpu, cpus, &idle_cpu);
+ if ((unsigned int)i < nr_cpumask_bits)
+ return i;
+ } else {
+ if (--nr <= 0)
+ return -1;
+ idle_cpu = __select_idle_cpu(cpu, p);
+ if ((unsigned int)idle_cpu < nr_cpumask_bits)
+ return idle_cpu;
+ }
+ }
+ cpumask_andnot(cpus, cpus, sched_group_span(sg));
}
+ }
- if (busiest->group_weight > 1 &&
- local->idle_cpus <= (busiest->idle_cpus + 1)) {
- /*
- * If the busiest group is not overloaded
- * and there is no imbalance between this and busiest
- * group wrt idle CPUs, it is balanced. The imbalance
- * becomes significant if the diff is greater than 1
- * otherwise we might end up to just move the imbalance
- * on another group. Of course this applies only if
- * there is more than 1 CPU per group.
- */
- goto out_balanced;
- }
+ for_each_cpu_wrap(cpu, cpus, target + 1) {
+ if (has_idle_core) {
+ i = select_idle_core(p, cpu, cpus, &idle_cpu);
+ if ((unsigned int)i < nr_cpumask_bits)
+ return i;
- if (busiest->sum_h_nr_running == 1) {
- /*
- * busiest doesn't have any tasks waiting to run
- */
- goto out_balanced;
+ } else {
+ if (--nr <= 0)
+ return -1;
+ idle_cpu = __select_idle_cpu(cpu, p);
+ if ((unsigned int)idle_cpu < nr_cpumask_bits)
+ break;
}
}
-force_balance:
- /* Looks like there is an imbalance. Compute it */
- calculate_imbalance(env, &sds);
- return env->imbalance ? sds.busiest : NULL;
+ if (has_idle_core)
+ set_idle_cores(target, false);
-out_balanced:
- env->imbalance = 0;
- return NULL;
+ return idle_cpu;
}
/*
- * sched_balance_find_src_rq - find the busiest runqueue among the CPUs in the group.
+ * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
+ * the task fits. If no CPU is big enough, but there are idle ones, try to
+ * maximize capacity.
*/
-static struct rq *sched_balance_find_src_rq(struct lb_env *env,
- struct sched_group *group)
+static int
+select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
{
- struct rq *busiest = NULL, *rq;
- unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
- unsigned int busiest_nr = 0;
- int i;
-
- for_each_cpu_and(i, sched_group_span(group), env->cpus) {
- unsigned long capacity, load, util;
- unsigned int nr_running;
- enum fbq_type rt;
-
- rq = cpu_rq(i);
- rt = fbq_classify_rq(rq);
+ unsigned long task_util, util_min, util_max, best_cap = 0;
+ int fits, best_fits = 0;
+ int cpu, best_cpu = -1;
+ struct cpumask *cpus;
- /*
- * We classify groups/runqueues into three groups:
- * - regular: there are !numa tasks
- * - remote: there are numa tasks that run on the 'wrong' node
- * - all: there is no distinction
- *
- * In order to avoid migrating ideally placed numa tasks,
- * ignore those when there's better options.
- *
- * If we ignore the actual busiest queue to migrate another
- * task, the next balance pass can still reduce the busiest
- * queue by moving tasks around inside the node.
- *
- * If we cannot move enough load due to this classification
- * the next pass will adjust the group classification and
- * allow migration of more tasks.
- *
- * Both cases only affect the total convergence complexity.
- */
- if (rt > env->fbq_type)
- continue;
+ cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
+ cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+
+ task_util = task_util_est(p);
+ util_min = uclamp_eff_value(p, UCLAMP_MIN);
+ util_max = uclamp_eff_value(p, UCLAMP_MAX);
+
+ for_each_cpu_wrap(cpu, cpus, target) {
+ unsigned long cpu_cap = capacity_of(cpu);
- nr_running = rq->cfs.h_nr_running;
- if (!nr_running)
+ if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
continue;
- capacity = capacity_of(i);
+ fits = util_fits_cpu(task_util, util_min, util_max, cpu);
+ /* This CPU fits with all requirements */
+ if (fits > 0)
+ return cpu;
/*
- * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
- * eventually lead to active_balancing high->low capacity.
- * Higher per-CPU capacity is considered better than balancing
- * average load.
+ * Only the min performance hint (i.e. uclamp_min) doesn't fit.
+ * Look for the CPU with best capacity.
*/
- if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
- !capacity_greater(capacity_of(env->dst_cpu), capacity) &&
- nr_running == 1)
- continue;
+ else if (fits < 0)
+ cpu_cap = arch_scale_cpu_capacity(cpu) - thermal_load_avg(cpu_rq(cpu));
/*
- * Make sure we only pull tasks from a CPU of lower priority
- * when balancing between SMT siblings.
- *
- * If balancing between cores, let lower priority CPUs help
- * SMT cores with more than one busy sibling.
+ * First, select CPU which fits better (-1 being better than 0).
+ * Then, select the one with best capacity at same level.
*/
- if (sched_asym(env->sd, i, env->dst_cpu) && nr_running == 1)
- continue;
-
- switch (env->migration_type) {
- case migrate_load:
- /*
- * When comparing with load imbalance, use cpu_load()
- * which is not scaled with the CPU capacity.
- */
- load = cpu_load(rq);
-
- if (nr_running == 1 && load > env->imbalance &&
- !check_cpu_capacity(rq, env->sd))
- break;
-
- /*
- * For the load comparisons with the other CPUs,
- * consider the cpu_load() scaled with the CPU
- * capacity, so that the load can be moved away
- * from the CPU that is potentially running at a
- * lower capacity.
- *
- * Thus we're looking for max(load_i / capacity_i),
- * crosswise multiplication to rid ourselves of the
- * division works out to:
- * load_i * capacity_j > load_j * capacity_i;
- * where j is our previous maximum.
- */
- if (load * busiest_capacity > busiest_load * capacity) {
- busiest_load = load;
- busiest_capacity = capacity;
- busiest = rq;
- }
- break;
-
- case migrate_util:
- util = cpu_util_cfs_boost(i);
-
- /*
- * Don't try to pull utilization from a CPU with one
- * running task. Whatever its utilization, we will fail
- * detach the task.
- */
- if (nr_running <= 1)
- continue;
-
- if (busiest_util < util) {
- busiest_util = util;
- busiest = rq;
- }
- break;
-
- case migrate_task:
- if (busiest_nr < nr_running) {
- busiest_nr = nr_running;
- busiest = rq;
- }
- break;
-
- case migrate_misfit:
- /*
- * For ASYM_CPUCAPACITY domains with misfit tasks we
- * simply seek the "biggest" misfit task.
- */
- if (rq->misfit_task_load > busiest_load) {
- busiest_load = rq->misfit_task_load;
- busiest = rq;
- }
-
- break;
-
+ if ((fits < best_fits) ||
+ ((fits == best_fits) && (cpu_cap > best_cap))) {
+ best_cap = cpu_cap;
+ best_cpu = cpu;
+ best_fits = fits;
}
}
- return busiest;
+ return best_cpu;
+}
+
+static inline bool asym_fits_cpu(unsigned long util,
+ unsigned long util_min,
+ unsigned long util_max,
+ int cpu)
+{
+ if (sched_asym_cpucap_active())
+ /*
+ * Return true only if the cpu fully fits the task requirements
+ * which include the utilization and the performance hints.
+ */
+ return (util_fits_cpu(util, util_min, util_max, cpu) > 0);
+
+ return true;
}
/*
- * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
- * so long as it is large enough.
+ * Try and locate an idle core/thread in the LLC cache domain.
*/
-#define MAX_PINNED_INTERVAL 512
-
-static inline bool
-asym_active_balance(struct lb_env *env)
+static int select_idle_sibling(struct task_struct *p, int prev, int target)
{
+ bool has_idle_core = false;
+ struct sched_domain *sd;
+ unsigned long task_util, util_min, util_max;
+ int i, recent_used_cpu, prev_aff = -1;
+
/*
- * ASYM_PACKING needs to force migrate tasks from busy but lower
- * priority CPUs in order to pack all tasks in the highest priority
- * CPUs. When done between cores, do it only if the whole core if the
- * whole core is idle.
- *
- * If @env::src_cpu is an SMT core with busy siblings, let
- * the lower priority @env::dst_cpu help it. Do not follow
- * CPU priority.
+ * On asymmetric system, update task utilization because we will check
+ * that the task fits with CPU's capacity.
*/
- return env->idle && sched_use_asym_prio(env->sd, env->dst_cpu) &&
- (sched_asym_prefer(env->dst_cpu, env->src_cpu) ||
- !sched_use_asym_prio(env->sd, env->src_cpu));
-}
-
-static inline bool
-imbalanced_active_balance(struct lb_env *env)
-{
- struct sched_domain *sd = env->sd;
+ if (sched_asym_cpucap_active()) {
+ sync_entity_load_avg(&p->se);
+ task_util = task_util_est(p);
+ util_min = uclamp_eff_value(p, UCLAMP_MIN);
+ util_max = uclamp_eff_value(p, UCLAMP_MAX);
+ }
/*
- * The imbalanced case includes the case of pinned tasks preventing a fair
- * distribution of the load on the system but also the even distribution of the
- * threads on a system with spare capacity
+ * per-cpu select_rq_mask usage
*/
- if ((env->migration_type == migrate_task) &&
- (sd->nr_balance_failed > sd->cache_nice_tries+2))
- return 1;
+ lockdep_assert_irqs_disabled();
- return 0;
-}
+ if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
+ asym_fits_cpu(task_util, util_min, util_max, target))
+ return target;
-static int need_active_balance(struct lb_env *env)
-{
- struct sched_domain *sd = env->sd;
+ /*
+ * If the previous CPU is cache affine and idle, don't be stupid:
+ */
+ if (prev != target && cpus_share_cache(prev, target) &&
+ (available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
+ asym_fits_cpu(task_util, util_min, util_max, prev)) {
- if (asym_active_balance(env))
- return 1;
+ if (!static_branch_unlikely(&sched_cluster_active) ||
+ cpus_share_resources(prev, target))
+ return prev;
- if (imbalanced_active_balance(env))
- return 1;
+ prev_aff = prev;
+ }
/*
- * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
- * It's worth migrating the task if the src_cpu's capacity is reduced
- * because of other sched_class or IRQs if more capacity stays
- * available on dst_cpu.
+ * Allow a per-cpu kthread to stack with the wakee if the
+ * kworker thread and the tasks previous CPUs are the same.
+ * The assumption is that the wakee queued work for the
+ * per-cpu kthread that is now complete and the wakeup is
+ * essentially a sync wakeup. An obvious example of this
+ * pattern is IO completions.
*/
- if (env->idle &&
- (env->src_rq->cfs.h_nr_running == 1)) {
- if ((check_cpu_capacity(env->src_rq, sd)) &&
- (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
- return 1;
+ if (is_per_cpu_kthread(current) &&
+ in_task() &&
+ prev == smp_processor_id() &&
+ this_rq()->nr_running <= 1 &&
+ asym_fits_cpu(task_util, util_min, util_max, prev)) {
+ return prev;
}
- if (env->migration_type == migrate_misfit)
- return 1;
-
- return 0;
-}
-
-static int active_load_balance_cpu_stop(void *data);
+ /* Check a recently used CPU as a potential idle candidate: */
+ recent_used_cpu = p->recent_used_cpu;
+ p->recent_used_cpu = prev;
+ if (recent_used_cpu != prev &&
+ recent_used_cpu != target &&
+ cpus_share_cache(recent_used_cpu, target) &&
+ (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
+ cpumask_test_cpu(recent_used_cpu, p->cpus_ptr) &&
+ asym_fits_cpu(task_util, util_min, util_max, recent_used_cpu)) {
-static int should_we_balance(struct lb_env *env)
-{
- struct cpumask *swb_cpus = this_cpu_cpumask_var_ptr(should_we_balance_tmpmask);
- struct sched_group *sg = env->sd->groups;
- int cpu, idle_smt = -1;
+ if (!static_branch_unlikely(&sched_cluster_active) ||
+ cpus_share_resources(recent_used_cpu, target))
+ return recent_used_cpu;
- /*
- * Ensure the balancing environment is consistent; can happen
- * when the softirq triggers 'during' hotplug.
- */
- if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
- return 0;
+ } else {
+ recent_used_cpu = -1;
+ }
/*
- * In the newly idle case, we will allow all the CPUs
- * to do the newly idle load balance.
- *
- * However, we bail out if we already have tasks or a wakeup pending,
- * to optimize wakeup latency.
+ * For asymmetric CPU capacity systems, our domain of interest is
+ * sd_asym_cpucapacity rather than sd_llc.
*/
- if (env->idle == CPU_NEWLY_IDLE) {
- if (env->dst_rq->nr_running > 0 || env->dst_rq->ttwu_pending)
- return 0;
- return 1;
- }
-
- cpumask_copy(swb_cpus, group_balance_mask(sg));
- /* Try to find first idle CPU */
- for_each_cpu_and(cpu, swb_cpus, env->cpus) {
- if (!idle_cpu(cpu))
- continue;
-
+ if (sched_asym_cpucap_active()) {
+ sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
/*
- * Don't balance to idle SMT in busy core right away when
- * balancing cores, but remember the first idle SMT CPU for
- * later consideration. Find CPU on an idle core first.
+ * On an asymmetric CPU capacity system where an exclusive
+ * cpuset defines a symmetric island (i.e. one unique
+ * capacity_orig value through the cpuset), the key will be set
+ * but the CPUs within that cpuset will not have a domain with
+ * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
+ * capacity path.
*/
- if (!(env->sd->flags & SD_SHARE_CPUCAPACITY) && !is_core_idle(cpu)) {
- if (idle_smt == -1)
- idle_smt = cpu;
- /*
- * If the core is not idle, and first SMT sibling which is
- * idle has been found, then its not needed to check other
- * SMT siblings for idleness:
- */
-#ifdef CONFIG_SCHED_SMT
- cpumask_andnot(swb_cpus, swb_cpus, cpu_smt_mask(cpu));
-#endif
- continue;
+ if (sd) {
+ i = select_idle_capacity(p, sd, target);
+ return ((unsigned)i < nr_cpumask_bits) ? i : target;
}
-
- /*
- * Are we the first idle core in a non-SMT domain or higher,
- * or the first idle CPU in a SMT domain?
- */
- return cpu == env->dst_cpu;
}
- /* Are we the first idle CPU with busy siblings? */
- if (idle_smt != -1)
- return idle_smt == env->dst_cpu;
+ sd = rcu_dereference(per_cpu(sd_llc, target));
+ if (!sd)
+ return target;
- /* Are we the first CPU of this group ? */
- return group_balance_cpu(sg) == env->dst_cpu;
-}
+ if (sched_smt_active()) {
+ has_idle_core = test_idle_cores(target);
-/*
- * Check this_cpu to ensure it is balanced within domain. Attempt to move
- * tasks if there is an imbalance.
- */
-static int sched_balance_rq(int this_cpu, struct rq *this_rq,
- struct sched_domain *sd, enum cpu_idle_type idle,
- int *continue_balancing)
-{
- int ld_moved, cur_ld_moved, active_balance = 0;
- struct sched_domain *sd_parent = sd->parent;
- struct sched_group *group;
- struct rq *busiest;
- struct rq_flags rf;
- struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
- struct lb_env env = {
- .sd = sd,
- .dst_cpu = this_cpu,
- .dst_rq = this_rq,
- .dst_grpmask = group_balance_mask(sd->groups),
- .idle = idle,
- .loop_break = SCHED_NR_MIGRATE_BREAK,
- .cpus = cpus,
- .fbq_type = all,
- .tasks = LIST_HEAD_INIT(env.tasks),
- };
+ if (!has_idle_core && cpus_share_cache(prev, target)) {
+ i = select_idle_smt(p, sd, prev);
+ if ((unsigned int)i < nr_cpumask_bits)
+ return i;
+ }
+ }
- cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
+ i = select_idle_cpu(p, sd, has_idle_core, target);
+ if ((unsigned)i < nr_cpumask_bits)
+ return i;
- schedstat_inc(sd->lb_count[idle]);
+ /*
+ * For cluster machines which have lower sharing cache like L2 or
+ * LLC Tag, we tend to find an idle CPU in the target's cluster
+ * first. But prev_cpu or recent_used_cpu may also be a good candidate,
+ * use them if possible when no idle CPU found in select_idle_cpu().
+ */
+ if ((unsigned int)prev_aff < nr_cpumask_bits)
+ return prev_aff;
+ if ((unsigned int)recent_used_cpu < nr_cpumask_bits)
+ return recent_used_cpu;
-redo:
- if (!should_we_balance(&env)) {
- *continue_balancing = 0;
- goto out_balanced;
- }
+ return target;
+}
- group = sched_balance_find_src_group(&env);
- if (!group) {
- schedstat_inc(sd->lb_nobusyg[idle]);
- goto out_balanced;
- }
+/**
+ * cpu_util() - Estimates the amount of CPU capacity used by CFS tasks.
+ * @cpu: the CPU to get the utilization for
+ * @p: task for which the CPU utilization should be predicted or NULL
+ * @dst_cpu: CPU @p migrates to, -1 if @p moves from @cpu or @p == NULL
+ * @boost: 1 to enable boosting, otherwise 0
+ *
+ * The unit of the return value must be the same as the one of CPU capacity
+ * so that CPU utilization can be compared with CPU capacity.
+ *
+ * CPU utilization is the sum of running time of runnable tasks plus the
+ * recent utilization of currently non-runnable tasks on that CPU.
+ * It represents the amount of CPU capacity currently used by CFS tasks in
+ * the range [0..max CPU capacity] with max CPU capacity being the CPU
+ * capacity at f_max.
+ *
+ * The estimated CPU utilization is defined as the maximum between CPU
+ * utilization and sum of the estimated utilization of the currently
+ * runnable tasks on that CPU. It preserves a utilization "snapshot" of
+ * previously-executed tasks, which helps better deduce how busy a CPU will
+ * be when a long-sleeping task wakes up. The contribution to CPU utilization
+ * of such a task would be significantly decayed at this point of time.
+ *
+ * Boosted CPU utilization is defined as max(CPU runnable, CPU utilization).
+ * CPU contention for CFS tasks can be detected by CPU runnable > CPU
+ * utilization. Boosting is implemented in cpu_util() so that internal
+ * users (e.g. EAS) can use it next to external users (e.g. schedutil),
+ * latter via cpu_util_cfs_boost().
+ *
+ * CPU utilization can be higher than the current CPU capacity
+ * (f_curr/f_max * max CPU capacity) or even the max CPU capacity because
+ * of rounding errors as well as task migrations or wakeups of new tasks.
+ * CPU utilization has to be capped to fit into the [0..max CPU capacity]
+ * range. Otherwise a group of CPUs (CPU0 util = 121% + CPU1 util = 80%)
+ * could be seen as over-utilized even though CPU1 has 20% of spare CPU
+ * capacity. CPU utilization is allowed to overshoot current CPU capacity
+ * though since this is useful for predicting the CPU capacity required
+ * after task migrations (scheduler-driven DVFS).
+ *
+ * Return: (Boosted) (estimated) utilization for the specified CPU.
+ */
+static unsigned long
+cpu_util(int cpu, struct task_struct *p, int dst_cpu, int boost)
+{
+ struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
+ unsigned long util = READ_ONCE(cfs_rq->avg.util_avg);
+ unsigned long runnable;
- busiest = sched_balance_find_src_rq(&env, group);
- if (!busiest) {
- schedstat_inc(sd->lb_nobusyq[idle]);
- goto out_balanced;
+ if (boost) {
+ runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
+ util = max(util, runnable);
}
- WARN_ON_ONCE(busiest == env.dst_rq);
+ /*
+ * If @dst_cpu is -1 or @p migrates from @cpu to @dst_cpu remove its
+ * contribution. If @p migrates from another CPU to @cpu add its
+ * contribution. In all the other cases @cpu is not impacted by the
+ * migration so its util_avg is already correct.
+ */
+ if (p && task_cpu(p) == cpu && dst_cpu != cpu)
+ lsub_positive(&util, task_util(p));
+ else if (p && task_cpu(p) != cpu && dst_cpu == cpu)
+ util += task_util(p);
- schedstat_add(sd->lb_imbalance[idle], env.imbalance);
+ if (sched_feat(UTIL_EST)) {
+ unsigned long util_est;
- env.src_cpu = busiest->cpu;
- env.src_rq = busiest;
+ util_est = READ_ONCE(cfs_rq->avg.util_est);
- ld_moved = 0;
- /* Clear this flag as soon as we find a pullable task */
- env.flags |= LBF_ALL_PINNED;
- if (busiest->nr_running > 1) {
/*
- * Attempt to move tasks. If sched_balance_find_src_group has found
- * an imbalance but busiest->nr_running <= 1, the group is
- * still unbalanced. ld_moved simply stays zero, so it is
- * correctly treated as an imbalance.
+ * During wake-up @p isn't enqueued yet and doesn't contribute
+ * to any cpu_rq(cpu)->cfs.avg.util_est.
+ * If @dst_cpu == @cpu add it to "simulate" cpu_util after @p
+ * has been enqueued.
+ *
+ * During exec (@dst_cpu = -1) @p is enqueued and does
+ * contribute to cpu_rq(cpu)->cfs.util_est.
+ * Remove it to "simulate" cpu_util without @p's contribution.
+ *
+ * Despite the task_on_rq_queued(@p) check there is still a
+ * small window for a possible race when an exec
+ * select_task_rq_fair() races with LB's detach_task().
+ *
+ * detach_task()
+ * deactivate_task()
+ * p->on_rq = TASK_ON_RQ_MIGRATING;
+ * -------------------------------- A
+ * dequeue_task() \
+ * dequeue_task_fair() + Race Time
+ * util_est_dequeue() /
+ * -------------------------------- B
+ *
+ * The additional check "current == p" is required to further
+ * reduce the race window.
*/
- env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
-
-more_balance:
- rq_lock_irqsave(busiest, &rf);
- update_rq_clock(busiest);
+ if (dst_cpu == cpu)
+ util_est += _task_util_est(p);
+ else if (p && unlikely(task_on_rq_queued(p) || current == p))
+ lsub_positive(&util_est, _task_util_est(p));
- /*
- * cur_ld_moved - load moved in current iteration
- * ld_moved - cumulative load moved across iterations
- */
- cur_ld_moved = detach_tasks(&env);
+ util = max(util, util_est);
+ }
- /*
- * We've detached some tasks from busiest_rq. Every
- * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
- * unlock busiest->lock, and we are able to be sure
- * that nobody can manipulate the tasks in parallel.
- * See task_rq_lock() family for the details.
- */
+ return min(util, arch_scale_cpu_capacity(cpu));
+}
- rq_unlock(busiest, &rf);
+unsigned long cpu_util_cfs(int cpu)
+{
+ return cpu_util(cpu, NULL, -1, 0);
+}
- if (cur_ld_moved) {
- attach_tasks(&env);
- ld_moved += cur_ld_moved;
- }
+unsigned long cpu_util_cfs_boost(int cpu)
+{
+ return cpu_util(cpu, NULL, -1, 1);
+}
- local_irq_restore(rf.flags);
+/*
+ * cpu_util_without: compute cpu utilization without any contributions from *p
+ * @cpu: the CPU which utilization is requested
+ * @p: the task which utilization should be discounted
+ *
+ * The utilization of a CPU is defined by the utilization of tasks currently
+ * enqueued on that CPU as well as tasks which are currently sleeping after an
+ * execution on that CPU.
+ *
+ * This method returns the utilization of the specified CPU by discounting the
+ * utilization of the specified task, whenever the task is currently
+ * contributing to the CPU utilization.
+ */
+unsigned long cpu_util_without(int cpu, struct task_struct *p)
+{
+ /* Task has no contribution or is new */
+ if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
+ p = NULL;
- if (env.flags & LBF_NEED_BREAK) {
- env.flags &= ~LBF_NEED_BREAK;
- /* Stop if we tried all running tasks */
- if (env.loop < busiest->nr_running)
- goto more_balance;
- }
+ return cpu_util(cpu, p, -1, 0);
+}
- /*
- * Revisit (affine) tasks on src_cpu that couldn't be moved to
- * us and move them to an alternate dst_cpu in our sched_group
- * where they can run. The upper limit on how many times we
- * iterate on same src_cpu is dependent on number of CPUs in our
- * sched_group.
- *
- * This changes load balance semantics a bit on who can move
- * load to a given_cpu. In addition to the given_cpu itself
- * (or a ilb_cpu acting on its behalf where given_cpu is
- * nohz-idle), we now have balance_cpu in a position to move
- * load to given_cpu. In rare situations, this may cause
- * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
- * _independently_ and at _same_ time to move some load to
- * given_cpu) causing excess load to be moved to given_cpu.
- * This however should not happen so much in practice and
- * moreover subsequent load balance cycles should correct the
- * excess load moved.
- */
- if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
+/*
+ * energy_env - Utilization landscape for energy estimation.
+ * @task_busy_time: Utilization contribution by the task for which we test the
+ * placement. Given by eenv_task_busy_time().
+ * @pd_busy_time: Utilization of the whole perf domain without the task
+ * contribution. Given by eenv_pd_busy_time().
+ * @cpu_cap: Maximum CPU capacity for the perf domain.
+ * @pd_cap: Entire perf domain capacity. (pd->nr_cpus * cpu_cap).
+ */
+struct energy_env {
+ unsigned long task_busy_time;
+ unsigned long pd_busy_time;
+ unsigned long cpu_cap;
+ unsigned long pd_cap;
+};
- /* Prevent to re-select dst_cpu via env's CPUs */
- __cpumask_clear_cpu(env.dst_cpu, env.cpus);
+/*
+ * Compute the task busy time for compute_energy(). This time cannot be
+ * injected directly into effective_cpu_util() because of the IRQ scaling.
+ * The latter only makes sense with the most recent CPUs where the task has
+ * run.
+ */
+static inline void eenv_task_busy_time(struct energy_env *eenv,
+ struct task_struct *p, int prev_cpu)
+{
+ unsigned long busy_time, max_cap = arch_scale_cpu_capacity(prev_cpu);
+ unsigned long irq = cpu_util_irq(cpu_rq(prev_cpu));
- env.dst_rq = cpu_rq(env.new_dst_cpu);
- env.dst_cpu = env.new_dst_cpu;
- env.flags &= ~LBF_DST_PINNED;
- env.loop = 0;
- env.loop_break = SCHED_NR_MIGRATE_BREAK;
+ if (unlikely(irq >= max_cap))
+ busy_time = max_cap;
+ else
+ busy_time = scale_irq_capacity(task_util_est(p), irq, max_cap);
- /*
- * Go back to "more_balance" rather than "redo" since we
- * need to continue with same src_cpu.
- */
- goto more_balance;
- }
+ eenv->task_busy_time = busy_time;
+}
- /*
- * We failed to reach balance because of affinity.
- */
- if (sd_parent) {
- int *group_imbalance = &sd_parent->groups->sgc->imbalance;
+/*
+ * Compute the perf_domain (PD) busy time for compute_energy(). Based on the
+ * utilization for each @pd_cpus, it however doesn't take into account
+ * clamping since the ratio (utilization / cpu_capacity) is already enough to
+ * scale the EM reported power consumption at the (eventually clamped)
+ * cpu_capacity.
+ *
+ * The contribution of the task @p for which we want to estimate the
+ * energy cost is removed (by cpu_util()) and must be calculated
+ * separately (see eenv_task_busy_time). This ensures:
+ *
+ * - A stable PD utilization, no matter which CPU of that PD we want to place
+ * the task on.
+ *
+ * - A fair comparison between CPUs as the task contribution (task_util())
+ * will always be the same no matter which CPU utilization we rely on
+ * (util_avg or util_est).
+ *
+ * Set @eenv busy time for the PD that spans @pd_cpus. This busy time can't
+ * exceed @eenv->pd_cap.
+ */
+static inline void eenv_pd_busy_time(struct energy_env *eenv,
+ struct cpumask *pd_cpus,
+ struct task_struct *p)
+{
+ unsigned long busy_time = 0;
+ int cpu;
- if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
- *group_imbalance = 1;
- }
+ for_each_cpu(cpu, pd_cpus) {
+ unsigned long util = cpu_util(cpu, p, -1, 0);
- /* All tasks on this runqueue were pinned by CPU affinity */
- if (unlikely(env.flags & LBF_ALL_PINNED)) {
- __cpumask_clear_cpu(cpu_of(busiest), cpus);
- /*
- * Attempting to continue load balancing at the current
- * sched_domain level only makes sense if there are
- * active CPUs remaining as possible busiest CPUs to
- * pull load from which are not contained within the
- * destination group that is receiving any migrated
- * load.
- */
- if (!cpumask_subset(cpus, env.dst_grpmask)) {
- env.loop = 0;
- env.loop_break = SCHED_NR_MIGRATE_BREAK;
- goto redo;
- }
- goto out_all_pinned;
- }
+ busy_time += effective_cpu_util(cpu, util, NULL, NULL);
}
- if (!ld_moved) {
- schedstat_inc(sd->lb_failed[idle]);
- /*
- * Increment the failure counter only on periodic balance.
- * We do not want newidle balance, which can be very
- * frequent, pollute the failure counter causing
- * excessive cache_hot migrations and active balances.
- *
- * Similarly for migration_misfit which is not related to
- * load/util migration, don't pollute nr_balance_failed.
- */
- if (idle != CPU_NEWLY_IDLE &&
- env.migration_type != migrate_misfit)
- sd->nr_balance_failed++;
+ eenv->pd_busy_time = min(eenv->pd_cap, busy_time);
+}
- if (need_active_balance(&env)) {
- unsigned long flags;
+/*
+ * Compute the maximum utilization for compute_energy() when the task @p
+ * is placed on the cpu @dst_cpu.
+ *
+ * Returns the maximum utilization among @eenv->cpus. This utilization can't
+ * exceed @eenv->cpu_cap.
+ */
+static inline unsigned long
+eenv_pd_max_util(struct energy_env *eenv, struct cpumask *pd_cpus,
+ struct task_struct *p, int dst_cpu)
+{
+ unsigned long max_util = 0;
+ int cpu;
- raw_spin_rq_lock_irqsave(busiest, flags);
+ for_each_cpu(cpu, pd_cpus) {
+ struct task_struct *tsk = (cpu == dst_cpu) ? p : NULL;
+ unsigned long util = cpu_util(cpu, p, dst_cpu, 1);
+ unsigned long eff_util, min, max;
- /*
- * Don't kick the active_load_balance_cpu_stop,
- * if the curr task on busiest CPU can't be
- * moved to this_cpu:
- */
- if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
- raw_spin_rq_unlock_irqrestore(busiest, flags);
- goto out_one_pinned;
- }
+ /*
+ * Performance domain frequency: utilization clamping
+ * must be considered since it affects the selection
+ * of the performance domain frequency.
+ * NOTE: in case RT tasks are running, by default the
+ * FREQUENCY_UTIL's utilization can be max OPP.
+ */
+ eff_util = effective_cpu_util(cpu, util, &min, &max);
- /* Record that we found at least one task that could run on this_cpu */
- env.flags &= ~LBF_ALL_PINNED;
+ /* Task's uclamp can modify min and max value */
+ if (tsk && uclamp_is_used()) {
+ min = max(min, uclamp_eff_value(p, UCLAMP_MIN));
/*
- * ->active_balance synchronizes accesses to
- * ->active_balance_work. Once set, it's cleared
- * only after active load balance is finished.
+ * If there is no active max uclamp constraint,
+ * directly use task's one, otherwise keep max.
*/
- if (!busiest->active_balance) {
- busiest->active_balance = 1;
- busiest->push_cpu = this_cpu;
- active_balance = 1;
- }
-
- preempt_disable();
- raw_spin_rq_unlock_irqrestore(busiest, flags);
- if (active_balance) {
- stop_one_cpu_nowait(cpu_of(busiest),
- active_load_balance_cpu_stop, busiest,
- &busiest->active_balance_work);
- }
- preempt_enable();
+ if (uclamp_rq_is_idle(cpu_rq(cpu)))
+ max = uclamp_eff_value(p, UCLAMP_MAX);
+ else
+ max = max(max, uclamp_eff_value(p, UCLAMP_MAX));
}
- } else {
- sd->nr_balance_failed = 0;
- }
-
- if (likely(!active_balance) || need_active_balance(&env)) {
- /* We were unbalanced, so reset the balancing interval */
- sd->balance_interval = sd->min_interval;
- }
- goto out;
-
-out_balanced:
- /*
- * We reach balance although we may have faced some affinity
- * constraints. Clear the imbalance flag only if other tasks got
- * a chance to move and fix the imbalance.
- */
- if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
- int *group_imbalance = &sd_parent->groups->sgc->imbalance;
-
- if (*group_imbalance)
- *group_imbalance = 0;
+ eff_util = sugov_effective_cpu_perf(cpu, eff_util, min, max);
+ max_util = max(max_util, eff_util);
}
-out_all_pinned:
- /*
- * We reach balance because all tasks are pinned at this level so
- * we can't migrate them. Let the imbalance flag set so parent level
- * can try to migrate them.
- */
- schedstat_inc(sd->lb_balanced[idle]);
-
- sd->nr_balance_failed = 0;
-
-out_one_pinned:
- ld_moved = 0;
-
- /*
- * sched_balance_newidle() disregards balance intervals, so we could
- * repeatedly reach this code, which would lead to balance_interval
- * skyrocketing in a short amount of time. Skip the balance_interval
- * increase logic to avoid that.
- *
- * Similarly misfit migration which is not necessarily an indication of
- * the system being busy and requires lb to backoff to let it settle
- * down.
- */
- if (env.idle == CPU_NEWLY_IDLE ||
- env.migration_type == migrate_misfit)
- goto out;
-
- /* tune up the balancing interval */
- if ((env.flags & LBF_ALL_PINNED &&
- sd->balance_interval < MAX_PINNED_INTERVAL) ||
- sd->balance_interval < sd->max_interval)
- sd->balance_interval *= 2;
-out:
- return ld_moved;
+ return min(max_util, eenv->cpu_cap);
}
+/*
+ * compute_energy(): Use the Energy Model to estimate the energy that @pd would
+ * consume for a given utilization landscape @eenv. When @dst_cpu < 0, the task
+ * contribution is ignored.
+ */
static inline unsigned long
-get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
+compute_energy(struct energy_env *eenv, struct perf_domain *pd,
+ struct cpumask *pd_cpus, struct task_struct *p, int dst_cpu)
{
- unsigned long interval = sd->balance_interval;
-
- if (cpu_busy)
- interval *= sd->busy_factor;
-
- /* scale ms to jiffies */
- interval = msecs_to_jiffies(interval);
-
- /*
- * Reduce likelihood of busy balancing at higher domains racing with
- * balancing at lower domains by preventing their balancing periods
- * from being multiples of each other.
- */
- if (cpu_busy)
- interval -= 1;
-
- interval = clamp(interval, 1UL, max_load_balance_interval);
+ unsigned long max_util = eenv_pd_max_util(eenv, pd_cpus, p, dst_cpu);
+ unsigned long busy_time = eenv->pd_busy_time;
+ unsigned long energy;
- return interval;
-}
+ if (dst_cpu >= 0)
+ busy_time = min(eenv->pd_cap, busy_time + eenv->task_busy_time);
-static inline void
-update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
-{
- unsigned long interval, next;
+ energy = em_cpu_energy(pd->em_pd, max_util, busy_time, eenv->cpu_cap);
- /* used by idle balance, so cpu_busy = 0 */
- interval = get_sd_balance_interval(sd, 0);
- next = sd->last_balance + interval;
+ trace_sched_compute_energy_tp(p, dst_cpu, energy, max_util, busy_time);
- if (time_after(*next_balance, next))
- *next_balance = next;
+ return energy;
}
/*
- * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
- * running tasks off the busiest CPU onto idle CPUs. It requires at
- * least 1 task to be running on each physical CPU where possible, and
- * avoids physical / logical imbalances.
+ * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
+ * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
+ * spare capacity in each performance domain and uses it as a potential
+ * candidate to execute the task. Then, it uses the Energy Model to figure
+ * out which of the CPU candidates is the most energy-efficient.
+ *
+ * The rationale for this heuristic is as follows. In a performance domain,
+ * all the most energy efficient CPU candidates (according to the Energy
+ * Model) are those for which we'll request a low frequency. When there are
+ * several CPUs for which the frequency request will be the same, we don't
+ * have enough data to break the tie between them, because the Energy Model
+ * only includes active power costs. With this model, if we assume that
+ * frequency requests follow utilization (e.g. using schedutil), the CPU with
+ * the maximum spare capacity in a performance domain is guaranteed to be among
+ * the best candidates of the performance domain.
+ *
+ * In practice, it could be preferable from an energy standpoint to pack
+ * small tasks on a CPU in order to let other CPUs go in deeper idle states,
+ * but that could also hurt our chances to go cluster idle, and we have no
+ * ways to tell with the current Energy Model if this is actually a good
+ * idea or not. So, find_energy_efficient_cpu() basically favors
+ * cluster-packing, and spreading inside a cluster. That should at least be
+ * a good thing for latency, and this is consistent with the idea that most
+ * of the energy savings of EAS come from the asymmetry of the system, and
+ * not so much from breaking the tie between identical CPUs. That's also the
+ * reason why EAS is enabled in the topology code only for systems where
+ * SD_ASYM_CPUCAPACITY is set.
+ *
+ * NOTE: Forkees are not accepted in the energy-aware wake-up path because
+ * they don't have any useful utilization data yet and it's not possible to
+ * forecast their impact on energy consumption. Consequently, they will be
+ * placed by sched_balance_find_dst_cpu() on the least loaded CPU, which might turn out
+ * to be energy-inefficient in some use-cases. The alternative would be to
+ * bias new tasks towards specific types of CPUs first, or to try to infer
+ * their util_avg from the parent task, but those heuristics could hurt
+ * other use-cases too. So, until someone finds a better way to solve this,
+ * let's keep things simple by re-using the existing slow path.
*/
-static int active_load_balance_cpu_stop(void *data)
+static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
{
- struct rq *busiest_rq = data;
- int busiest_cpu = cpu_of(busiest_rq);
- int target_cpu = busiest_rq->push_cpu;
- struct rq *target_rq = cpu_rq(target_cpu);
+ struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
+ unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
+ unsigned long p_util_min = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MIN) : 0;
+ unsigned long p_util_max = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MAX) : 1024;
+ struct root_domain *rd = this_rq()->rd;
+ int cpu, best_energy_cpu, target = -1;
+ int prev_fits = -1, best_fits = -1;
+ unsigned long best_thermal_cap = 0;
+ unsigned long prev_thermal_cap = 0;
struct sched_domain *sd;
- struct task_struct *p = NULL;
- struct rq_flags rf;
+ struct perf_domain *pd;
+ struct energy_env eenv;
+
+ rcu_read_lock();
+ pd = rcu_dereference(rd->pd);
+ if (!pd)
+ goto unlock;
- rq_lock_irq(busiest_rq, &rf);
/*
- * Between queueing the stop-work and running it is a hole in which
- * CPUs can become inactive. We should not move tasks from or to
- * inactive CPUs.
+ * Energy-aware wake-up happens on the lowest sched_domain starting
+ * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
*/
- if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
- goto out_unlock;
+ sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
+ while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
+ sd = sd->parent;
+ if (!sd)
+ goto unlock;
- /* Make sure the requested CPU hasn't gone down in the meantime: */
- if (unlikely(busiest_cpu != smp_processor_id() ||
- !busiest_rq->active_balance))
- goto out_unlock;
+ target = prev_cpu;
- /* Is there any task to move? */
- if (busiest_rq->nr_running <= 1)
- goto out_unlock;
+ sync_entity_load_avg(&p->se);
+ if (!task_util_est(p) && p_util_min == 0)
+ goto unlock;
- /*
- * This condition is "impossible", if it occurs
- * we need to fix it. Originally reported by
- * Bjorn Helgaas on a 128-CPU setup.
- */
- WARN_ON_ONCE(busiest_rq == target_rq);
+ eenv_task_busy_time(&eenv, p, prev_cpu);
- /* Search for an sd spanning us and the target CPU. */
- rcu_read_lock();
- for_each_domain(target_cpu, sd) {
- if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
- break;
- }
+ for (; pd; pd = pd->next) {
+ unsigned long util_min = p_util_min, util_max = p_util_max;
+ unsigned long cpu_cap, cpu_thermal_cap, util;
+ long prev_spare_cap = -1, max_spare_cap = -1;
+ unsigned long rq_util_min, rq_util_max;
+ unsigned long cur_delta, base_energy;
+ int max_spare_cap_cpu = -1;
+ int fits, max_fits = -1;
- if (likely(sd)) {
- struct lb_env env = {
- .sd = sd,
- .dst_cpu = target_cpu,
- .dst_rq = target_rq,
- .src_cpu = busiest_rq->cpu,
- .src_rq = busiest_rq,
- .idle = CPU_IDLE,
- .flags = LBF_ACTIVE_LB,
- };
-
- schedstat_inc(sd->alb_count);
- update_rq_clock(busiest_rq);
-
- p = detach_one_task(&env);
- if (p) {
- schedstat_inc(sd->alb_pushed);
- /* Active balancing done, reset the failure counter. */
- sd->nr_balance_failed = 0;
- } else {
- schedstat_inc(sd->alb_failed);
- }
- }
- rcu_read_unlock();
-out_unlock:
- busiest_rq->active_balance = 0;
- rq_unlock(busiest_rq, &rf);
+ cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
- if (p)
- attach_one_task(target_rq, p);
+ if (cpumask_empty(cpus))
+ continue;
- local_irq_enable();
+ /* Account thermal pressure for the energy estimation */
+ cpu = cpumask_first(cpus);
+ cpu_thermal_cap = arch_scale_cpu_capacity(cpu);
+ cpu_thermal_cap -= arch_scale_thermal_pressure(cpu);
- return 0;
-}
+ eenv.cpu_cap = cpu_thermal_cap;
+ eenv.pd_cap = 0;
-/*
- * This flag serializes load-balancing passes over large domains
- * (above the NODE topology level) - only one load-balancing instance
- * may run at a time, to reduce overhead on very large systems with
- * lots of CPUs and large NUMA distances.
- *
- * - Note that load-balancing passes triggered while another one
- * is executing are skipped and not re-tried.
- *
- * - Also note that this does not serialize rebalance_domains()
- * execution, as non-SD_SERIALIZE domains will still be
- * load-balanced in parallel.
- */
-static atomic_t sched_balance_running = ATOMIC_INIT(0);
+ for_each_cpu(cpu, cpus) {
+ struct rq *rq = cpu_rq(cpu);
-/*
- * Scale the max sched_balance_rq interval with the number of CPUs in the system.
- * This trades load-balance latency on larger machines for less cross talk.
- */
-void update_max_interval(void)
-{
- max_load_balance_interval = HZ*num_online_cpus()/10;
-}
+ eenv.pd_cap += cpu_thermal_cap;
-static inline bool update_newidle_cost(struct sched_domain *sd, u64 cost)
-{
- if (cost > sd->max_newidle_lb_cost) {
- /*
- * Track max cost of a domain to make sure to not delay the
- * next wakeup on the CPU.
- */
- sd->max_newidle_lb_cost = cost;
- sd->last_decay_max_lb_cost = jiffies;
- } else if (time_after(jiffies, sd->last_decay_max_lb_cost + HZ)) {
- /*
- * Decay the newidle max times by ~1% per second to ensure that
- * it is not outdated and the current max cost is actually
- * shorter.
- */
- sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 253) / 256;
- sd->last_decay_max_lb_cost = jiffies;
+ if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
+ continue;
- return true;
- }
+ if (!cpumask_test_cpu(cpu, p->cpus_ptr))
+ continue;
- return false;
-}
+ util = cpu_util(cpu, p, cpu, 0);
+ cpu_cap = capacity_of(cpu);
-/*
- * It checks each scheduling domain to see if it is due to be balanced,
- * and initiates a balancing operation if so.
- *
- * Balancing parameters are set up in init_sched_domains.
- */
-static void sched_balance_domains(struct rq *rq, enum cpu_idle_type idle)
-{
- int continue_balancing = 1;
- int cpu = rq->cpu;
- int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
- unsigned long interval;
- struct sched_domain *sd;
- /* Earliest time when we have to do rebalance again */
- unsigned long next_balance = jiffies + 60*HZ;
- int update_next_balance = 0;
- int need_serialize, need_decay = 0;
- u64 max_cost = 0;
+ /*
+ * Skip CPUs that cannot satisfy the capacity request.
+ * IOW, placing the task there would make the CPU
+ * overutilized. Take uclamp into account to see how
+ * much capacity we can get out of the CPU; this is
+ * aligned with sched_cpu_util().
+ */
+ if (uclamp_is_used() && !uclamp_rq_is_idle(rq)) {
+ /*
+ * Open code uclamp_rq_util_with() except for
+ * the clamp() part. I.e.: apply max aggregation
+ * only. util_fits_cpu() logic requires to
+ * operate on non clamped util but must use the
+ * max-aggregated uclamp_{min, max}.
+ */
+ rq_util_min = uclamp_rq_get(rq, UCLAMP_MIN);
+ rq_util_max = uclamp_rq_get(rq, UCLAMP_MAX);
- rcu_read_lock();
- for_each_domain(cpu, sd) {
- /*
- * Decay the newidle max times here because this is a regular
- * visit to all the domains.
- */
- need_decay = update_newidle_cost(sd, 0);
- max_cost += sd->max_newidle_lb_cost;
+ util_min = max(rq_util_min, p_util_min);
+ util_max = max(rq_util_max, p_util_max);
+ }
- /*
- * Stop the load balance at this level. There is another
- * CPU in our sched group which is doing load balancing more
- * actively.
- */
- if (!continue_balancing) {
- if (need_decay)
+ fits = util_fits_cpu(util, util_min, util_max, cpu);
+ if (!fits)
continue;
- break;
- }
- interval = get_sd_balance_interval(sd, busy);
-
- need_serialize = sd->flags & SD_SERIALIZE;
- if (need_serialize) {
- if (atomic_cmpxchg_acquire(&sched_balance_running, 0, 1))
- goto out;
- }
+ lsub_positive(&cpu_cap, util);
- if (time_after_eq(jiffies, sd->last_balance + interval)) {
- if (sched_balance_rq(cpu, rq, sd, idle, &continue_balancing)) {
+ if (cpu == prev_cpu) {
+ /* Always use prev_cpu as a candidate. */
+ prev_spare_cap = cpu_cap;
+ prev_fits = fits;
+ } else if ((fits > max_fits) ||
+ ((fits == max_fits) && ((long)cpu_cap > max_spare_cap))) {
/*
- * The LBF_DST_PINNED logic could have changed
- * env->dst_cpu, so we can't know our idle
- * state even if we migrated tasks. Update it.
+ * Find the CPU with the maximum spare capacity
+ * among the remaining CPUs in the performance
+ * domain.
*/
- idle = idle_cpu(cpu);
- busy = !idle && !sched_idle_cpu(cpu);
+ max_spare_cap = cpu_cap;
+ max_spare_cap_cpu = cpu;
+ max_fits = fits;
}
- sd->last_balance = jiffies;
- interval = get_sd_balance_interval(sd, busy);
}
- if (need_serialize)
- atomic_set_release(&sched_balance_running, 0);
-out:
- if (time_after(next_balance, sd->last_balance + interval)) {
- next_balance = sd->last_balance + interval;
- update_next_balance = 1;
- }
- }
- if (need_decay) {
- /*
- * Ensure the rq-wide value also decays but keep it at a
- * reasonable floor to avoid funnies with rq->avg_idle.
- */
- rq->max_idle_balance_cost =
- max((u64)sysctl_sched_migration_cost, max_cost);
- }
- rcu_read_unlock();
- /*
- * next_balance will be updated only when there is a need.
- * When the cpu is attached to null domain for ex, it will not be
- * updated.
- */
- if (likely(update_next_balance))
- rq->next_balance = next_balance;
+ if (max_spare_cap_cpu < 0 && prev_spare_cap < 0)
+ continue;
-}
+ eenv_pd_busy_time(&eenv, cpus, p);
+ /* Compute the 'base' energy of the pd, without @p */
+ base_energy = compute_energy(&eenv, pd, cpus, p, -1);
-static inline int on_null_domain(struct rq *rq)
-{
- return unlikely(!rcu_dereference_sched(rq->sd));
-}
+ /* Evaluate the energy impact of using prev_cpu. */
+ if (prev_spare_cap > -1) {
+ prev_delta = compute_energy(&eenv, pd, cpus, p,
+ prev_cpu);
+ /* CPU utilization has changed */
+ if (prev_delta < base_energy)
+ goto unlock;
+ prev_delta -= base_energy;
+ prev_thermal_cap = cpu_thermal_cap;
+ best_delta = min(best_delta, prev_delta);
+ }
-#ifdef CONFIG_NO_HZ_COMMON
-/*
- * NOHZ idle load balancing (ILB) details:
- *
- * - When one of the busy CPUs notices that there may be an idle rebalancing
- * needed, they will kick the idle load balancer, which then does idle
- * load balancing for all the idle CPUs.
- *
- * - HK_TYPE_MISC CPUs are used for this task, because HK_TYPE_SCHED is not set
- * anywhere yet.
- */
-static inline int find_new_ilb(void)
-{
- const struct cpumask *hk_mask;
- int ilb_cpu;
+ /* Evaluate the energy impact of using max_spare_cap_cpu. */
+ if (max_spare_cap_cpu >= 0 && max_spare_cap > prev_spare_cap) {
+ /* Current best energy cpu fits better */
+ if (max_fits < best_fits)
+ continue;
- hk_mask = housekeeping_cpumask(HK_TYPE_MISC);
+ /*
+ * Both don't fit performance hint (i.e. uclamp_min)
+ * but best energy cpu has better capacity.
+ */
+ if ((max_fits < 0) &&
+ (cpu_thermal_cap <= best_thermal_cap))
+ continue;
- for_each_cpu_and(ilb_cpu, nohz.idle_cpus_mask, hk_mask) {
+ cur_delta = compute_energy(&eenv, pd, cpus, p,
+ max_spare_cap_cpu);
+ /* CPU utilization has changed */
+ if (cur_delta < base_energy)
+ goto unlock;
+ cur_delta -= base_energy;
- if (ilb_cpu == smp_processor_id())
- continue;
+ /*
+ * Both fit for the task but best energy cpu has lower
+ * energy impact.
+ */
+ if ((max_fits > 0) && (best_fits > 0) &&
+ (cur_delta >= best_delta))
+ continue;
- if (idle_cpu(ilb_cpu))
- return ilb_cpu;
+ best_delta = cur_delta;
+ best_energy_cpu = max_spare_cap_cpu;
+ best_fits = max_fits;
+ best_thermal_cap = cpu_thermal_cap;
+ }
}
+ rcu_read_unlock();
- return -1;
-}
-
-/*
- * Kick a CPU to do the NOHZ balancing, if it is time for it, via a cross-CPU
- * SMP function call (IPI).
- *
- * We pick the first idle CPU in the HK_TYPE_MISC housekeeping set (if there is one).
- */
-static void kick_ilb(unsigned int flags)
-{
- int ilb_cpu;
-
- /*
- * Increase nohz.next_balance only when if full ilb is triggered but
- * not if we only update stats.
- */
- if (flags & NOHZ_BALANCE_KICK)
- nohz.next_balance = jiffies+1;
+ if ((best_fits > prev_fits) ||
+ ((best_fits > 0) && (best_delta < prev_delta)) ||
+ ((best_fits < 0) && (best_thermal_cap > prev_thermal_cap)))
+ target = best_energy_cpu;
- ilb_cpu = find_new_ilb();
- if (ilb_cpu < 0)
- return;
+ return target;
- /*
- * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
- * the first flag owns it; cleared by nohz_csd_func().
- */
- flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
- if (flags & NOHZ_KICK_MASK)
- return;
+unlock:
+ rcu_read_unlock();
- /*
- * This way we generate an IPI on the target CPU which
- * is idle, and the softirq performing NOHZ idle load balancing
- * will be run before returning from the IPI.
- */
- smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd);
+ return target;
}
/*
- * Current decision point for kicking the idle load balancer in the presence
- * of idle CPUs in the system.
+ * select_task_rq_fair: Select target runqueue for the waking task in domains
+ * that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE,
+ * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
+ *
+ * Balances load by selecting the idlest CPU in the idlest group, or under
+ * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
+ *
+ * Returns the target CPU number.
*/
-static void nohz_balancer_kick(struct rq *rq)
+static int
+select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
{
- unsigned long now = jiffies;
- struct sched_domain_shared *sds;
- struct sched_domain *sd;
- int nr_busy, i, cpu = rq->cpu;
- unsigned int flags = 0;
-
- if (unlikely(rq->idle_balance))
- return;
-
- /*
- * We may be recently in ticked or tickless idle mode. At the first
- * busy tick after returning from idle, we will update the busy stats.
- */
- nohz_balance_exit_idle(rq);
+ int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
+ struct sched_domain *tmp, *sd = NULL;
+ int cpu = smp_processor_id();
+ int new_cpu = prev_cpu;
+ int want_affine = 0;
+ /* SD_flags and WF_flags share the first nibble */
+ int sd_flag = wake_flags & 0xF;
/*
- * None are in tickless mode and hence no need for NOHZ idle load
- * balancing:
+ * required for stable ->cpus_allowed
*/
- if (likely(!atomic_read(&nohz.nr_cpus)))
- return;
+ lockdep_assert_held(&p->pi_lock);
+ if (wake_flags & WF_TTWU) {
+ record_wakee(p);
- if (READ_ONCE(nohz.has_blocked) &&
- time_after(now, READ_ONCE(nohz.next_blocked)))
- flags = NOHZ_STATS_KICK;
+ if ((wake_flags & WF_CURRENT_CPU) &&
+ cpumask_test_cpu(cpu, p->cpus_ptr))
+ return cpu;
- if (time_before(now, nohz.next_balance))
- goto out;
+ if (!is_rd_overutilized(this_rq()->rd)) {
+ new_cpu = find_energy_efficient_cpu(p, prev_cpu);
+ if (new_cpu >= 0)
+ return new_cpu;
+ new_cpu = prev_cpu;
+ }
- if (rq->nr_running >= 2) {
- flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
- goto out;
+ want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
}
rcu_read_lock();
-
- sd = rcu_dereference(rq->sd);
- if (sd) {
- /*
- * If there's a runnable CFS task and the current CPU has reduced
- * capacity, kick the ILB to see if there's a better CPU to run on:
- */
- if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
- flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
- goto unlock;
- }
- }
-
- sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
- if (sd) {
+ for_each_domain(cpu, tmp) {
/*
- * When ASYM_PACKING; see if there's a more preferred CPU
- * currently idle; in which case, kick the ILB to move tasks
- * around.
- *
- * When balancing between cores, all the SMT siblings of the
- * preferred CPU must be idle.
+ * If both 'cpu' and 'prev_cpu' are part of this domain,
+ * cpu is a valid SD_WAKE_AFFINE target.
*/
- for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
- if (sched_asym(sd, i, cpu)) {
- flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
- goto unlock;
- }
- }
- }
+ if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
+ cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
+ if (cpu != prev_cpu)
+ new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
- sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
- if (sd) {
- /*
- * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
- * to run the misfit task on.
- */
- if (check_misfit_status(rq)) {
- flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
- goto unlock;
+ sd = NULL; /* Prefer wake_affine over balance flags */
+ break;
}
/*
- * For asymmetric systems, we do not want to nicely balance
- * cache use, instead we want to embrace asymmetry and only
- * ensure tasks have enough CPU capacity.
- *
- * Skip the LLC logic because it's not relevant in that case.
+ * Usually only true for WF_EXEC and WF_FORK, as sched_domains
+ * usually do not have SD_BALANCE_WAKE set. That means wakeup
+ * will usually go to the fast path.
*/
- goto unlock;
+ if (tmp->flags & sd_flag)
+ sd = tmp;
+ else if (!want_affine)
+ break;
}
- sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
- if (sds) {
- /*
- * If there is an imbalance between LLC domains (IOW we could
- * increase the overall cache utilization), we need a less-loaded LLC
- * domain to pull some load from. Likewise, we may need to spread
- * load within the current LLC domain (e.g. packed SMT cores but
- * other CPUs are idle). We can't really know from here how busy
- * the others are - so just get a NOHZ balance going if it looks
- * like this LLC domain has tasks we could move.
- */
- nr_busy = atomic_read(&sds->nr_busy_cpus);
- if (nr_busy > 1) {
- flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
- goto unlock;
- }
+ if (unlikely(sd)) {
+ /* Slow path */
+ new_cpu = sched_balance_find_dst_cpu(sd, p, cpu, prev_cpu, sd_flag);
+ } else if (wake_flags & WF_TTWU) { /* XXX always ? */
+ /* Fast path */
+ new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
}
-unlock:
rcu_read_unlock();
-out:
- if (READ_ONCE(nohz.needs_update))
- flags |= NOHZ_NEXT_KICK;
- if (flags)
- kick_ilb(flags);
+ return new_cpu;
}
-static void set_cpu_sd_state_busy(int cpu)
+/*
+ * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
+ * cfs_rq_of(p) references at time of call are still valid and identify the
+ * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
+ */
+static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
{
- struct sched_domain *sd;
-
- rcu_read_lock();
- sd = rcu_dereference(per_cpu(sd_llc, cpu));
-
- if (!sd || !sd->nohz_idle)
- goto unlock;
- sd->nohz_idle = 0;
-
- atomic_inc(&sd->shared->nr_busy_cpus);
-unlock:
- rcu_read_unlock();
-}
+ struct sched_entity *se = &p->se;
-void nohz_balance_exit_idle(struct rq *rq)
-{
- SCHED_WARN_ON(rq != this_rq());
+ if (!task_on_rq_migrating(p)) {
+ remove_entity_load_avg(se);
- if (likely(!rq->nohz_tick_stopped))
- return;
+ /*
+ * Here, the task's PELT values have been updated according to
+ * the current rq's clock. But if that clock hasn't been
+ * updated in a while, a substantial idle time will be missed,
+ * leading to an inflation after wake-up on the new rq.
+ *
+ * Estimate the missing time from the cfs_rq last_update_time
+ * and update sched_avg to improve the PELT continuity after
+ * migration.
+ */
+ migrate_se_pelt_lag(se);
+ }
- rq->nohz_tick_stopped = 0;
- cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
- atomic_dec(&nohz.nr_cpus);
+ /* Tell new CPU we are migrated */
+ se->avg.last_update_time = 0;
- set_cpu_sd_state_busy(rq->cpu);
+ update_scan_period(p, new_cpu);
}
-static void set_cpu_sd_state_idle(int cpu)
+static void task_dead_fair(struct task_struct *p)
{
- struct sched_domain *sd;
-
- rcu_read_lock();
- sd = rcu_dereference(per_cpu(sd_llc, cpu));
-
- if (!sd || sd->nohz_idle)
- goto unlock;
- sd->nohz_idle = 1;
-
- atomic_dec(&sd->shared->nr_busy_cpus);
-unlock:
- rcu_read_unlock();
+ remove_entity_load_avg(&p->se);
}
/*
- * This routine will record that the CPU is going idle with tick stopped.
- * This info will be used in performing idle load balancing in the future.
+ * Set the max capacity the task is allowed to run at for misfit detection.
*/
-void nohz_balance_enter_idle(int cpu)
+static void set_task_max_allowed_capacity(struct task_struct *p)
{
- struct rq *rq = cpu_rq(cpu);
-
- SCHED_WARN_ON(cpu != smp_processor_id());
-
- /* If this CPU is going down, then nothing needs to be done: */
- if (!cpu_active(cpu))
- return;
-
- /* Spare idle load balancing on CPUs that don't want to be disturbed: */
- if (!housekeeping_cpu(cpu, HK_TYPE_SCHED))
- return;
-
- /*
- * Can be set safely without rq->lock held
- * If a clear happens, it will have evaluated last additions because
- * rq->lock is held during the check and the clear
- */
- rq->has_blocked_load = 1;
-
- /*
- * The tick is still stopped but load could have been added in the
- * meantime. We set the nohz.has_blocked flag to trig a check of the
- * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
- * of nohz.has_blocked can only happen after checking the new load
- */
- if (rq->nohz_tick_stopped)
- goto out;
+ struct asym_cap_data *entry;
- /* If we're a completely isolated CPU, we don't play: */
- if (on_null_domain(rq))
+ if (!sched_asym_cpucap_active())
return;
- rq->nohz_tick_stopped = 1;
-
- cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
- atomic_inc(&nohz.nr_cpus);
-
- /*
- * Ensures that if nohz_idle_balance() fails to observe our
- * @idle_cpus_mask store, it must observe the @has_blocked
- * and @needs_update stores.
- */
- smp_mb__after_atomic();
+ rcu_read_lock();
+ list_for_each_entry_rcu(entry, &asym_cap_list, link) {
+ cpumask_t *cpumask;
- set_cpu_sd_state_idle(cpu);
+ cpumask = cpu_capacity_span(entry);
+ if (!cpumask_intersects(p->cpus_ptr, cpumask))
+ continue;
- WRITE_ONCE(nohz.needs_update, 1);
-out:
- /*
- * Each time a cpu enter idle, we assume that it has blocked load and
- * enable the periodic update of the load of idle CPUs
- */
- WRITE_ONCE(nohz.has_blocked, 1);
+ p->max_allowed_capacity = entry->capacity;
+ break;
+ }
+ rcu_read_unlock();
}
-static bool update_nohz_stats(struct rq *rq)
+static void set_cpus_allowed_fair(struct task_struct *p, struct affinity_context *ctx)
{
- unsigned int cpu = rq->cpu;
-
- if (!rq->has_blocked_load)
- return false;
-
- if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
- return false;
+ set_cpus_allowed_common(p, ctx);
+ set_task_max_allowed_capacity(p);
+}
- if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick)))
- return true;
+static int
+balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+ if (rq->nr_running)
+ return 1;
- sched_balance_update_blocked_averages(cpu);
+ return sched_balance_newidle(rq, rf) != 0;
+}
+#else
+static inline void set_task_max_allowed_capacity(struct task_struct *p) {}
+#endif /* CONFIG_SMP */
- return rq->has_blocked_load;
+static void set_next_buddy(struct sched_entity *se)
+{
+ for_each_sched_entity(se) {
+ if (SCHED_WARN_ON(!se->on_rq))
+ return;
+ if (se_is_idle(se))
+ return;
+ cfs_rq_of(se)->next = se;
+ }
}
/*
- * Internal function that runs load balance for all idle CPUs. The load balance
- * can be a simple update of blocked load or a complete load balance with
- * tasks movement depending of flags.
+ * Preempt the current task with a newly woken task if needed:
*/
-static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags)
-{
- /* Earliest time when we have to do rebalance again */
- unsigned long now = jiffies;
- unsigned long next_balance = now + 60*HZ;
- bool has_blocked_load = false;
- int update_next_balance = 0;
- int this_cpu = this_rq->cpu;
- int balance_cpu;
- struct rq *rq;
+static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int wake_flags)
+{
+ struct task_struct *curr = rq->curr;
+ struct sched_entity *se = &curr->se, *pse = &p->se;
+ struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+ int cse_is_idle, pse_is_idle;
- SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
+ if (unlikely(se == pse))
+ return;
/*
- * We assume there will be no idle load after this update and clear
- * the has_blocked flag. If a cpu enters idle in the mean time, it will
- * set the has_blocked flag and trigger another update of idle load.
- * Because a cpu that becomes idle, is added to idle_cpus_mask before
- * setting the flag, we are sure to not clear the state and not
- * check the load of an idle cpu.
- *
- * Same applies to idle_cpus_mask vs needs_update.
+ * This is possible from callers such as attach_tasks(), in which we
+ * unconditionally wakeup_preempt() after an enqueue (which may have
+ * lead to a throttle). This both saves work and prevents false
+ * next-buddy nomination below.
*/
- if (flags & NOHZ_STATS_KICK)
- WRITE_ONCE(nohz.has_blocked, 0);
- if (flags & NOHZ_NEXT_KICK)
- WRITE_ONCE(nohz.needs_update, 0);
+ if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
+ return;
- /*
- * Ensures that if we miss the CPU, we must see the has_blocked
- * store from nohz_balance_enter_idle().
- */
- smp_mb();
+ if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) {
+ set_next_buddy(pse);
+ }
/*
- * Start with the next CPU after this_cpu so we will end with this_cpu and let a
- * chance for other idle cpu to pull load.
+ * We can come here with TIF_NEED_RESCHED already set from new task
+ * wake up path.
+ *
+ * Note: this also catches the edge-case of curr being in a throttled
+ * group (e.g. via set_curr_task), since update_curr() (in the
+ * enqueue of curr) will have resulted in resched being set. This
+ * prevents us from potentially nominating it as a false LAST_BUDDY
+ * below.
*/
- for_each_cpu_wrap(balance_cpu, nohz.idle_cpus_mask, this_cpu+1) {
- if (!idle_cpu(balance_cpu))
- continue;
-
- /*
- * If this CPU gets work to do, stop the load balancing
- * work being done for other CPUs. Next load
- * balancing owner will pick it up.
- */
- if (need_resched()) {
- if (flags & NOHZ_STATS_KICK)
- has_blocked_load = true;
- if (flags & NOHZ_NEXT_KICK)
- WRITE_ONCE(nohz.needs_update, 1);
- goto abort;
- }
+ if (test_tsk_need_resched(curr))
+ return;
- rq = cpu_rq(balance_cpu);
+ /* Idle tasks are by definition preempted by non-idle tasks. */
+ if (unlikely(task_has_idle_policy(curr)) &&
+ likely(!task_has_idle_policy(p)))
+ goto preempt;
- if (flags & NOHZ_STATS_KICK)
- has_blocked_load |= update_nohz_stats(rq);
+ /*
+ * Batch and idle tasks do not preempt non-idle tasks (their preemption
+ * is driven by the tick):
+ */
+ if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
+ return;
- /*
- * If time for next balance is due,
- * do the balance.
- */
- if (time_after_eq(jiffies, rq->next_balance)) {
- struct rq_flags rf;
+ find_matching_se(&se, &pse);
+ WARN_ON_ONCE(!pse);
- rq_lock_irqsave(rq, &rf);
- update_rq_clock(rq);
- rq_unlock_irqrestore(rq, &rf);
+ cse_is_idle = se_is_idle(se);
+ pse_is_idle = se_is_idle(pse);
- if (flags & NOHZ_BALANCE_KICK)
- sched_balance_domains(rq, CPU_IDLE);
- }
+ /*
+ * Preempt an idle group in favor of a non-idle group (and don't preempt
+ * in the inverse case).
+ */
+ if (cse_is_idle && !pse_is_idle)
+ goto preempt;
+ if (cse_is_idle != pse_is_idle)
+ return;
- if (time_after(next_balance, rq->next_balance)) {
- next_balance = rq->next_balance;
- update_next_balance = 1;
- }
- }
+ cfs_rq = cfs_rq_of(se);
+ update_curr(cfs_rq);
/*
- * next_balance will be updated only when there is a need.
- * When the CPU is attached to null domain for ex, it will not be
- * updated.
+ * XXX pick_eevdf(cfs_rq) != se ?
*/
- if (likely(update_next_balance))
- nohz.next_balance = next_balance;
+ if (pick_eevdf(cfs_rq) == pse)
+ goto preempt;
- if (flags & NOHZ_STATS_KICK)
- WRITE_ONCE(nohz.next_blocked,
- now + msecs_to_jiffies(LOAD_AVG_PERIOD));
+ return;
-abort:
- /* There is still blocked load, enable periodic update */
- if (has_blocked_load)
- WRITE_ONCE(nohz.has_blocked, 1);
+preempt:
+ resched_curr(rq);
}
-/*
- * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
- * rebalancing for all the CPUs for whom scheduler ticks are stopped.
- */
-static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
+#ifdef CONFIG_SMP
+static struct task_struct *pick_task_fair(struct rq *rq)
{
- unsigned int flags = this_rq->nohz_idle_balance;
-
- if (!flags)
- return false;
-
- this_rq->nohz_idle_balance = 0;
+ struct sched_entity *se;
+ struct cfs_rq *cfs_rq;
- if (idle != CPU_IDLE)
- return false;
+again:
+ cfs_rq = &rq->cfs;
+ if (!cfs_rq->nr_running)
+ return NULL;
- _nohz_idle_balance(this_rq, flags);
+ do {
+ struct sched_entity *curr = cfs_rq->curr;
- return true;
-}
+ /* When we pick for a remote RQ, we'll not have done put_prev_entity() */
+ if (curr) {
+ if (curr->on_rq)
+ update_curr(cfs_rq);
+ else
+ curr = NULL;
-/*
- * Check if we need to directly run the ILB for updating blocked load before
- * entering idle state. Here we run ILB directly without issuing IPIs.
- *
- * Note that when this function is called, the tick may not yet be stopped on
- * this CPU yet. nohz.idle_cpus_mask is updated only when tick is stopped and
- * cleared on the next busy tick. In other words, nohz.idle_cpus_mask updates
- * don't align with CPUs enter/exit idle to avoid bottlenecks due to high idle
- * entry/exit rate (usec). So it is possible that _nohz_idle_balance() is
- * called from this function on (this) CPU that's not yet in the mask. That's
- * OK because the goal of nohz_run_idle_balance() is to run ILB only for
- * updating the blocked load of already idle CPUs without waking up one of
- * those idle CPUs and outside the preempt disable / IRQ off phase of the local
- * cpu about to enter idle, because it can take a long time.
- */
-void nohz_run_idle_balance(int cpu)
-{
- unsigned int flags;
+ if (unlikely(check_cfs_rq_runtime(cfs_rq)))
+ goto again;
+ }
- flags = atomic_fetch_andnot(NOHZ_NEWILB_KICK, nohz_flags(cpu));
+ se = pick_next_entity(cfs_rq);
+ cfs_rq = group_cfs_rq(se);
+ } while (cfs_rq);
- /*
- * Update the blocked load only if no SCHED_SOFTIRQ is about to happen
- * (i.e. NOHZ_STATS_KICK set) and will do the same.
- */
- if ((flags == NOHZ_NEWILB_KICK) && !need_resched())
- _nohz_idle_balance(cpu_rq(cpu), NOHZ_STATS_KICK);
+ return task_of(se);
}
+#endif
-static void nohz_newidle_balance(struct rq *this_rq)
+struct task_struct *
+pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
- int this_cpu = this_rq->cpu;
-
- /*
- * This CPU doesn't want to be disturbed by scheduler
- * housekeeping
- */
- if (!housekeeping_cpu(this_cpu, HK_TYPE_SCHED))
- return;
+ struct cfs_rq *cfs_rq = &rq->cfs;
+ struct sched_entity *se;
+ struct task_struct *p;
+ int new_tasks;
- /* Will wake up very soon. No time for doing anything else*/
- if (this_rq->avg_idle < sysctl_sched_migration_cost)
- return;
+again:
+ if (!sched_fair_runnable(rq))
+ goto idle;
- /* Don't need to update blocked load of idle CPUs*/
- if (!READ_ONCE(nohz.has_blocked) ||
- time_before(jiffies, READ_ONCE(nohz.next_blocked)))
- return;
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ if (!prev || prev->sched_class != &fair_sched_class)
+ goto simple;
/*
- * Set the need to trigger ILB in order to update blocked load
- * before entering idle state.
+ * Because of the set_next_buddy() in dequeue_task_fair() it is rather
+ * likely that a next task is from the same cgroup as the current.
+ *
+ * Therefore attempt to avoid putting and setting the entire cgroup
+ * hierarchy, only change the part that actually changes.
*/
- atomic_or(NOHZ_NEWILB_KICK, nohz_flags(this_cpu));
-}
-#else /* !CONFIG_NO_HZ_COMMON */
-static inline void nohz_balancer_kick(struct rq *rq) { }
-
-static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
-{
- return false;
-}
+ do {
+ struct sched_entity *curr = cfs_rq->curr;
-static inline void nohz_newidle_balance(struct rq *this_rq) { }
-#endif /* CONFIG_NO_HZ_COMMON */
+ /*
+ * Since we got here without doing put_prev_entity() we also
+ * have to consider cfs_rq->curr. If it is still a runnable
+ * entity, update_curr() will update its vruntime, otherwise
+ * forget we've ever seen it.
+ */
+ if (curr) {
+ if (curr->on_rq)
+ update_curr(cfs_rq);
+ else
+ curr = NULL;
-/*
- * sched_balance_newidle is called by schedule() if this_cpu is about to become
- * idle. Attempts to pull tasks from other CPUs.
- *
- * Returns:
- * < 0 - we released the lock and there are !fair tasks present
- * 0 - failed, no new tasks
- * > 0 - success, new (fair) tasks present
- */
-static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
-{
- unsigned long next_balance = jiffies + HZ;
- int this_cpu = this_rq->cpu;
- int continue_balancing = 1;
- u64 t0, t1, curr_cost = 0;
- struct sched_domain *sd;
- int pulled_task = 0;
+ /*
+ * This call to check_cfs_rq_runtime() will do the
+ * throttle and dequeue its entity in the parent(s).
+ * Therefore the nr_running test will indeed
+ * be correct.
+ */
+ if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
+ cfs_rq = &rq->cfs;
- update_misfit_status(NULL, this_rq);
+ if (!cfs_rq->nr_running)
+ goto idle;
- /*
- * There is a task waiting to run. No need to search for one.
- * Return 0; the task will be enqueued when switching to idle.
- */
- if (this_rq->ttwu_pending)
- return 0;
+ goto simple;
+ }
+ }
- /*
- * We must set idle_stamp _before_ calling sched_balance_rq()
- * for CPU_NEWLY_IDLE, such that we measure the this duration
- * as idle time.
- */
- this_rq->idle_stamp = rq_clock(this_rq);
+ se = pick_next_entity(cfs_rq);
+ cfs_rq = group_cfs_rq(se);
+ } while (cfs_rq);
- /*
- * Do not pull tasks towards !active CPUs...
- */
- if (!cpu_active(this_cpu))
- return 0;
+ p = task_of(se);
/*
- * This is OK, because current is on_cpu, which avoids it being picked
- * for load-balance and preemption/IRQs are still disabled avoiding
- * further scheduler activity on it and we're being very careful to
- * re-start the picking loop.
+ * Since we haven't yet done put_prev_entity and if the selected task
+ * is a different task than we started out with, try and touch the
+ * least amount of cfs_rqs.
*/
- rq_unpin_lock(this_rq, rf);
-
- rcu_read_lock();
- sd = rcu_dereference_check_sched_domain(this_rq->sd);
+ if (prev != p) {
+ struct sched_entity *pse = &prev->se;
- if (!get_rd_overloaded(this_rq->rd) ||
- (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {
+ while (!(cfs_rq = is_same_group(se, pse))) {
+ int se_depth = se->depth;
+ int pse_depth = pse->depth;
- if (sd)
- update_next_balance(sd, &next_balance);
- rcu_read_unlock();
+ if (se_depth <= pse_depth) {
+ put_prev_entity(cfs_rq_of(pse), pse);
+ pse = parent_entity(pse);
+ }
+ if (se_depth >= pse_depth) {
+ set_next_entity(cfs_rq_of(se), se);
+ se = parent_entity(se);
+ }
+ }
- goto out;
+ put_prev_entity(cfs_rq, pse);
+ set_next_entity(cfs_rq, se);
}
- rcu_read_unlock();
-
- raw_spin_rq_unlock(this_rq);
- t0 = sched_clock_cpu(this_cpu);
- sched_balance_update_blocked_averages(this_cpu);
-
- rcu_read_lock();
- for_each_domain(this_cpu, sd) {
- u64 domain_cost;
-
- update_next_balance(sd, &next_balance);
+ goto done;
+simple:
+#endif
+ if (prev)
+ put_prev_task(rq, prev);
- if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
- break;
+ do {
+ se = pick_next_entity(cfs_rq);
+ set_next_entity(cfs_rq, se);
+ cfs_rq = group_cfs_rq(se);
+ } while (cfs_rq);
- if (sd->flags & SD_BALANCE_NEWIDLE) {
+ p = task_of(se);
- pulled_task = sched_balance_rq(this_cpu, this_rq,
- sd, CPU_NEWLY_IDLE,
- &continue_balancing);
+done: __maybe_unused;
+#ifdef CONFIG_SMP
+ /*
+ * Move the next running task to the front of
+ * the list, so our cfs_tasks list becomes MRU
+ * one.
+ */
+ list_move(&p->se.group_node, &rq->cfs_tasks);
+#endif
- t1 = sched_clock_cpu(this_cpu);
- domain_cost = t1 - t0;
- update_newidle_cost(sd, domain_cost);
+ if (hrtick_enabled_fair(rq))
+ hrtick_start_fair(rq, p);
- curr_cost += domain_cost;
- t0 = t1;
- }
+ update_misfit_status(p, rq);
+ sched_fair_update_stop_tick(rq, p);
- /*
- * Stop searching for tasks to pull if there are
- * now runnable tasks on this rq.
- */
- if (pulled_task || !continue_balancing)
- break;
- }
- rcu_read_unlock();
+ return p;
- raw_spin_rq_lock(this_rq);
+idle:
+ if (!rf)
+ return NULL;
- if (curr_cost > this_rq->max_idle_balance_cost)
- this_rq->max_idle_balance_cost = curr_cost;
+ new_tasks = sched_balance_newidle(rq, rf);
/*
- * While browsing the domains, we released the rq lock, a task could
- * have been enqueued in the meantime. Since we're not going idle,
- * pretend we pulled a task.
+ * Because sched_balance_newidle() releases (and re-acquires) rq->lock, it is
+ * possible for any higher priority task to appear. In that case we
+ * must re-start the pick_next_entity() loop.
*/
- if (this_rq->cfs.h_nr_running && !pulled_task)
- pulled_task = 1;
-
- /* Is there a task of a high priority class? */
- if (this_rq->nr_running != this_rq->cfs.h_nr_running)
- pulled_task = -1;
+ if (new_tasks < 0)
+ return RETRY_TASK;
-out:
- /* Move the next balance forward */
- if (time_after(this_rq->next_balance, next_balance))
- this_rq->next_balance = next_balance;
+ if (new_tasks > 0)
+ goto again;
- if (pulled_task)
- this_rq->idle_stamp = 0;
- else
- nohz_newidle_balance(this_rq);
+ /*
+ * rq is about to be idle, check if we need to update the
+ * lost_idle_time of clock_pelt
+ */
+ update_idle_rq_clock_pelt(rq);
- rq_repin_lock(this_rq, rf);
+ return NULL;
+}
- return pulled_task;
+static struct task_struct *__pick_next_task_fair(struct rq *rq)
+{
+ return pick_next_task_fair(rq, NULL, NULL);
}
/*
- * This softirq handler is triggered via SCHED_SOFTIRQ from two places:
- *
- * - directly from the local scheduler_tick() for periodic load balancing
- *
- * - indirectly from a remote scheduler_tick() for NOHZ idle balancing
- * through the SMP cross-call nohz_csd_func()
+ * Account for a descheduled task:
*/
-static __latent_entropy void sched_balance_softirq(struct softirq_action *h)
+static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
{
- struct rq *this_rq = this_rq();
- enum cpu_idle_type idle = this_rq->idle_balance;
- /*
- * If this CPU has a pending NOHZ_BALANCE_KICK, then do the
- * balancing on behalf of the other idle CPUs whose ticks are
- * stopped. Do nohz_idle_balance *before* sched_balance_domains to
- * give the idle CPUs a chance to load balance. Else we may
- * load balance only within the local sched_domain hierarchy
- * and abort nohz_idle_balance altogether if we pull some load.
- */
- if (nohz_idle_balance(this_rq, idle))
- return;
+ struct sched_entity *se = &prev->se;
+ struct cfs_rq *cfs_rq;
- /* normal load balance */
- sched_balance_update_blocked_averages(this_rq->cpu);
- sched_balance_domains(this_rq, idle);
+ for_each_sched_entity(se) {
+ cfs_rq = cfs_rq_of(se);
+ put_prev_entity(cfs_rq, se);
+ }
}
/*
- * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
+ * sched_yield() is very simple
*/
-void sched_balance_trigger(struct rq *rq)
+static void yield_task_fair(struct rq *rq)
{
+ struct task_struct *curr = rq->curr;
+ struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+ struct sched_entity *se = &curr->se;
+
/*
- * Don't need to rebalance while attached to NULL domain or
- * runqueue CPU is not active
+ * Are we the only task in the tree?
*/
- if (unlikely(on_null_domain(rq) || !cpu_active(cpu_of(rq))))
+ if (unlikely(rq->nr_running == 1))
return;
- if (time_after_eq(jiffies, rq->next_balance))
- raise_softirq(SCHED_SOFTIRQ);
+ clear_buddies(cfs_rq, se);
+
+ update_rq_clock(rq);
+ /*
+ * Update run-time statistics of the 'current'.
+ */
+ update_curr(cfs_rq);
+ /*
+ * Tell update_rq_clock() that we've just updated,
+ * so we don't do microscopic update in schedule()
+ * and double the fastpath cost.
+ */
+ rq_clock_skip_update(rq);
+
+ se->deadline += calc_delta_fair(se->slice, se);
+}
+
+static bool yield_to_task_fair(struct rq *rq, struct task_struct *p)
+{
+ struct sched_entity *se = &p->se;
+
+ /* throttled hierarchies are not runnable */
+ if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
+ return false;
+
+ /* Tell the scheduler that we'd really like se to run next. */
+ set_next_buddy(se);
+
+ yield_task_fair(rq);
- nohz_balancer_kick(rq);
+ return true;
}
+#ifdef CONFIG_SMP
+
static void rq_online_fair(struct rq *rq)
{
update_sysctl();
@@ -13272,24 +8014,12 @@ __init void init_sched_fair_class(void)
int i;
for_each_possible_cpu(i) {
- zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i), GFP_KERNEL, cpu_to_node(i));
zalloc_cpumask_var_node(&per_cpu(select_rq_mask, i), GFP_KERNEL, cpu_to_node(i));
- zalloc_cpumask_var_node(&per_cpu(should_we_balance_tmpmask, i),
- GFP_KERNEL, cpu_to_node(i));
#ifdef CONFIG_CFS_BANDWIDTH
INIT_CSD(&cpu_rq(i)->cfsb_csd, __cfsb_csd_unthrottle, cpu_rq(i));
INIT_LIST_HEAD(&cpu_rq(i)->cfsb_csd_list);
#endif
}
-
- open_softirq(SCHED_SOFTIRQ, sched_balance_softirq);
-
-#ifdef CONFIG_NO_HZ_COMMON
- nohz.next_balance = jiffies;
- nohz.next_blocked = jiffies;
- zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
-#endif
#endif /* SMP */
-
}
diff --git a/kernel/sched/fair_balance.c b/kernel/sched/fair_balance.c
new file mode 100644
index 000000000000..23b81a526160
--- /dev/null
+++ b/kernel/sched/fair_balance.c
@@ -0,0 +1,5103 @@
+#include <linux/sched.h>
+#include <linux/sched/clock.h>
+#include <linux/sched/isolation.h>
+#include <linux/sched/nohz.h>
+
+#include "sched.h"
+#include "pelt.h"
+
+#ifdef CONFIG_SMP
+
+/* Working cpumask for: sched_balance_rq(), sched_balance_newidle(). */
+static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
+static DEFINE_PER_CPU(cpumask_var_t, should_we_balance_tmpmask);
+
+#ifdef CONFIG_NO_HZ_COMMON
+
+static struct {
+ cpumask_var_t idle_cpus_mask;
+ atomic_t nr_cpus;
+ int has_blocked; /* Idle CPUS has blocked load */
+ int needs_update; /* Newly idle CPUs need their next_balance collated */
+ unsigned long next_balance; /* in jiffy units */
+ unsigned long next_blocked; /* Next update of blocked load in jiffies */
+} nohz ____cacheline_aligned;
+
+#endif /* CONFIG_NO_HZ_COMMON */
+
+/*
+ * cpu_load_without - compute CPU load without any contributions from *p
+ * @cpu: the CPU which load is requested
+ * @p: the task which load should be discounted
+ *
+ * The load of a CPU is defined by the load of tasks currently enqueued on that
+ * CPU as well as tasks which are currently sleeping after an execution on that
+ * CPU.
+ *
+ * This method returns the load of the specified CPU by discounting the load of
+ * the specified task, whenever the task is currently contributing to the CPU
+ * load.
+ */
+unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
+{
+ struct cfs_rq *cfs_rq;
+ unsigned int load;
+
+ /* Task has no contribution or is new */
+ if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
+ return cpu_load(rq);
+
+ cfs_rq = &rq->cfs;
+ load = READ_ONCE(cfs_rq->avg.load_avg);
+
+ /* Discount task's util from CPU's util */
+ lsub_positive(&load, task_h_load(p));
+
+ return load;
+}
+
+
+
+void enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ cfs_rq->avg.load_avg += se->avg.load_avg;
+ cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
+}
+
+void dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
+ sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
+ /* See update_cfs_rq_load_avg() */
+ cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum,
+ cfs_rq->avg.load_avg * PELT_MIN_DIVIDER);
+}
+
+#endif /* CONFIG_SMP */
+
+void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
+{
+ struct rq *rq = rq_of(cfs_rq);
+
+ if (&rq->cfs == cfs_rq) {
+ /*
+ * There are a few boundary cases this might miss but it should
+ * get called often enough that that should (hopefully) not be
+ * a real problem.
+ *
+ * It will not get called when we go idle, because the idle
+ * thread is a different class (!fair), nor will the utilization
+ * number include things like RT tasks.
+ *
+ * As is, the util number is not freq-invariant (we'd have to
+ * implement arch_scale_freq_capacity() for that).
+ *
+ * See cpu_util_cfs().
+ */
+ cpufreq_update_util(rq, flags);
+ }
+}
+
+#ifdef CONFIG_SMP
+static inline bool load_avg_is_decayed(struct sched_avg *sa)
+{
+ if (sa->load_sum)
+ return false;
+
+ if (sa->util_sum)
+ return false;
+
+ if (sa->runnable_sum)
+ return false;
+
+ /*
+ * _avg must be null when _sum are null because _avg = _sum / divider
+ * Make sure that rounding and/or propagation of PELT values never
+ * break this.
+ */
+ SCHED_WARN_ON(sa->load_avg ||
+ sa->util_avg ||
+ sa->runnable_avg);
+
+ return true;
+}
+
+static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
+{
+ return u64_u32_load_copy(cfs_rq->avg.last_update_time,
+ cfs_rq->last_update_time_copy);
+}
+#ifdef CONFIG_FAIR_GROUP_SCHED
+/*
+ * Because list_add_leaf_cfs_rq always places a child cfs_rq on the list
+ * immediately before a parent cfs_rq, and cfs_rqs are removed from the list
+ * bottom-up, we only have to test whether the cfs_rq before us on the list
+ * is our child.
+ * If cfs_rq is not on the list, test whether a child needs its to be added to
+ * connect a branch to the tree * (see list_add_leaf_cfs_rq() for details).
+ */
+static inline bool child_cfs_rq_on_list(struct cfs_rq *cfs_rq)
+{
+ struct cfs_rq *prev_cfs_rq;
+ struct list_head *prev;
+
+ if (cfs_rq->on_list) {
+ prev = cfs_rq->leaf_cfs_rq_list.prev;
+ } else {
+ struct rq *rq = rq_of(cfs_rq);
+
+ prev = rq->tmp_alone_branch;
+ }
+
+ prev_cfs_rq = container_of(prev, struct cfs_rq, leaf_cfs_rq_list);
+
+ return (prev_cfs_rq->tg->parent == cfs_rq->tg);
+}
+
+bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
+{
+ if (cfs_rq->load.weight)
+ return false;
+
+ if (!load_avg_is_decayed(&cfs_rq->avg))
+ return false;
+
+ if (child_cfs_rq_on_list(cfs_rq))
+ return false;
+
+ return true;
+}
+
+/**
+ * update_tg_load_avg - update the tg's load avg
+ * @cfs_rq: the cfs_rq whose avg changed
+ *
+ * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
+ * However, because tg->load_avg is a global value there are performance
+ * considerations.
+ *
+ * In order to avoid having to look at the other cfs_rq's, we use a
+ * differential update where we store the last value we propagated. This in
+ * turn allows skipping updates if the differential is 'small'.
+ *
+ * Updating tg's load_avg is necessary before update_cfs_share().
+ */
+void update_tg_load_avg(struct cfs_rq *cfs_rq)
+{
+ long delta;
+ u64 now;
+
+ /*
+ * No need to update load_avg for root_task_group as it is not used.
+ */
+ if (cfs_rq->tg == &root_task_group)
+ return;
+
+ /* rq has been offline and doesn't contribute to the share anymore: */
+ if (!cpu_active(cpu_of(rq_of(cfs_rq))))
+ return;
+
+ /*
+ * For migration heavy workloads, access to tg->load_avg can be
+ * unbound. Limit the update rate to at most once per ms.
+ */
+ now = sched_clock_cpu(cpu_of(rq_of(cfs_rq)));
+ if (now - cfs_rq->last_update_tg_load_avg < NSEC_PER_MSEC)
+ return;
+
+ delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
+ if (abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
+ atomic_long_add(delta, &cfs_rq->tg->load_avg);
+ cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
+ cfs_rq->last_update_tg_load_avg = now;
+ }
+}
+
+static inline void clear_tg_load_avg(struct cfs_rq *cfs_rq)
+{
+ long delta;
+ u64 now;
+
+ /*
+ * No need to update load_avg for root_task_group, as it is not used.
+ */
+ if (cfs_rq->tg == &root_task_group)
+ return;
+
+ now = sched_clock_cpu(cpu_of(rq_of(cfs_rq)));
+ delta = 0 - cfs_rq->tg_load_avg_contrib;
+ atomic_long_add(delta, &cfs_rq->tg->load_avg);
+ cfs_rq->tg_load_avg_contrib = 0;
+ cfs_rq->last_update_tg_load_avg = now;
+}
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+
+/* CPU offline callback: */
+void clear_tg_offline_cfs_rqs(struct rq *rq)
+{
+ struct task_group *tg;
+
+ lockdep_assert_rq_held(rq);
+
+ /*
+ * The rq clock has already been updated in
+ * set_rq_offline(), so we should skip updating
+ * the rq clock again in unthrottle_cfs_rq().
+ */
+ rq_clock_start_loop_update(rq);
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(tg, &task_groups, list) {
+ struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
+
+ clear_tg_load_avg(cfs_rq);
+ }
+ rcu_read_unlock();
+
+ rq_clock_stop_loop_update(rq);
+}
+
+#else /* !CONFIG_FAIR_GROUP_SCHED: */
+static inline void clear_tg_offline_cfs_rqs(struct rq *rq) {}
+#endif
+
+/*
+ * Called within set_task_rq() right before setting a task's CPU. The
+ * caller only guarantees p->pi_lock is held; no other assumptions,
+ * including the state of rq->lock, should be made.
+ */
+void set_task_rq_fair(struct sched_entity *se,
+ struct cfs_rq *prev, struct cfs_rq *next)
+{
+ u64 p_last_update_time;
+ u64 n_last_update_time;
+
+ if (!sched_feat(ATTACH_AGE_LOAD))
+ return;
+
+ /*
+ * We are supposed to update the task to "current" time, then its up to
+ * date and ready to go to new CPU/cfs_rq. But we have difficulty in
+ * getting what current time is, so simply throw away the out-of-date
+ * time. This will result in the wakee task is less decayed, but giving
+ * the wakee more load sounds not bad.
+ */
+ if (!(se->avg.last_update_time && prev))
+ return;
+
+ p_last_update_time = cfs_rq_last_update_time(prev);
+ n_last_update_time = cfs_rq_last_update_time(next);
+
+ __update_load_avg_blocked_se(p_last_update_time, se);
+ se->avg.last_update_time = n_last_update_time;
+}
+
+/*
+ * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
+ * propagate its contribution. The key to this propagation is the invariant
+ * that for each group:
+ *
+ * ge->avg == grq->avg (1)
+ *
+ * _IFF_ we look at the pure running and runnable sums. Because they
+ * represent the very same entity, just at different points in the hierarchy.
+ *
+ * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
+ * and simply copies the running/runnable sum over (but still wrong, because
+ * the group entity and group rq do not have their PELT windows aligned).
+ *
+ * However, update_tg_cfs_load() is more complex. So we have:
+ *
+ * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
+ *
+ * And since, like util, the runnable part should be directly transferable,
+ * the following would _appear_ to be the straight forward approach:
+ *
+ * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
+ *
+ * And per (1) we have:
+ *
+ * ge->avg.runnable_avg == grq->avg.runnable_avg
+ *
+ * Which gives:
+ *
+ * ge->load.weight * grq->avg.load_avg
+ * ge->avg.load_avg = ----------------------------------- (4)
+ * grq->load.weight
+ *
+ * Except that is wrong!
+ *
+ * Because while for entities historical weight is not important and we
+ * really only care about our future and therefore can consider a pure
+ * runnable sum, runqueues can NOT do this.
+ *
+ * We specifically want runqueues to have a load_avg that includes
+ * historical weights. Those represent the blocked load, the load we expect
+ * to (shortly) return to us. This only works by keeping the weights as
+ * integral part of the sum. We therefore cannot decompose as per (3).
+ *
+ * Another reason this doesn't work is that runnable isn't a 0-sum entity.
+ * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
+ * rq itself is runnable anywhere between 2/3 and 1 depending on how the
+ * runnable section of these tasks overlap (or not). If they were to perfectly
+ * align the rq as a whole would be runnable 2/3 of the time. If however we
+ * always have at least 1 runnable task, the rq as a whole is always runnable.
+ *
+ * So we'll have to approximate.. :/
+ *
+ * Given the constraint:
+ *
+ * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
+ *
+ * We can construct a rule that adds runnable to a rq by assuming minimal
+ * overlap.
+ *
+ * On removal, we'll assume each task is equally runnable; which yields:
+ *
+ * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
+ *
+ * XXX: only do this for the part of runnable > running ?
+ *
+ */
+static inline void
+update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
+{
+ long delta_sum, delta_avg = gcfs_rq->avg.util_avg - se->avg.util_avg;
+ u32 new_sum, divider;
+
+ /* Nothing to update */
+ if (!delta_avg)
+ return;
+
+ /*
+ * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
+ * See ___update_load_avg() for details.
+ */
+ divider = get_pelt_divider(&cfs_rq->avg);
+
+
+ /* Set new sched_entity's utilization */
+ se->avg.util_avg = gcfs_rq->avg.util_avg;
+ new_sum = se->avg.util_avg * divider;
+ delta_sum = (long)new_sum - (long)se->avg.util_sum;
+ se->avg.util_sum = new_sum;
+
+ /* Update parent cfs_rq utilization */
+ add_positive(&cfs_rq->avg.util_avg, delta_avg);
+ add_positive(&cfs_rq->avg.util_sum, delta_sum);
+
+ /* See update_cfs_rq_load_avg() */
+ cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
+ cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
+}
+
+static inline void
+update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
+{
+ long delta_sum, delta_avg = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
+ u32 new_sum, divider;
+
+ /* Nothing to update */
+ if (!delta_avg)
+ return;
+
+ /*
+ * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
+ * See ___update_load_avg() for details.
+ */
+ divider = get_pelt_divider(&cfs_rq->avg);
+
+ /* Set new sched_entity's runnable */
+ se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
+ new_sum = se->avg.runnable_avg * divider;
+ delta_sum = (long)new_sum - (long)se->avg.runnable_sum;
+ se->avg.runnable_sum = new_sum;
+
+ /* Update parent cfs_rq runnable */
+ add_positive(&cfs_rq->avg.runnable_avg, delta_avg);
+ add_positive(&cfs_rq->avg.runnable_sum, delta_sum);
+ /* See update_cfs_rq_load_avg() */
+ cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum,
+ cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER);
+}
+
+static inline void
+update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
+{
+ long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
+ unsigned long load_avg;
+ u64 load_sum = 0;
+ s64 delta_sum;
+ u32 divider;
+
+ if (!runnable_sum)
+ return;
+
+ gcfs_rq->prop_runnable_sum = 0;
+
+ /*
+ * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
+ * See ___update_load_avg() for details.
+ */
+ divider = get_pelt_divider(&cfs_rq->avg);
+
+ if (runnable_sum >= 0) {
+ /*
+ * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
+ * the CPU is saturated running == runnable.
+ */
+ runnable_sum += se->avg.load_sum;
+ runnable_sum = min_t(long, runnable_sum, divider);
+ } else {
+ /*
+ * Estimate the new unweighted runnable_sum of the gcfs_rq by
+ * assuming all tasks are equally runnable.
+ */
+ if (scale_load_down(gcfs_rq->load.weight)) {
+ load_sum = div_u64(gcfs_rq->avg.load_sum,
+ scale_load_down(gcfs_rq->load.weight));
+ }
+
+ /* But make sure to not inflate se's runnable */
+ runnable_sum = min(se->avg.load_sum, load_sum);
+ }
+
+ /*
+ * runnable_sum can't be lower than running_sum
+ * Rescale running sum to be in the same range as runnable sum
+ * running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT]
+ * runnable_sum is in [0 : LOAD_AVG_MAX]
+ */
+ running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
+ runnable_sum = max(runnable_sum, running_sum);
+
+ load_sum = se_weight(se) * runnable_sum;
+ load_avg = div_u64(load_sum, divider);
+
+ delta_avg = load_avg - se->avg.load_avg;
+ if (!delta_avg)
+ return;
+
+ delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
+
+ se->avg.load_sum = runnable_sum;
+ se->avg.load_avg = load_avg;
+ add_positive(&cfs_rq->avg.load_avg, delta_avg);
+ add_positive(&cfs_rq->avg.load_sum, delta_sum);
+ /* See update_cfs_rq_load_avg() */
+ cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum,
+ cfs_rq->avg.load_avg * PELT_MIN_DIVIDER);
+}
+
+static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
+{
+ cfs_rq->propagate = 1;
+ cfs_rq->prop_runnable_sum += runnable_sum;
+}
+
+/* Update task and its cfs_rq load average */
+static inline int propagate_entity_load_avg(struct sched_entity *se)
+{
+ struct cfs_rq *cfs_rq, *gcfs_rq;
+
+ if (entity_is_task(se))
+ return 0;
+
+ gcfs_rq = group_cfs_rq(se);
+ if (!gcfs_rq->propagate)
+ return 0;
+
+ gcfs_rq->propagate = 0;
+
+ cfs_rq = cfs_rq_of(se);
+
+ add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
+
+ update_tg_cfs_util(cfs_rq, se, gcfs_rq);
+ update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
+ update_tg_cfs_load(cfs_rq, se, gcfs_rq);
+
+ trace_pelt_cfs_tp(cfs_rq);
+ trace_pelt_se_tp(se);
+
+ return 1;
+}
+
+/*
+ * Check if we need to update the load and the utilization of a blocked
+ * group_entity:
+ */
+static inline bool skip_blocked_update(struct sched_entity *se)
+{
+ struct cfs_rq *gcfs_rq = group_cfs_rq(se);
+
+ /*
+ * If sched_entity still have not zero load or utilization, we have to
+ * decay it:
+ */
+ if (se->avg.load_avg || se->avg.util_avg)
+ return false;
+
+ /*
+ * If there is a pending propagation, we have to update the load and
+ * the utilization of the sched_entity:
+ */
+ if (gcfs_rq->propagate)
+ return false;
+
+ /*
+ * Otherwise, the load and the utilization of the sched_entity is
+ * already zero and there is no pending propagation, so it will be a
+ * waste of time to try to decay it:
+ */
+ return true;
+}
+
+#else /* CONFIG_FAIR_GROUP_SCHED */
+
+static inline int propagate_entity_load_avg(struct sched_entity *se)
+{
+ return 0;
+}
+
+static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
+
+#endif /* CONFIG_FAIR_GROUP_SCHED */
+
+#ifdef CONFIG_NO_HZ_COMMON
+void migrate_se_pelt_lag(struct sched_entity *se)
+{
+ u64 throttled = 0, now, lut;
+ struct cfs_rq *cfs_rq;
+ struct rq *rq;
+ bool is_idle;
+
+ if (load_avg_is_decayed(&se->avg))
+ return;
+
+ cfs_rq = cfs_rq_of(se);
+ rq = rq_of(cfs_rq);
+
+ rcu_read_lock();
+ is_idle = is_idle_task(rcu_dereference(rq->curr));
+ rcu_read_unlock();
+
+ /*
+ * The lag estimation comes with a cost we don't want to pay all the
+ * time. Hence, limiting to the case where the source CPU is idle and
+ * we know we are at the greatest risk to have an outdated clock.
+ */
+ if (!is_idle)
+ return;
+
+ /*
+ * Estimated "now" is: last_update_time + cfs_idle_lag + rq_idle_lag, where:
+ *
+ * last_update_time (the cfs_rq's last_update_time)
+ * = cfs_rq_clock_pelt()@cfs_rq_idle
+ * = rq_clock_pelt()@cfs_rq_idle
+ * - cfs->throttled_clock_pelt_time@..._rq_idle
+ *
+ * cfs_idle_lag (delta between rq's update and cfs_rq's update)
+ * = rq_clock_pelt()@rq_idle - rq_clock_pelt()@cfs_rq_idle
+ *
+ * rq_idle_lag (delta between now and rq's update)
+ * = sched_clock_cpu() - rq_clock()@rq_idle
+ *
+ * We can then write:
+ *
+ * now = rq_clock_pelt()@rq_idle - cfs->throttled_clock_pelt_time +
+ * sched_clock_cpu() - rq_clock()@rq_idle
+ * Where:
+ * rq_clock_pelt()@rq_idle is rq->clock_pelt_idle
+ * rq_clock()@rq_idle is rq->clock_idle
+ * cfs->throttled_clock_pelt_time@..._rq_idle
+ * is cfs_rq->throttled_pelt_idle
+ */
+
+#ifdef CONFIG_CFS_BANDWIDTH
+ throttled = u64_u32_load(cfs_rq->throttled_pelt_idle);
+ /* The clock has been stopped for throttling */
+ if (throttled == U64_MAX)
+ return;
+#endif
+ now = u64_u32_load(rq->clock_pelt_idle);
+ /*
+ * Paired with _update_idle_rq_clock_pelt(). It ensures at the worst case
+ * is observed the old clock_pelt_idle value and the new clock_idle,
+ * which lead to an underestimation. The opposite would lead to an
+ * overestimation.
+ */
+ smp_rmb();
+ lut = cfs_rq_last_update_time(cfs_rq);
+
+ now -= throttled;
+ if (now < lut)
+ /*
+ * cfs_rq->avg.last_update_time is more recent than our
+ * estimation, let's use it.
+ */
+ now = lut;
+ else
+ now += sched_clock_cpu(cpu_of(rq)) - u64_u32_load(rq->clock_idle);
+
+ __update_load_avg_blocked_se(now, se);
+}
+#endif
+
+/**
+ * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
+ * @now: current time, as per cfs_rq_clock_pelt()
+ * @cfs_rq: cfs_rq to update
+ *
+ * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
+ * avg. The immediate corollary is that all (fair) tasks must be attached.
+ *
+ * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
+ *
+ * Return: true if the load decayed or we removed load.
+ *
+ * Since both these conditions indicate a changed cfs_rq->avg.load we should
+ * call update_tg_load_avg() when this function returns true.
+ */
+static inline int
+update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
+{
+ unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0;
+ struct sched_avg *sa = &cfs_rq->avg;
+ int decayed = 0;
+
+ if (cfs_rq->removed.nr) {
+ unsigned long r;
+ u32 divider = get_pelt_divider(&cfs_rq->avg);
+
+ raw_spin_lock(&cfs_rq->removed.lock);
+ swap(cfs_rq->removed.util_avg, removed_util);
+ swap(cfs_rq->removed.load_avg, removed_load);
+ swap(cfs_rq->removed.runnable_avg, removed_runnable);
+ cfs_rq->removed.nr = 0;
+ raw_spin_unlock(&cfs_rq->removed.lock);
+
+ r = removed_load;
+ sub_positive(&sa->load_avg, r);
+ sub_positive(&sa->load_sum, r * divider);
+ /* See sa->util_sum below */
+ sa->load_sum = max_t(u32, sa->load_sum, sa->load_avg * PELT_MIN_DIVIDER);
+
+ r = removed_util;
+ sub_positive(&sa->util_avg, r);
+ sub_positive(&sa->util_sum, r * divider);
+ /*
+ * Because of rounding, se->util_sum might ends up being +1 more than
+ * cfs->util_sum. Although this is not a problem by itself, detaching
+ * a lot of tasks with the rounding problem between 2 updates of
+ * util_avg (~1ms) can make cfs->util_sum becoming null whereas
+ * cfs_util_avg is not.
+ * Check that util_sum is still above its lower bound for the new
+ * util_avg. Given that period_contrib might have moved since the last
+ * sync, we are only sure that util_sum must be above or equal to
+ * util_avg * minimum possible divider
+ */
+ sa->util_sum = max_t(u32, sa->util_sum, sa->util_avg * PELT_MIN_DIVIDER);
+
+ r = removed_runnable;
+ sub_positive(&sa->runnable_avg, r);
+ sub_positive(&sa->runnable_sum, r * divider);
+ /* See sa->util_sum above */
+ sa->runnable_sum = max_t(u32, sa->runnable_sum,
+ sa->runnable_avg * PELT_MIN_DIVIDER);
+
+ /*
+ * removed_runnable is the unweighted version of removed_load so we
+ * can use it to estimate removed_load_sum.
+ */
+ add_tg_cfs_propagate(cfs_rq,
+ -(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT);
+
+ decayed = 1;
+ }
+
+ decayed |= __update_load_avg_cfs_rq(now, cfs_rq);
+ u64_u32_store_copy(sa->last_update_time,
+ cfs_rq->last_update_time_copy,
+ sa->last_update_time);
+ return decayed;
+}
+
+/**
+ * attach_entity_load_avg - attach this entity to its cfs_rq load avg
+ * @cfs_rq: cfs_rq to attach to
+ * @se: sched_entity to attach
+ *
+ * Must call update_cfs_rq_load_avg() before this, since we rely on
+ * cfs_rq->avg.last_update_time being current.
+ */
+void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ /*
+ * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
+ * See ___update_load_avg() for details.
+ */
+ u32 divider = get_pelt_divider(&cfs_rq->avg);
+
+ /*
+ * When we attach the @se to the @cfs_rq, we must align the decay
+ * window because without that, really weird and wonderful things can
+ * happen.
+ *
+ * XXX illustrate
+ */
+ se->avg.last_update_time = cfs_rq->avg.last_update_time;
+ se->avg.period_contrib = cfs_rq->avg.period_contrib;
+
+ /*
+ * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
+ * period_contrib. This isn't strictly correct, but since we're
+ * entirely outside of the PELT hierarchy, nobody cares if we truncate
+ * _sum a little.
+ */
+ se->avg.util_sum = se->avg.util_avg * divider;
+
+ se->avg.runnable_sum = se->avg.runnable_avg * divider;
+
+ se->avg.load_sum = se->avg.load_avg * divider;
+ if (se_weight(se) < se->avg.load_sum)
+ se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se));
+ else
+ se->avg.load_sum = 1;
+
+ enqueue_load_avg(cfs_rq, se);
+ cfs_rq->avg.util_avg += se->avg.util_avg;
+ cfs_rq->avg.util_sum += se->avg.util_sum;
+ cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
+ cfs_rq->avg.runnable_sum += se->avg.runnable_sum;
+
+ add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
+
+ cfs_rq_util_change(cfs_rq, 0);
+
+ trace_pelt_cfs_tp(cfs_rq);
+}
+
+/**
+ * detach_entity_load_avg - detach this entity from its cfs_rq load avg
+ * @cfs_rq: cfs_rq to detach from
+ * @se: sched_entity to detach
+ *
+ * Must call update_cfs_rq_load_avg() before this, since we rely on
+ * cfs_rq->avg.last_update_time being current.
+ */
+void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ dequeue_load_avg(cfs_rq, se);
+ sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
+ sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
+ /* See update_cfs_rq_load_avg() */
+ cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
+ cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
+
+ sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
+ sub_positive(&cfs_rq->avg.runnable_sum, se->avg.runnable_sum);
+ /* See update_cfs_rq_load_avg() */
+ cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum,
+ cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER);
+
+ add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
+
+ cfs_rq_util_change(cfs_rq, 0);
+
+ trace_pelt_cfs_tp(cfs_rq);
+}
+
+/* Update task and its cfs_rq load average */
+void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
+{
+ u64 now = cfs_rq_clock_pelt(cfs_rq);
+ int decayed;
+
+ /*
+ * Track task load average for carrying it to new CPU after migrated, and
+ * track group sched_entity load average for task_h_load calculation in migration
+ */
+ if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
+ __update_load_avg_se(now, cfs_rq, se);
+
+ decayed = update_cfs_rq_load_avg(now, cfs_rq);
+ decayed |= propagate_entity_load_avg(se);
+
+ if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
+
+ /*
+ * DO_ATTACH means we're here from enqueue_entity().
+ * !last_update_time means we've passed through
+ * migrate_task_rq_fair() indicating we migrated.
+ *
+ * IOW we're enqueueing a task on a new CPU.
+ */
+ attach_entity_load_avg(cfs_rq, se);
+ update_tg_load_avg(cfs_rq);
+
+ } else if (flags & DO_DETACH) {
+ /*
+ * DO_DETACH means we're here from dequeue_entity()
+ * and we are migrating task out of the CPU.
+ */
+ detach_entity_load_avg(cfs_rq, se);
+ update_tg_load_avg(cfs_rq);
+ } else if (decayed) {
+ cfs_rq_util_change(cfs_rq, 0);
+
+ if (flags & UPDATE_TG)
+ update_tg_load_avg(cfs_rq);
+ }
+}
+
+/*
+ * Synchronize entity load avg of dequeued entity without locking
+ * the previous rq.
+ */
+void sync_entity_load_avg(struct sched_entity *se)
+{
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ u64 last_update_time;
+
+ last_update_time = cfs_rq_last_update_time(cfs_rq);
+ __update_load_avg_blocked_se(last_update_time, se);
+}
+
+/*
+ * Task first catches up with cfs_rq, and then subtract
+ * itself from the cfs_rq (task must be off the queue now).
+ */
+void remove_entity_load_avg(struct sched_entity *se)
+{
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ unsigned long flags;
+
+ /*
+ * tasks cannot exit without having gone through wake_up_new_task() ->
+ * enqueue_task_fair() which will have added things to the cfs_rq,
+ * so we can remove unconditionally.
+ */
+
+ sync_entity_load_avg(se);
+
+ raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
+ ++cfs_rq->removed.nr;
+ cfs_rq->removed.util_avg += se->avg.util_avg;
+ cfs_rq->removed.load_avg += se->avg.load_avg;
+ cfs_rq->removed.runnable_avg += se->avg.runnable_avg;
+ raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
+}
+
+static inline unsigned long task_runnable(struct task_struct *p)
+{
+ return READ_ONCE(p->se.avg.runnable_avg);
+}
+
+/*
+ * For asym packing, by default the lower numbered CPU has higher priority.
+ */
+int __weak arch_asym_cpu_priority(int cpu)
+{
+ return -cpu;
+}
+
+/*
+ * The margin used when comparing utilization with CPU capacity.
+ *
+ * (default: ~20%)
+ */
+#define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024)
+
+/*
+ * The margin used when comparing CPU capacities.
+ * is 'cap1' noticeably greater than 'cap2'
+ *
+ * (default: ~5%)
+ */
+#define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078)
+
+void util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p)
+{
+ unsigned int enqueued;
+
+ if (!sched_feat(UTIL_EST))
+ return;
+
+ /* Update root cfs_rq's estimated utilization */
+ enqueued = cfs_rq->avg.util_est;
+ enqueued += _task_util_est(p);
+ WRITE_ONCE(cfs_rq->avg.util_est, enqueued);
+
+ trace_sched_util_est_cfs_tp(cfs_rq);
+}
+
+void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p)
+{
+ unsigned int enqueued;
+
+ if (!sched_feat(UTIL_EST))
+ return;
+
+ /* Update root cfs_rq's estimated utilization */
+ enqueued = cfs_rq->avg.util_est;
+ enqueued -= min_t(unsigned int, enqueued, _task_util_est(p));
+ WRITE_ONCE(cfs_rq->avg.util_est, enqueued);
+
+ trace_sched_util_est_cfs_tp(cfs_rq);
+}
+
+#define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100)
+
+void util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
+{
+ unsigned int ewma, dequeued, last_ewma_diff;
+
+ if (!sched_feat(UTIL_EST))
+ return;
+
+ /*
+ * Skip update of task's estimated utilization when the task has not
+ * yet completed an activation, e.g. being migrated.
+ */
+ if (!task_sleep)
+ return;
+
+ /* Get current estimate of utilization */
+ ewma = READ_ONCE(p->se.avg.util_est);
+
+ /*
+ * If the PELT values haven't changed since enqueue time,
+ * skip the util_est update.
+ */
+ if (ewma & UTIL_AVG_UNCHANGED)
+ return;
+
+ /* Get utilization at dequeue */
+ dequeued = task_util(p);
+
+ /*
+ * Reset EWMA on utilization increases, the moving average is used only
+ * to smooth utilization decreases.
+ */
+ if (ewma <= dequeued) {
+ ewma = dequeued;
+ goto done;
+ }
+
+ /*
+ * Skip update of task's estimated utilization when its members are
+ * already ~1% close to its last activation value.
+ */
+ last_ewma_diff = ewma - dequeued;
+ if (last_ewma_diff < UTIL_EST_MARGIN)
+ goto done;
+
+ /*
+ * To avoid overestimation of actual task utilization, skip updates if
+ * we cannot grant there is idle time in this CPU.
+ */
+ if (dequeued > arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq))))
+ return;
+
+ /*
+ * To avoid underestimate of task utilization, skip updates of EWMA if
+ * we cannot grant that thread got all CPU time it wanted.
+ */
+ if ((dequeued + UTIL_EST_MARGIN) < task_runnable(p))
+ goto done;
+
+
+ /*
+ * Update Task's estimated utilization
+ *
+ * When *p completes an activation we can consolidate another sample
+ * of the task size. This is done by using this value to update the
+ * Exponential Weighted Moving Average (EWMA):
+ *
+ * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
+ * = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
+ * = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
+ * = w * ( -last_ewma_diff ) + ewma(t-1)
+ * = w * (-last_ewma_diff + ewma(t-1) / w)
+ *
+ * Where 'w' is the weight of new samples, which is configured to be
+ * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
+ */
+ ewma <<= UTIL_EST_WEIGHT_SHIFT;
+ ewma -= last_ewma_diff;
+ ewma >>= UTIL_EST_WEIGHT_SHIFT;
+done:
+ ewma |= UTIL_AVG_UNCHANGED;
+ WRITE_ONCE(p->se.avg.util_est, ewma);
+
+ trace_sched_util_est_se_tp(&p->se);
+}
+
+int util_fits_cpu(unsigned long util,
+ unsigned long uclamp_min,
+ unsigned long uclamp_max,
+ int cpu)
+{
+ unsigned long capacity_orig, capacity_orig_thermal;
+ unsigned long capacity = capacity_of(cpu);
+ bool fits, uclamp_max_fits;
+
+ /*
+ * Check if the real util fits without any uclamp boost/cap applied.
+ */
+ fits = fits_capacity(util, capacity);
+
+ if (!uclamp_is_used())
+ return fits;
+
+ /*
+ * We must use arch_scale_cpu_capacity() for comparing against uclamp_min and
+ * uclamp_max. We only care about capacity pressure (by using
+ * capacity_of()) for comparing against the real util.
+ *
+ * If a task is boosted to 1024 for example, we don't want a tiny
+ * pressure to skew the check whether it fits a CPU or not.
+ *
+ * Similarly if a task is capped to arch_scale_cpu_capacity(little_cpu), it
+ * should fit a little cpu even if there's some pressure.
+ *
+ * Only exception is for thermal pressure since it has a direct impact
+ * on available OPP of the system.
+ *
+ * We honour it for uclamp_min only as a drop in performance level
+ * could result in not getting the requested minimum performance level.
+ *
+ * For uclamp_max, we can tolerate a drop in performance level as the
+ * goal is to cap the task. So it's okay if it's getting less.
+ */
+ capacity_orig = arch_scale_cpu_capacity(cpu);
+ capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
+
+ /*
+ * We want to force a task to fit a cpu as implied by uclamp_max.
+ * But we do have some corner cases to cater for..
+ *
+ *
+ * C=z
+ * | ___
+ * | C=y | |
+ * |_ _ _ _ _ _ _ _ _ ___ _ _ _ | _ | _ _ _ _ _ uclamp_max
+ * | C=x | | | |
+ * | ___ | | | |
+ * | | | | | | | (util somewhere in this region)
+ * | | | | | | |
+ * | | | | | | |
+ * +----------------------------------------
+ * CPU0 CPU1 CPU2
+ *
+ * In the above example if a task is capped to a specific performance
+ * point, y, then when:
+ *
+ * * util = 80% of x then it does not fit on CPU0 and should migrate
+ * to CPU1
+ * * util = 80% of y then it is forced to fit on CPU1 to honour
+ * uclamp_max request.
+ *
+ * which is what we're enforcing here. A task always fits if
+ * uclamp_max <= capacity_orig. But when uclamp_max > capacity_orig,
+ * the normal upmigration rules should withhold still.
+ *
+ * Only exception is when we are on max capacity, then we need to be
+ * careful not to block overutilized state. This is so because:
+ *
+ * 1. There's no concept of capping at max_capacity! We can't go
+ * beyond this performance level anyway.
+ * 2. The system is being saturated when we're operating near
+ * max capacity, it doesn't make sense to block overutilized.
+ */
+ uclamp_max_fits = (capacity_orig == SCHED_CAPACITY_SCALE) && (uclamp_max == SCHED_CAPACITY_SCALE);
+ uclamp_max_fits = !uclamp_max_fits && (uclamp_max <= capacity_orig);
+ fits = fits || uclamp_max_fits;
+
+ /*
+ *
+ * C=z
+ * | ___ (region a, capped, util >= uclamp_max)
+ * | C=y | |
+ * |_ _ _ _ _ _ _ _ _ ___ _ _ _ | _ | _ _ _ _ _ uclamp_max
+ * | C=x | | | |
+ * | ___ | | | | (region b, uclamp_min <= util <= uclamp_max)
+ * |_ _ _|_ _|_ _ _ _| _ | _ _ _| _ | _ _ _ _ _ uclamp_min
+ * | | | | | | |
+ * | | | | | | | (region c, boosted, util < uclamp_min)
+ * +----------------------------------------
+ * CPU0 CPU1 CPU2
+ *
+ * a) If util > uclamp_max, then we're capped, we don't care about
+ * actual fitness value here. We only care if uclamp_max fits
+ * capacity without taking margin/pressure into account.
+ * See comment above.
+ *
+ * b) If uclamp_min <= util <= uclamp_max, then the normal
+ * fits_capacity() rules apply. Except we need to ensure that we
+ * enforce we remain within uclamp_max, see comment above.
+ *
+ * c) If util < uclamp_min, then we are boosted. Same as (b) but we
+ * need to take into account the boosted value fits the CPU without
+ * taking margin/pressure into account.
+ *
+ * Cases (a) and (b) are handled in the 'fits' variable already. We
+ * just need to consider an extra check for case (c) after ensuring we
+ * handle the case uclamp_min > uclamp_max.
+ */
+ uclamp_min = min(uclamp_min, uclamp_max);
+ if (fits && (util < uclamp_min) && (uclamp_min > capacity_orig_thermal))
+ return -1;
+
+ return fits;
+}
+
+static inline int task_fits_cpu(struct task_struct *p, int cpu)
+{
+ unsigned long uclamp_min = uclamp_eff_value(p, UCLAMP_MIN);
+ unsigned long uclamp_max = uclamp_eff_value(p, UCLAMP_MAX);
+ unsigned long util = task_util_est(p);
+ /*
+ * Return true only if the cpu fully fits the task requirements, which
+ * include the utilization but also the performance hints.
+ */
+ return (util_fits_cpu(util, uclamp_min, uclamp_max, cpu) > 0);
+}
+
+void update_misfit_status(struct task_struct *p, struct rq *rq)
+{
+ int cpu = cpu_of(rq);
+
+ if (!sched_asym_cpucap_active())
+ return;
+
+ /*
+ * Affinity allows us to go somewhere higher? Or are we on biggest
+ * available CPU already? Or do we fit into this CPU ?
+ */
+ if (!p || (p->nr_cpus_allowed == 1) ||
+ (arch_scale_cpu_capacity(cpu) == p->max_allowed_capacity) ||
+ task_fits_cpu(p, cpu)) {
+
+ rq->misfit_task_load = 0;
+ return;
+ }
+
+ /*
+ * Make sure that misfit_task_load will not be null even if
+ * task_h_load() returns 0.
+ */
+ rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1);
+}
+
+static inline bool cpu_overutilized(int cpu)
+{
+ unsigned long rq_util_min, rq_util_max;
+
+ if (!sched_energy_enabled())
+ return false;
+
+ rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
+ rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
+
+ /* Return true only if the utilization doesn't fit CPU's capacity */
+ return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
+}
+
+static inline void set_rd_overutilized(struct root_domain *rd, bool flag)
+{
+ if (!sched_energy_enabled())
+ return;
+
+ WRITE_ONCE(rd->overutilized, flag);
+ trace_sched_overutilized_tp(rd, flag);
+}
+
+void check_update_overutilized_status(struct rq *rq)
+{
+ /*
+ * overutilized field is used for load balancing decisions only
+ * if energy aware scheduler is being used
+ */
+
+ if (!is_rd_overutilized(rq->rd) && cpu_overutilized(rq->cpu))
+ set_rd_overutilized(rq->rd, 1);
+}
+
+/**************************************************
+ * Fair scheduling class load-balancing methods.
+ *
+ * BASICS
+ *
+ * The purpose of load-balancing is to achieve the same basic fairness the
+ * per-CPU scheduler provides, namely provide a proportional amount of compute
+ * time to each task. This is expressed in the following equation:
+ *
+ * W_i,n/P_i == W_j,n/P_j for all i,j (1)
+ *
+ * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
+ * W_i,0 is defined as:
+ *
+ * W_i,0 = \Sum_j w_i,j (2)
+ *
+ * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
+ * is derived from the nice value as per sched_prio_to_weight[].
+ *
+ * The weight average is an exponential decay average of the instantaneous
+ * weight:
+ *
+ * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
+ *
+ * C_i is the compute capacity of CPU i, typically it is the
+ * fraction of 'recent' time available for SCHED_OTHER task execution. But it
+ * can also include other factors [XXX].
+ *
+ * To achieve this balance we define a measure of imbalance which follows
+ * directly from (1):
+ *
+ * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
+ *
+ * We them move tasks around to minimize the imbalance. In the continuous
+ * function space it is obvious this converges, in the discrete case we get
+ * a few fun cases generally called infeasible weight scenarios.
+ *
+ * [XXX expand on:
+ * - infeasible weights;
+ * - local vs global optima in the discrete case. ]
+ *
+ *
+ * SCHED DOMAINS
+ *
+ * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
+ * for all i,j solution, we create a tree of CPUs that follows the hardware
+ * topology where each level pairs two lower groups (or better). This results
+ * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
+ * tree to only the first of the previous level and we decrease the frequency
+ * of load-balance at each level inv. proportional to the number of CPUs in
+ * the groups.
+ *
+ * This yields:
+ *
+ * log_2 n 1 n
+ * \Sum { --- * --- * 2^i } = O(n) (5)
+ * i = 0 2^i 2^i
+ * `- size of each group
+ * | | `- number of CPUs doing load-balance
+ * | `- freq
+ * `- sum over all levels
+ *
+ * Coupled with a limit on how many tasks we can migrate every balance pass,
+ * this makes (5) the runtime complexity of the balancer.
+ *
+ * An important property here is that each CPU is still (indirectly) connected
+ * to every other CPU in at most O(log n) steps:
+ *
+ * The adjacency matrix of the resulting graph is given by:
+ *
+ * log_2 n
+ * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
+ * k = 0
+ *
+ * And you'll find that:
+ *
+ * A^(log_2 n)_i,j != 0 for all i,j (7)
+ *
+ * Showing there's indeed a path between every CPU in at most O(log n) steps.
+ * The task movement gives a factor of O(m), giving a convergence complexity
+ * of:
+ *
+ * O(nm log n), n := nr_cpus, m := nr_tasks (8)
+ *
+ *
+ * WORK CONSERVING
+ *
+ * In order to avoid CPUs going idle while there's still work to do, new idle
+ * balancing is more aggressive and has the newly idle CPU iterate up the domain
+ * tree itself instead of relying on other CPUs to bring it work.
+ *
+ * This adds some complexity to both (5) and (8) but it reduces the total idle
+ * time.
+ *
+ * [XXX more?]
+ *
+ *
+ * CGROUPS
+ *
+ * Cgroups make a horror show out of (2), instead of a simple sum we get:
+ *
+ * s_k,i
+ * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
+ * S_k
+ *
+ * Where
+ *
+ * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
+ *
+ * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
+ *
+ * The big problem is S_k, its a global sum needed to compute a local (W_i)
+ * property.
+ *
+ * [XXX write more on how we solve this.. _after_ merging pjt's patches that
+ * rewrite all of this once again.]
+ */
+
+static unsigned long __read_mostly max_load_balance_interval = HZ/10;
+
+enum fbq_type { regular, remote, all };
+
+/*
+ * 'group_type' describes the group of CPUs at the moment of load balancing.
+ *
+ * The enum is ordered by pulling priority, with the group with lowest priority
+ * first so the group_type can simply be compared when selecting the busiest
+ * group. See update_sd_pick_busiest().
+ */
+enum group_type {
+ /* The group has spare capacity that can be used to run more tasks. */
+ group_has_spare = 0,
+ /*
+ * The group is fully used and the tasks don't compete for more CPU
+ * cycles. Nevertheless, some tasks might wait before running.
+ */
+ group_fully_busy,
+ /*
+ * One task doesn't fit with CPU's capacity and must be migrated to a
+ * more powerful CPU.
+ */
+ group_misfit_task,
+ /*
+ * Balance SMT group that's fully busy. Can benefit from migration
+ * a task on SMT with busy sibling to another CPU on idle core.
+ */
+ group_smt_balance,
+ /*
+ * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
+ * and the task should be migrated to it instead of running on the
+ * current CPU.
+ */
+ group_asym_packing,
+ /*
+ * The tasks' affinity constraints previously prevented the scheduler
+ * from balancing the load across the system.
+ */
+ group_imbalanced,
+ /*
+ * The CPU is overloaded and can't provide expected CPU cycles to all
+ * tasks.
+ */
+ group_overloaded
+};
+
+enum migration_type {
+ migrate_load = 0,
+ migrate_util,
+ migrate_task,
+ migrate_misfit
+};
+
+#define LBF_ALL_PINNED 0x01
+#define LBF_NEED_BREAK 0x02
+#define LBF_DST_PINNED 0x04
+#define LBF_SOME_PINNED 0x08
+#define LBF_ACTIVE_LB 0x10
+
+struct lb_env {
+ struct sched_domain *sd;
+
+ struct rq *src_rq;
+ int src_cpu;
+
+ int dst_cpu;
+ struct rq *dst_rq;
+
+ struct cpumask *dst_grpmask;
+ int new_dst_cpu;
+ enum cpu_idle_type idle;
+ long imbalance;
+ /* The set of CPUs under consideration for load-balancing */
+ struct cpumask *cpus;
+
+ unsigned int flags;
+
+ unsigned int loop;
+ unsigned int loop_break;
+ unsigned int loop_max;
+
+ enum fbq_type fbq_type;
+ enum migration_type migration_type;
+ struct list_head tasks;
+};
+
+/*
+ * Is this task likely cache-hot:
+ */
+static int task_hot(struct task_struct *p, struct lb_env *env)
+{
+ s64 delta;
+
+ lockdep_assert_rq_held(env->src_rq);
+
+ if (p->sched_class != &fair_sched_class)
+ return 0;
+
+ if (unlikely(task_has_idle_policy(p)))
+ return 0;
+
+ /* SMT siblings share cache */
+ if (env->sd->flags & SD_SHARE_CPUCAPACITY)
+ return 0;
+
+ /*
+ * Buddy candidates are cache hot:
+ */
+ if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
+ (&p->se == cfs_rq_of(&p->se)->next))
+ return 1;
+
+ if (sysctl_sched_migration_cost == -1)
+ return 1;
+
+ /*
+ * Don't migrate task if the task's cookie does not match
+ * with the destination CPU's core cookie.
+ */
+ if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p))
+ return 1;
+
+ if (sysctl_sched_migration_cost == 0)
+ return 0;
+
+ delta = rq_clock_task(env->src_rq) - p->se.exec_start;
+
+ return delta < (s64)sysctl_sched_migration_cost;
+}
+
+#ifdef CONFIG_NUMA_BALANCING
+/*
+ * Returns 1, if task migration degrades locality
+ * Returns 0, if task migration improves locality i.e migration preferred.
+ * Returns -1, if task migration is not affected by locality.
+ */
+static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
+{
+ struct numa_group *numa_group = rcu_dereference(p->numa_group);
+ unsigned long src_weight, dst_weight;
+ int src_nid, dst_nid, dist;
+
+ if (!static_branch_likely(&sched_numa_balancing))
+ return -1;
+
+ if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
+ return -1;
+
+ src_nid = cpu_to_node(env->src_cpu);
+ dst_nid = cpu_to_node(env->dst_cpu);
+
+ if (src_nid == dst_nid)
+ return -1;
+
+ /* Migrating away from the preferred node is always bad. */
+ if (src_nid == p->numa_preferred_nid) {
+ if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
+ return 1;
+ else
+ return -1;
+ }
+
+ /* Encourage migration to the preferred node. */
+ if (dst_nid == p->numa_preferred_nid)
+ return 0;
+
+ /* Leaving a core idle is often worse than degrading locality. */
+ if (env->idle == CPU_IDLE)
+ return -1;
+
+ dist = node_distance(src_nid, dst_nid);
+ if (numa_group) {
+ src_weight = group_weight(p, src_nid, dist);
+ dst_weight = group_weight(p, dst_nid, dist);
+ } else {
+ src_weight = task_weight(p, src_nid, dist);
+ dst_weight = task_weight(p, dst_nid, dist);
+ }
+
+ return dst_weight < src_weight;
+}
+
+#else
+static inline int migrate_degrades_locality(struct task_struct *p,
+ struct lb_env *env)
+{
+ return -1;
+}
+#endif
+
+/*
+ * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
+ */
+static
+int can_migrate_task(struct task_struct *p, struct lb_env *env)
+{
+ int tsk_cache_hot;
+
+ lockdep_assert_rq_held(env->src_rq);
+
+ /*
+ * We do not migrate tasks that are:
+ * 1) throttled_lb_pair, or
+ * 2) cannot be migrated to this CPU due to cpus_ptr, or
+ * 3) running (obviously), or
+ * 4) are cache-hot on their current CPU.
+ */
+ if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
+ return 0;
+
+ /* Disregard percpu kthreads; they are where they need to be. */
+ if (kthread_is_per_cpu(p))
+ return 0;
+
+ if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
+ int cpu;
+
+ schedstat_inc(p->stats.nr_failed_migrations_affine);
+
+ env->flags |= LBF_SOME_PINNED;
+
+ /*
+ * Remember if this task can be migrated to any other CPU in
+ * our sched_group. We may want to revisit it if we couldn't
+ * meet load balance goals by pulling other tasks on src_cpu.
+ *
+ * Avoid computing new_dst_cpu
+ * - for NEWLY_IDLE
+ * - if we have already computed one in current iteration
+ * - if it's an active balance
+ */
+ if (env->idle == CPU_NEWLY_IDLE ||
+ env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB))
+ return 0;
+
+ /* Prevent to re-select dst_cpu via env's CPUs: */
+ for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
+ if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
+ env->flags |= LBF_DST_PINNED;
+ env->new_dst_cpu = cpu;
+ break;
+ }
+ }
+
+ return 0;
+ }
+
+ /* Record that we found at least one task that could run on dst_cpu */
+ env->flags &= ~LBF_ALL_PINNED;
+
+ if (task_on_cpu(env->src_rq, p)) {
+ schedstat_inc(p->stats.nr_failed_migrations_running);
+ return 0;
+ }
+
+ /*
+ * Aggressive migration if:
+ * 1) active balance
+ * 2) destination numa is preferred
+ * 3) task is cache cold, or
+ * 4) too many balance attempts have failed.
+ */
+ if (env->flags & LBF_ACTIVE_LB)
+ return 1;
+
+ tsk_cache_hot = migrate_degrades_locality(p, env);
+ if (tsk_cache_hot == -1)
+ tsk_cache_hot = task_hot(p, env);
+
+ if (tsk_cache_hot <= 0 ||
+ env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
+ if (tsk_cache_hot == 1) {
+ schedstat_inc(env->sd->lb_hot_gained[env->idle]);
+ schedstat_inc(p->stats.nr_forced_migrations);
+ }
+ return 1;
+ }
+
+ schedstat_inc(p->stats.nr_failed_migrations_hot);
+ return 0;
+}
+
+/*
+ * detach_task() -- detach the task for the migration specified in env
+ */
+static void detach_task(struct task_struct *p, struct lb_env *env)
+{
+ lockdep_assert_rq_held(env->src_rq);
+
+ deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
+ set_task_cpu(p, env->dst_cpu);
+}
+
+/*
+ * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
+ * part of active balancing operations within "domain".
+ *
+ * Returns a task if successful and NULL otherwise.
+ */
+static struct task_struct *detach_one_task(struct lb_env *env)
+{
+ struct task_struct *p;
+
+ lockdep_assert_rq_held(env->src_rq);
+
+ list_for_each_entry_reverse(p,
+ &env->src_rq->cfs_tasks, se.group_node) {
+ if (!can_migrate_task(p, env))
+ continue;
+
+ detach_task(p, env);
+
+ /*
+ * Right now, this is only the second place where
+ * lb_gained[env->idle] is updated (other is detach_tasks)
+ * so we can safely collect stats here rather than
+ * inside detach_tasks().
+ */
+ schedstat_inc(env->sd->lb_gained[env->idle]);
+ return p;
+ }
+ return NULL;
+}
+
+/*
+ * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
+ * busiest_rq, as part of a balancing operation within domain "sd".
+ *
+ * Returns number of detached tasks if successful and 0 otherwise.
+ */
+static int detach_tasks(struct lb_env *env)
+{
+ struct list_head *tasks = &env->src_rq->cfs_tasks;
+ unsigned long util, load;
+ struct task_struct *p;
+ int detached = 0;
+
+ lockdep_assert_rq_held(env->src_rq);
+
+ /*
+ * Source run queue has been emptied by another CPU, clear
+ * LBF_ALL_PINNED flag as we will not test any task.
+ */
+ if (env->src_rq->nr_running <= 1) {
+ env->flags &= ~LBF_ALL_PINNED;
+ return 0;
+ }
+
+ if (env->imbalance <= 0)
+ return 0;
+
+ while (!list_empty(tasks)) {
+ /*
+ * We don't want to steal all, otherwise we may be treated likewise,
+ * which could at worst lead to a livelock crash.
+ */
+ if (env->idle && env->src_rq->nr_running <= 1)
+ break;
+
+ env->loop++;
+ /*
+ * We've more or less seen every task there is, call it quits
+ * unless we haven't found any movable task yet.
+ */
+ if (env->loop > env->loop_max &&
+ !(env->flags & LBF_ALL_PINNED))
+ break;
+
+ /* take a breather every nr_migrate tasks */
+ if (env->loop > env->loop_break) {
+ env->loop_break += SCHED_NR_MIGRATE_BREAK;
+ env->flags |= LBF_NEED_BREAK;
+ break;
+ }
+
+ p = list_last_entry(tasks, struct task_struct, se.group_node);
+
+ if (!can_migrate_task(p, env))
+ goto next;
+
+ switch (env->migration_type) {
+ case migrate_load:
+ /*
+ * Depending of the number of CPUs and tasks and the
+ * cgroup hierarchy, task_h_load() can return a null
+ * value. Make sure that env->imbalance decreases
+ * otherwise detach_tasks() will stop only after
+ * detaching up to loop_max tasks.
+ */
+ load = max_t(unsigned long, task_h_load(p), 1);
+
+ if (sched_feat(LB_MIN) &&
+ load < 16 && !env->sd->nr_balance_failed)
+ goto next;
+
+ /*
+ * Make sure that we don't migrate too much load.
+ * Nevertheless, let relax the constraint if
+ * scheduler fails to find a good waiting task to
+ * migrate.
+ */
+ if (shr_bound(load, env->sd->nr_balance_failed) > env->imbalance)
+ goto next;
+
+ env->imbalance -= load;
+ break;
+
+ case migrate_util:
+ util = task_util_est(p);
+
+ if (shr_bound(util, env->sd->nr_balance_failed) > env->imbalance)
+ goto next;
+
+ env->imbalance -= util;
+ break;
+
+ case migrate_task:
+ env->imbalance--;
+ break;
+
+ case migrate_misfit:
+ /* This is not a misfit task */
+ if (task_fits_cpu(p, env->src_cpu))
+ goto next;
+
+ env->imbalance = 0;
+ break;
+ }
+
+ detach_task(p, env);
+ list_add(&p->se.group_node, &env->tasks);
+
+ detached++;
+
+#ifdef CONFIG_PREEMPTION
+ /*
+ * NEWIDLE balancing is a source of latency, so preemptible
+ * kernels will stop after the first task is detached to minimize
+ * the critical section.
+ */
+ if (env->idle == CPU_NEWLY_IDLE)
+ break;
+#endif
+
+ /*
+ * We only want to steal up to the prescribed amount of
+ * load/util/tasks.
+ */
+ if (env->imbalance <= 0)
+ break;
+
+ continue;
+next:
+ list_move(&p->se.group_node, tasks);
+ }
+
+ /*
+ * Right now, this is one of only two places we collect this stat
+ * so we can safely collect detach_one_task() stats here rather
+ * than inside detach_one_task().
+ */
+ schedstat_add(env->sd->lb_gained[env->idle], detached);
+
+ return detached;
+}
+
+/*
+ * attach_task() -- attach the task detached by detach_task() to its new rq.
+ */
+static void attach_task(struct rq *rq, struct task_struct *p)
+{
+ lockdep_assert_rq_held(rq);
+
+ WARN_ON_ONCE(task_rq(p) != rq);
+ activate_task(rq, p, ENQUEUE_NOCLOCK);
+ wakeup_preempt(rq, p, 0);
+}
+
+/*
+ * attach_one_task() -- attaches the task returned from detach_one_task() to
+ * its new rq.
+ */
+static void attach_one_task(struct rq *rq, struct task_struct *p)
+{
+ struct rq_flags rf;
+
+ rq_lock(rq, &rf);
+ update_rq_clock(rq);
+ attach_task(rq, p);
+ rq_unlock(rq, &rf);
+}
+
+/*
+ * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
+ * new rq.
+ */
+static void attach_tasks(struct lb_env *env)
+{
+ struct list_head *tasks = &env->tasks;
+ struct task_struct *p;
+ struct rq_flags rf;
+
+ rq_lock(env->dst_rq, &rf);
+ update_rq_clock(env->dst_rq);
+
+ while (!list_empty(tasks)) {
+ p = list_first_entry(tasks, struct task_struct, se.group_node);
+ list_del_init(&p->se.group_node);
+
+ attach_task(env->dst_rq, p);
+ }
+
+ rq_unlock(env->dst_rq, &rf);
+}
+
+#ifdef CONFIG_NO_HZ_COMMON
+static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
+{
+ if (cfs_rq->avg.load_avg)
+ return true;
+
+ if (cfs_rq->avg.util_avg)
+ return true;
+
+ return false;
+}
+
+static inline bool others_have_blocked(struct rq *rq)
+{
+ if (cpu_util_rt(rq))
+ return true;
+
+ if (cpu_util_dl(rq))
+ return true;
+
+ if (thermal_load_avg(rq))
+ return true;
+
+ if (cpu_util_irq(rq))
+ return true;
+
+ return false;
+}
+
+static inline void update_blocked_load_tick(struct rq *rq)
+{
+ WRITE_ONCE(rq->last_blocked_load_update_tick, jiffies);
+}
+
+static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
+{
+ if (!has_blocked)
+ rq->has_blocked_load = 0;
+}
+#else
+static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; }
+static inline bool others_have_blocked(struct rq *rq) { return false; }
+static inline void update_blocked_load_tick(struct rq *rq) {}
+static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {}
+#endif
+
+static bool __update_blocked_others(struct rq *rq, bool *done)
+{
+ const struct sched_class *curr_class;
+ u64 now = rq_clock_pelt(rq);
+ unsigned long thermal_pressure;
+ bool decayed;
+
+ /*
+ * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
+ * DL and IRQ signals have been updated before updating CFS.
+ */
+ curr_class = rq->curr->sched_class;
+
+ thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
+
+ decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
+ update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
+ update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
+ update_irq_load_avg(rq, 0);
+
+ if (others_have_blocked(rq))
+ *done = false;
+
+ return decayed;
+}
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+
+static bool __update_blocked_fair(struct rq *rq, bool *done)
+{
+ struct cfs_rq *cfs_rq, *pos;
+ bool decayed = false;
+ int cpu = cpu_of(rq);
+
+ /*
+ * Iterates the task_group tree in a bottom up fashion, see
+ * list_add_leaf_cfs_rq() for details.
+ */
+ for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
+ struct sched_entity *se;
+
+ if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
+ update_tg_load_avg(cfs_rq);
+
+ if (cfs_rq->nr_running == 0)
+ update_idle_cfs_rq_clock_pelt(cfs_rq);
+
+ if (cfs_rq == &rq->cfs)
+ decayed = true;
+ }
+
+ /* Propagate pending load changes to the parent, if any: */
+ se = cfs_rq->tg->se[cpu];
+ if (se && !skip_blocked_update(se))
+ update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
+
+ /*
+ * There can be a lot of idle CPU cgroups. Don't let fully
+ * decayed cfs_rqs linger on the list.
+ */
+ if (cfs_rq_is_decayed(cfs_rq))
+ list_del_leaf_cfs_rq(cfs_rq);
+
+ /* Don't need periodic decay once load/util_avg are null */
+ if (cfs_rq_has_blocked(cfs_rq))
+ *done = false;
+ }
+
+ return decayed;
+}
+
+/*
+ * Compute the hierarchical load factor for cfs_rq and all its ascendants.
+ * This needs to be done in a top-down fashion because the load of a child
+ * group is a fraction of its parents load.
+ */
+static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
+{
+ struct rq *rq = rq_of(cfs_rq);
+ struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
+ unsigned long now = jiffies;
+ unsigned long load;
+
+ if (cfs_rq->last_h_load_update == now)
+ return;
+
+ WRITE_ONCE(cfs_rq->h_load_next, NULL);
+ for_each_sched_entity(se) {
+ cfs_rq = cfs_rq_of(se);
+ WRITE_ONCE(cfs_rq->h_load_next, se);
+ if (cfs_rq->last_h_load_update == now)
+ break;
+ }
+
+ if (!se) {
+ cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
+ cfs_rq->last_h_load_update = now;
+ }
+
+ while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
+ load = cfs_rq->h_load;
+ load = div64_ul(load * se->avg.load_avg,
+ cfs_rq_load_avg(cfs_rq) + 1);
+ cfs_rq = group_cfs_rq(se);
+ cfs_rq->h_load = load;
+ cfs_rq->last_h_load_update = now;
+ }
+}
+
+unsigned long task_h_load(struct task_struct *p)
+{
+ struct cfs_rq *cfs_rq = task_cfs_rq(p);
+
+ update_cfs_rq_h_load(cfs_rq);
+ return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
+ cfs_rq_load_avg(cfs_rq) + 1);
+}
+#else
+static bool __update_blocked_fair(struct rq *rq, bool *done)
+{
+ struct cfs_rq *cfs_rq = &rq->cfs;
+ bool decayed;
+
+ decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
+ if (cfs_rq_has_blocked(cfs_rq))
+ *done = false;
+
+ return decayed;
+}
+
+#endif
+
+
+static void sched_balance_update_blocked_averages(int cpu)
+{
+ bool decayed = false, done = true;
+ struct rq *rq = cpu_rq(cpu);
+ struct rq_flags rf;
+
+ rq_lock_irqsave(rq, &rf);
+ update_blocked_load_tick(rq);
+ update_rq_clock(rq);
+
+ decayed |= __update_blocked_others(rq, &done);
+ decayed |= __update_blocked_fair(rq, &done);
+
+ update_blocked_load_status(rq, !done);
+ if (decayed)
+ cpufreq_update_util(rq, 0);
+ rq_unlock_irqrestore(rq, &rf);
+}
+
+/********** Helpers for sched_balance_find_src_group ************************/
+
+/*
+ * sg_lb_stats - stats of a sched_group required for load-balancing:
+ */
+struct sg_lb_stats {
+ unsigned long avg_load; /* Avg load over the CPUs of the group */
+ unsigned long group_load; /* Total load over the CPUs of the group */
+ unsigned long group_capacity; /* Capacity over the CPUs of the group */
+ unsigned long group_util; /* Total utilization over the CPUs of the group */
+ unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
+ unsigned int sum_nr_running; /* Nr of all tasks running in the group */
+ unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
+ unsigned int idle_cpus; /* Nr of idle CPUs in the group */
+ unsigned int group_weight;
+ enum group_type group_type;
+ unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
+ unsigned int group_smt_balance; /* Task on busy SMT be moved */
+ unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
+#ifdef CONFIG_NUMA_BALANCING
+ unsigned int nr_numa_running;
+ unsigned int nr_preferred_running;
+#endif
+};
+
+/*
+ * sd_lb_stats - stats of a sched_domain required for load-balancing:
+ */
+struct sd_lb_stats {
+ struct sched_group *busiest; /* Busiest group in this sd */
+ struct sched_group *local; /* Local group in this sd */
+ unsigned long total_load; /* Total load of all groups in sd */
+ unsigned long total_capacity; /* Total capacity of all groups in sd */
+ unsigned long avg_load; /* Average load across all groups in sd */
+ unsigned int prefer_sibling; /* Tasks should go to sibling first */
+
+ struct sg_lb_stats busiest_stat; /* Statistics of the busiest group */
+ struct sg_lb_stats local_stat; /* Statistics of the local group */
+};
+
+static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
+{
+ /*
+ * Skimp on the clearing to avoid duplicate work. We can avoid clearing
+ * local_stat because update_sg_lb_stats() does a full clear/assignment.
+ * We must however set busiest_stat::group_type and
+ * busiest_stat::idle_cpus to the worst busiest group because
+ * update_sd_pick_busiest() reads these before assignment.
+ */
+ *sds = (struct sd_lb_stats){
+ .busiest = NULL,
+ .local = NULL,
+ .total_load = 0UL,
+ .total_capacity = 0UL,
+ .busiest_stat = {
+ .idle_cpus = UINT_MAX,
+ .group_type = group_has_spare,
+ },
+ };
+}
+
+static unsigned long scale_rt_capacity(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ unsigned long max = arch_scale_cpu_capacity(cpu);
+ unsigned long used, free;
+ unsigned long irq;
+
+ irq = cpu_util_irq(rq);
+
+ if (unlikely(irq >= max))
+ return 1;
+
+ /*
+ * avg_rt.util_avg and avg_dl.util_avg track binary signals
+ * (running and not running) with weights 0 and 1024 respectively.
+ * avg_thermal.load_avg tracks thermal pressure and the weighted
+ * average uses the actual delta max capacity(load).
+ */
+ used = cpu_util_rt(rq);
+ used += cpu_util_dl(rq);
+ used += thermal_load_avg(rq);
+
+ if (unlikely(used >= max))
+ return 1;
+
+ free = max - used;
+
+ return scale_irq_capacity(free, irq, max);
+}
+
+static void update_cpu_capacity(struct sched_domain *sd, int cpu)
+{
+ unsigned long capacity = scale_rt_capacity(cpu);
+ struct sched_group *sdg = sd->groups;
+
+ if (!capacity)
+ capacity = 1;
+
+ cpu_rq(cpu)->cpu_capacity = capacity;
+ trace_sched_cpu_capacity_tp(cpu_rq(cpu));
+
+ sdg->sgc->capacity = capacity;
+ sdg->sgc->min_capacity = capacity;
+ sdg->sgc->max_capacity = capacity;
+}
+
+void update_group_capacity(struct sched_domain *sd, int cpu)
+{
+ struct sched_domain *child = sd->child;
+ struct sched_group *group, *sdg = sd->groups;
+ unsigned long capacity, min_capacity, max_capacity;
+ unsigned long interval;
+
+ interval = msecs_to_jiffies(sd->balance_interval);
+ interval = clamp(interval, 1UL, max_load_balance_interval);
+ sdg->sgc->next_update = jiffies + interval;
+
+ if (!child) {
+ update_cpu_capacity(sd, cpu);
+ return;
+ }
+
+ capacity = 0;
+ min_capacity = ULONG_MAX;
+ max_capacity = 0;
+
+ if (child->flags & SD_OVERLAP) {
+ /*
+ * SD_OVERLAP domains cannot assume that child groups
+ * span the current group.
+ */
+
+ for_each_cpu(cpu, sched_group_span(sdg)) {
+ unsigned long cpu_cap = capacity_of(cpu);
+
+ capacity += cpu_cap;
+ min_capacity = min(cpu_cap, min_capacity);
+ max_capacity = max(cpu_cap, max_capacity);
+ }
+ } else {
+ /*
+ * !SD_OVERLAP domains can assume that child groups
+ * span the current group.
+ */
+
+ group = child->groups;
+ do {
+ struct sched_group_capacity *sgc = group->sgc;
+
+ capacity += sgc->capacity;
+ min_capacity = min(sgc->min_capacity, min_capacity);
+ max_capacity = max(sgc->max_capacity, max_capacity);
+ group = group->next;
+ } while (group != child->groups);
+ }
+
+ sdg->sgc->capacity = capacity;
+ sdg->sgc->min_capacity = min_capacity;
+ sdg->sgc->max_capacity = max_capacity;
+}
+
+/*
+ * Check whether the capacity of the rq has been noticeably reduced by side
+ * activity. The imbalance_pct is used for the threshold.
+ * Return true is the capacity is reduced
+ */
+static inline int
+check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
+{
+ return ((rq->cpu_capacity * sd->imbalance_pct) <
+ (arch_scale_cpu_capacity(cpu_of(rq)) * 100));
+}
+
+/* Check if the rq has a misfit task */
+static inline bool check_misfit_status(struct rq *rq)
+{
+ return rq->misfit_task_load;
+}
+
+/*
+ * Group imbalance indicates (and tries to solve) the problem where balancing
+ * groups is inadequate due to ->cpus_ptr constraints.
+ *
+ * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
+ * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
+ * Something like:
+ *
+ * { 0 1 2 3 } { 4 5 6 7 }
+ * * * * *
+ *
+ * If we were to balance group-wise we'd place two tasks in the first group and
+ * two tasks in the second group. Clearly this is undesired as it will overload
+ * cpu 3 and leave one of the CPUs in the second group unused.
+ *
+ * The current solution to this issue is detecting the skew in the first group
+ * by noticing the lower domain failed to reach balance and had difficulty
+ * moving tasks due to affinity constraints.
+ *
+ * When this is so detected; this group becomes a candidate for busiest; see
+ * update_sd_pick_busiest(). And calculate_imbalance() and
+ * sched_balance_find_src_group() avoid some of the usual balance conditions to allow it
+ * to create an effective group imbalance.
+ *
+ * This is a somewhat tricky proposition since the next run might not find the
+ * group imbalance and decide the groups need to be balanced again. A most
+ * subtle and fragile situation.
+ */
+
+static inline int sg_imbalanced(struct sched_group *group)
+{
+ return group->sgc->imbalance;
+}
+
+/*
+ * group_has_capacity returns true if the group has spare capacity that could
+ * be used by some tasks.
+ * We consider that a group has spare capacity if the number of task is
+ * smaller than the number of CPUs or if the utilization is lower than the
+ * available capacity for CFS tasks.
+ * For the latter, we use a threshold to stabilize the state, to take into
+ * account the variance of the tasks' load and to return true if the available
+ * capacity in meaningful for the load balancer.
+ * As an example, an available capacity of 1% can appear but it doesn't make
+ * any benefit for the load balance.
+ */
+static inline bool
+group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
+{
+ if (sgs->sum_nr_running < sgs->group_weight)
+ return true;
+
+ if ((sgs->group_capacity * imbalance_pct) <
+ (sgs->group_runnable * 100))
+ return false;
+
+ if ((sgs->group_capacity * 100) >
+ (sgs->group_util * imbalance_pct))
+ return true;
+
+ return false;
+}
+
+/*
+ * group_is_overloaded returns true if the group has more tasks than it can
+ * handle.
+ * group_is_overloaded is not equals to !group_has_capacity because a group
+ * with the exact right number of tasks, has no more spare capacity but is not
+ * overloaded so both group_has_capacity and group_is_overloaded return
+ * false.
+ */
+static inline bool
+group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
+{
+ if (sgs->sum_nr_running <= sgs->group_weight)
+ return false;
+
+ if ((sgs->group_capacity * 100) <
+ (sgs->group_util * imbalance_pct))
+ return true;
+
+ if ((sgs->group_capacity * imbalance_pct) <
+ (sgs->group_runnable * 100))
+ return true;
+
+ return false;
+}
+
+static inline enum
+group_type group_classify(unsigned int imbalance_pct,
+ struct sched_group *group,
+ struct sg_lb_stats *sgs)
+{
+ if (group_is_overloaded(imbalance_pct, sgs))
+ return group_overloaded;
+
+ if (sg_imbalanced(group))
+ return group_imbalanced;
+
+ if (sgs->group_asym_packing)
+ return group_asym_packing;
+
+ if (sgs->group_smt_balance)
+ return group_smt_balance;
+
+ if (sgs->group_misfit_task_load)
+ return group_misfit_task;
+
+ if (!group_has_capacity(imbalance_pct, sgs))
+ return group_fully_busy;
+
+ return group_has_spare;
+}
+
+/**
+ * sched_use_asym_prio - Check whether asym_packing priority must be used
+ * @sd: The scheduling domain of the load balancing
+ * @cpu: A CPU
+ *
+ * Always use CPU priority when balancing load between SMT siblings. When
+ * balancing load between cores, it is not sufficient that @cpu is idle. Only
+ * use CPU priority if the whole core is idle.
+ *
+ * Returns: True if the priority of @cpu must be followed. False otherwise.
+ */
+static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
+{
+ if (!(sd->flags & SD_ASYM_PACKING))
+ return false;
+
+ if (!sched_smt_active())
+ return true;
+
+ return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu);
+}
+
+static inline bool sched_asym(struct sched_domain *sd, int dst_cpu, int src_cpu)
+{
+ /*
+ * First check if @dst_cpu can do asym_packing load balance. Only do it
+ * if it has higher priority than @src_cpu.
+ */
+ return sched_use_asym_prio(sd, dst_cpu) &&
+ sched_asym_prefer(dst_cpu, src_cpu);
+}
+
+/**
+ * sched_group_asym - Check if the destination CPU can do asym_packing balance
+ * @env: The load balancing environment
+ * @sgs: Load-balancing statistics of the candidate busiest group
+ * @group: The candidate busiest group
+ *
+ * @env::dst_cpu can do asym_packing if it has higher priority than the
+ * preferred CPU of @group.
+ *
+ * Return: true if @env::dst_cpu can do with asym_packing load balance. False
+ * otherwise.
+ */
+static inline bool
+sched_group_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
+{
+ /*
+ * CPU priorities do not make sense for SMT cores with more than one
+ * busy sibling.
+ */
+ if ((group->flags & SD_SHARE_CPUCAPACITY) &&
+ (sgs->group_weight - sgs->idle_cpus != 1))
+ return false;
+
+ return sched_asym(env->sd, env->dst_cpu, group->asym_prefer_cpu);
+}
+
+/* One group has more than one SMT CPU while the other group does not */
+static inline bool smt_vs_nonsmt_groups(struct sched_group *sg1,
+ struct sched_group *sg2)
+{
+ if (!sg1 || !sg2)
+ return false;
+
+ return (sg1->flags & SD_SHARE_CPUCAPACITY) !=
+ (sg2->flags & SD_SHARE_CPUCAPACITY);
+}
+
+static inline bool smt_balance(struct lb_env *env, struct sg_lb_stats *sgs,
+ struct sched_group *group)
+{
+ if (!env->idle)
+ return false;
+
+ /*
+ * For SMT source group, it is better to move a task
+ * to a CPU that doesn't have multiple tasks sharing its CPU capacity.
+ * Note that if a group has a single SMT, SD_SHARE_CPUCAPACITY
+ * will not be on.
+ */
+ if (group->flags & SD_SHARE_CPUCAPACITY &&
+ sgs->sum_h_nr_running > 1)
+ return true;
+
+ return false;
+}
+
+static inline long sibling_imbalance(struct lb_env *env,
+ struct sd_lb_stats *sds,
+ struct sg_lb_stats *busiest,
+ struct sg_lb_stats *local)
+{
+ int ncores_busiest, ncores_local;
+ long imbalance;
+
+ if (!env->idle || !busiest->sum_nr_running)
+ return 0;
+
+ ncores_busiest = sds->busiest->cores;
+ ncores_local = sds->local->cores;
+
+ if (ncores_busiest == ncores_local) {
+ imbalance = busiest->sum_nr_running;
+ lsub_positive(&imbalance, local->sum_nr_running);
+ return imbalance;
+ }
+
+ /* Balance such that nr_running/ncores ratio are same on both groups */
+ imbalance = ncores_local * busiest->sum_nr_running;
+ lsub_positive(&imbalance, ncores_busiest * local->sum_nr_running);
+ /* Normalize imbalance and do rounding on normalization */
+ imbalance = 2 * imbalance + ncores_local + ncores_busiest;
+ imbalance /= ncores_local + ncores_busiest;
+
+ /* Take advantage of resource in an empty sched group */
+ if (imbalance <= 1 && local->sum_nr_running == 0 &&
+ busiest->sum_nr_running > 1)
+ imbalance = 2;
+
+ return imbalance;
+}
+
+static inline bool
+sched_reduced_capacity(struct rq *rq, struct sched_domain *sd)
+{
+ /*
+ * When there is more than 1 task, the group_overloaded case already
+ * takes care of cpu with reduced capacity
+ */
+ if (rq->cfs.h_nr_running != 1)
+ return false;
+
+ return check_cpu_capacity(rq, sd);
+}
+
+/**
+ * update_sg_lb_stats - Update sched_group's statistics for load balancing.
+ * @env: The load balancing environment.
+ * @sds: Load-balancing data with statistics of the local group.
+ * @group: sched_group whose statistics are to be updated.
+ * @sgs: variable to hold the statistics for this group.
+ * @sg_overloaded: sched_group is overloaded
+ * @sg_overutilized: sched_group is overutilized
+ */
+static inline void update_sg_lb_stats(struct lb_env *env,
+ struct sd_lb_stats *sds,
+ struct sched_group *group,
+ struct sg_lb_stats *sgs,
+ bool *sg_overloaded,
+ bool *sg_overutilized)
+{
+ int i, nr_running, local_group;
+
+ memset(sgs, 0, sizeof(*sgs));
+
+ local_group = group == sds->local;
+
+ for_each_cpu_and(i, sched_group_span(group), env->cpus) {
+ struct rq *rq = cpu_rq(i);
+ unsigned long load = cpu_load(rq);
+
+ sgs->group_load += load;
+ sgs->group_util += cpu_util_cfs(i);
+ sgs->group_runnable += cpu_runnable(rq);
+ sgs->sum_h_nr_running += rq->cfs.h_nr_running;
+
+ nr_running = rq->nr_running;
+ sgs->sum_nr_running += nr_running;
+
+ if (nr_running > 1)
+ *sg_overloaded = 1;
+
+ if (cpu_overutilized(i))
+ *sg_overutilized = 1;
+
+#ifdef CONFIG_NUMA_BALANCING
+ sgs->nr_numa_running += rq->nr_numa_running;
+ sgs->nr_preferred_running += rq->nr_preferred_running;
+#endif
+ /*
+ * No need to call idle_cpu() if nr_running is not 0
+ */
+ if (!nr_running && idle_cpu(i)) {
+ sgs->idle_cpus++;
+ /* Idle cpu can't have misfit task */
+ continue;
+ }
+
+ if (local_group)
+ continue;
+
+ if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
+ /* Check for a misfit task on the cpu */
+ if (sgs->group_misfit_task_load < rq->misfit_task_load) {
+ sgs->group_misfit_task_load = rq->misfit_task_load;
+ *sg_overloaded = 1;
+ }
+ } else if (env->idle && sched_reduced_capacity(rq, env->sd)) {
+ /* Check for a task running on a CPU with reduced capacity */
+ if (sgs->group_misfit_task_load < load)
+ sgs->group_misfit_task_load = load;
+ }
+ }
+
+ sgs->group_capacity = group->sgc->capacity;
+
+ sgs->group_weight = group->group_weight;
+
+ /* Check if dst CPU is idle and preferred to this group */
+ if (!local_group && env->idle && sgs->sum_h_nr_running &&
+ sched_group_asym(env, sgs, group))
+ sgs->group_asym_packing = 1;
+
+ /* Check for loaded SMT group to be balanced to dst CPU */
+ if (!local_group && smt_balance(env, sgs, group))
+ sgs->group_smt_balance = 1;
+
+ sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
+
+ /* Computing avg_load makes sense only when group is overloaded */
+ if (sgs->group_type == group_overloaded)
+ sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
+ sgs->group_capacity;
+}
+
+/**
+ * update_sd_pick_busiest - return 1 on busiest group
+ * @env: The load balancing environment.
+ * @sds: sched_domain statistics
+ * @sg: sched_group candidate to be checked for being the busiest
+ * @sgs: sched_group statistics
+ *
+ * Determine if @sg is a busier group than the previously selected
+ * busiest group.
+ *
+ * Return: %true if @sg is a busier group than the previously selected
+ * busiest group. %false otherwise.
+ */
+static bool update_sd_pick_busiest(struct lb_env *env,
+ struct sd_lb_stats *sds,
+ struct sched_group *sg,
+ struct sg_lb_stats *sgs)
+{
+ struct sg_lb_stats *busiest = &sds->busiest_stat;
+
+ /* Make sure that there is at least one task to pull */
+ if (!sgs->sum_h_nr_running)
+ return false;
+
+ /*
+ * Don't try to pull misfit tasks we can't help.
+ * We can use max_capacity here as reduction in capacity on some
+ * CPUs in the group should either be possible to resolve
+ * internally or be covered by avg_load imbalance (eventually).
+ */
+ if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
+ (sgs->group_type == group_misfit_task) &&
+ (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
+ sds->local_stat.group_type != group_has_spare))
+ return false;
+
+ if (sgs->group_type > busiest->group_type)
+ return true;
+
+ if (sgs->group_type < busiest->group_type)
+ return false;
+
+ /*
+ * The candidate and the current busiest group are the same type of
+ * group. Let check which one is the busiest according to the type.
+ */
+
+ switch (sgs->group_type) {
+ case group_overloaded:
+ /* Select the overloaded group with highest avg_load. */
+ return sgs->avg_load > busiest->avg_load;
+
+ case group_imbalanced:
+ /*
+ * Select the 1st imbalanced group as we don't have any way to
+ * choose one more than another.
+ */
+ return false;
+
+ case group_asym_packing:
+ /* Prefer to move from lowest priority CPU's work */
+ return sched_asym_prefer(sds->busiest->asym_prefer_cpu, sg->asym_prefer_cpu);
+
+ case group_misfit_task:
+ /*
+ * If we have more than one misfit sg go with the biggest
+ * misfit.
+ */
+ return sgs->group_misfit_task_load > busiest->group_misfit_task_load;
+
+ case group_smt_balance:
+ /*
+ * Check if we have spare CPUs on either SMT group to
+ * choose has spare or fully busy handling.
+ */
+ if (sgs->idle_cpus != 0 || busiest->idle_cpus != 0)
+ goto has_spare;
+
+ fallthrough;
+
+ case group_fully_busy:
+ /*
+ * Select the fully busy group with highest avg_load. In
+ * theory, there is no need to pull task from such kind of
+ * group because tasks have all compute capacity that they need
+ * but we can still improve the overall throughput by reducing
+ * contention when accessing shared HW resources.
+ *
+ * XXX for now avg_load is not computed and always 0 so we
+ * select the 1st one, except if @sg is composed of SMT
+ * siblings.
+ */
+
+ if (sgs->avg_load < busiest->avg_load)
+ return false;
+
+ if (sgs->avg_load == busiest->avg_load) {
+ /*
+ * SMT sched groups need more help than non-SMT groups.
+ * If @sg happens to also be SMT, either choice is good.
+ */
+ if (sds->busiest->flags & SD_SHARE_CPUCAPACITY)
+ return false;
+ }
+
+ break;
+
+ case group_has_spare:
+ /*
+ * Do not pick sg with SMT CPUs over sg with pure CPUs,
+ * as we do not want to pull task off SMT core with one task
+ * and make the core idle.
+ */
+ if (smt_vs_nonsmt_groups(sds->busiest, sg)) {
+ if (sg->flags & SD_SHARE_CPUCAPACITY && sgs->sum_h_nr_running <= 1)
+ return false;
+ else
+ return true;
+ }
+has_spare:
+
+ /*
+ * Select not overloaded group with lowest number of idle CPUs
+ * and highest number of running tasks. We could also compare
+ * the spare capacity which is more stable but it can end up
+ * that the group has less spare capacity but finally more idle
+ * CPUs which means less opportunity to pull tasks.
+ */
+ if (sgs->idle_cpus > busiest->idle_cpus)
+ return false;
+ else if ((sgs->idle_cpus == busiest->idle_cpus) &&
+ (sgs->sum_nr_running <= busiest->sum_nr_running))
+ return false;
+
+ break;
+ }
+
+ /*
+ * Candidate sg has no more than one task per CPU and has higher
+ * per-CPU capacity. Migrating tasks to less capable CPUs may harm
+ * throughput. Maximize throughput, power/energy consequences are not
+ * considered.
+ */
+ if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
+ (sgs->group_type <= group_fully_busy) &&
+ (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
+ return false;
+
+ return true;
+}
+
+#ifdef CONFIG_NUMA_BALANCING
+static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
+{
+ if (sgs->sum_h_nr_running > sgs->nr_numa_running)
+ return regular;
+ if (sgs->sum_h_nr_running > sgs->nr_preferred_running)
+ return remote;
+ return all;
+}
+
+static inline enum fbq_type fbq_classify_rq(struct rq *rq)
+{
+ if (rq->nr_running > rq->nr_numa_running)
+ return regular;
+ if (rq->nr_running > rq->nr_preferred_running)
+ return remote;
+ return all;
+}
+#else
+static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
+{
+ return all;
+}
+
+static inline enum fbq_type fbq_classify_rq(struct rq *rq)
+{
+ return regular;
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
+
+struct sg_lb_stats;
+
+/*
+ * task_running_on_cpu - return 1 if @p is running on @cpu.
+ */
+
+static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
+{
+ /* Task has no contribution or is new */
+ if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
+ return 0;
+
+ if (task_on_rq_queued(p))
+ return 1;
+
+ return 0;
+}
+
+/**
+ * idle_cpu_without - would a given CPU be idle without p ?
+ * @cpu: the processor on which idleness is tested.
+ * @p: task which should be ignored.
+ *
+ * Return: 1 if the CPU would be idle. 0 otherwise.
+ */
+static int idle_cpu_without(int cpu, struct task_struct *p)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ if (rq->curr != rq->idle && rq->curr != p)
+ return 0;
+
+ /*
+ * rq->nr_running can't be used but an updated version without the
+ * impact of p on cpu must be used instead. The updated nr_running
+ * be computed and tested before calling idle_cpu_without().
+ */
+
+ if (rq->ttwu_pending)
+ return 0;
+
+ return 1;
+}
+
+/*
+ * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
+ * @sd: The sched_domain level to look for idlest group.
+ * @group: sched_group whose statistics are to be updated.
+ * @sgs: variable to hold the statistics for this group.
+ * @p: The task for which we look for the idlest group/CPU.
+ */
+static inline void update_sg_wakeup_stats(struct sched_domain *sd,
+ struct sched_group *group,
+ struct sg_lb_stats *sgs,
+ struct task_struct *p)
+{
+ int i, nr_running;
+
+ memset(sgs, 0, sizeof(*sgs));
+
+ /* Assume that task can't fit any CPU of the group */
+ if (sd->flags & SD_ASYM_CPUCAPACITY)
+ sgs->group_misfit_task_load = 1;
+
+ for_each_cpu(i, sched_group_span(group)) {
+ struct rq *rq = cpu_rq(i);
+ unsigned int local;
+
+ sgs->group_load += cpu_load_without(rq, p);
+ sgs->group_util += cpu_util_without(i, p);
+ sgs->group_runnable += cpu_runnable_without(rq, p);
+ local = task_running_on_cpu(i, p);
+ sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;
+
+ nr_running = rq->nr_running - local;
+ sgs->sum_nr_running += nr_running;
+
+ /*
+ * No need to call idle_cpu_without() if nr_running is not 0
+ */
+ if (!nr_running && idle_cpu_without(i, p))
+ sgs->idle_cpus++;
+
+ /* Check if task fits in the CPU */
+ if (sd->flags & SD_ASYM_CPUCAPACITY &&
+ sgs->group_misfit_task_load &&
+ task_fits_cpu(p, i))
+ sgs->group_misfit_task_load = 0;
+
+ }
+
+ sgs->group_capacity = group->sgc->capacity;
+
+ sgs->group_weight = group->group_weight;
+
+ sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
+
+ /*
+ * Computing avg_load makes sense only when group is fully busy or
+ * overloaded
+ */
+ if (sgs->group_type == group_fully_busy ||
+ sgs->group_type == group_overloaded)
+ sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
+ sgs->group_capacity;
+}
+
+static bool update_pick_idlest(struct sched_group *idlest,
+ struct sg_lb_stats *idlest_sgs,
+ struct sched_group *group,
+ struct sg_lb_stats *sgs)
+{
+ if (sgs->group_type < idlest_sgs->group_type)
+ return true;
+
+ if (sgs->group_type > idlest_sgs->group_type)
+ return false;
+
+ /*
+ * The candidate and the current idlest group are the same type of
+ * group. Let check which one is the idlest according to the type.
+ */
+
+ switch (sgs->group_type) {
+ case group_overloaded:
+ case group_fully_busy:
+ /* Select the group with lowest avg_load. */
+ if (idlest_sgs->avg_load <= sgs->avg_load)
+ return false;
+ break;
+
+ case group_imbalanced:
+ case group_asym_packing:
+ case group_smt_balance:
+ /* Those types are not used in the slow wakeup path */
+ return false;
+
+ case group_misfit_task:
+ /* Select group with the highest max capacity */
+ if (idlest->sgc->max_capacity >= group->sgc->max_capacity)
+ return false;
+ break;
+
+ case group_has_spare:
+ /* Select group with most idle CPUs */
+ if (idlest_sgs->idle_cpus > sgs->idle_cpus)
+ return false;
+
+ /* Select group with lowest group_util */
+ if (idlest_sgs->idle_cpus == sgs->idle_cpus &&
+ idlest_sgs->group_util <= sgs->group_util)
+ return false;
+
+ break;
+ }
+
+ return true;
+}
+
+/*
+ * sched_balance_find_dst_group() finds and returns the least busy CPU group within the
+ * domain.
+ *
+ * Assumes p is allowed on at least one CPU in sd.
+ */
+struct sched_group *
+sched_balance_find_dst_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
+{
+ struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
+ struct sg_lb_stats local_sgs, tmp_sgs;
+ struct sg_lb_stats *sgs;
+ unsigned long imbalance;
+ struct sg_lb_stats idlest_sgs = {
+ .avg_load = UINT_MAX,
+ .group_type = group_overloaded,
+ };
+
+ do {
+ int local_group;
+
+ /* Skip over this group if it has no CPUs allowed */
+ if (!cpumask_intersects(sched_group_span(group),
+ p->cpus_ptr))
+ continue;
+
+ /* Skip over this group if no cookie matched */
+ if (!sched_group_cookie_match(cpu_rq(this_cpu), p, group))
+ continue;
+
+ local_group = cpumask_test_cpu(this_cpu,
+ sched_group_span(group));
+
+ if (local_group) {
+ sgs = &local_sgs;
+ local = group;
+ } else {
+ sgs = &tmp_sgs;
+ }
+
+ update_sg_wakeup_stats(sd, group, sgs, p);
+
+ if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
+ idlest = group;
+ idlest_sgs = *sgs;
+ }
+
+ } while (group = group->next, group != sd->groups);
+
+
+ /* There is no idlest group to push tasks to */
+ if (!idlest)
+ return NULL;
+
+ /* The local group has been skipped because of CPU affinity */
+ if (!local)
+ return idlest;
+
+ /*
+ * If the local group is idler than the selected idlest group
+ * don't try and push the task.
+ */
+ if (local_sgs.group_type < idlest_sgs.group_type)
+ return NULL;
+
+ /*
+ * If the local group is busier than the selected idlest group
+ * try and push the task.
+ */
+ if (local_sgs.group_type > idlest_sgs.group_type)
+ return idlest;
+
+ switch (local_sgs.group_type) {
+ case group_overloaded:
+ case group_fully_busy:
+
+ /* Calculate allowed imbalance based on load */
+ imbalance = scale_load_down(NICE_0_LOAD) *
+ (sd->imbalance_pct-100) / 100;
+
+ /*
+ * When comparing groups across NUMA domains, it's possible for
+ * the local domain to be very lightly loaded relative to the
+ * remote domains but "imbalance" skews the comparison making
+ * remote CPUs look much more favourable. When considering
+ * cross-domain, add imbalance to the load on the remote node
+ * and consider staying local.
+ */
+
+ if ((sd->flags & SD_NUMA) &&
+ ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load))
+ return NULL;
+
+ /*
+ * If the local group is less loaded than the selected
+ * idlest group don't try and push any tasks.
+ */
+ if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance))
+ return NULL;
+
+ if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load)
+ return NULL;
+ break;
+
+ case group_imbalanced:
+ case group_asym_packing:
+ case group_smt_balance:
+ /* Those type are not used in the slow wakeup path */
+ return NULL;
+
+ case group_misfit_task:
+ /* Select group with the highest max capacity */
+ if (local->sgc->max_capacity >= idlest->sgc->max_capacity)
+ return NULL;
+ break;
+
+ case group_has_spare:
+#ifdef CONFIG_NUMA
+ if (sd->flags & SD_NUMA) {
+ int imb_numa_nr = sd->imb_numa_nr;
+#ifdef CONFIG_NUMA_BALANCING
+ int idlest_cpu;
+ /*
+ * If there is spare capacity at NUMA, try to select
+ * the preferred node
+ */
+ if (cpu_to_node(this_cpu) == p->numa_preferred_nid)
+ return NULL;
+
+ idlest_cpu = cpumask_first(sched_group_span(idlest));
+ if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid)
+ return idlest;
+#endif /* CONFIG_NUMA_BALANCING */
+ /*
+ * Otherwise, keep the task close to the wakeup source
+ * and improve locality if the number of running tasks
+ * would remain below threshold where an imbalance is
+ * allowed while accounting for the possibility the
+ * task is pinned to a subset of CPUs. If there is a
+ * real need of migration, periodic load balance will
+ * take care of it.
+ */
+ if (p->nr_cpus_allowed != NR_CPUS) {
+ struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
+
+ cpumask_and(cpus, sched_group_span(local), p->cpus_ptr);
+ imb_numa_nr = min(cpumask_weight(cpus), sd->imb_numa_nr);
+ }
+
+ imbalance = abs(local_sgs.idle_cpus - idlest_sgs.idle_cpus);
+ if (!adjust_numa_imbalance(imbalance,
+ local_sgs.sum_nr_running + 1,
+ imb_numa_nr)) {
+ return NULL;
+ }
+ }
+#endif /* CONFIG_NUMA */
+
+ /*
+ * Select group with highest number of idle CPUs. We could also
+ * compare the utilization which is more stable but it can end
+ * up that the group has less spare capacity but finally more
+ * idle CPUs which means more opportunity to run task.
+ */
+ if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus)
+ return NULL;
+ break;
+ }
+
+ return idlest;
+}
+
+static void update_idle_cpu_scan(struct lb_env *env,
+ unsigned long sum_util)
+{
+ struct sched_domain_shared *sd_share;
+ int llc_weight, pct;
+ u64 x, y, tmp;
+ /*
+ * Update the number of CPUs to scan in LLC domain, which could
+ * be used as a hint in select_idle_cpu(). The update of sd_share
+ * could be expensive because it is within a shared cache line.
+ * So the write of this hint only occurs during periodic load
+ * balancing, rather than CPU_NEWLY_IDLE, because the latter
+ * can fire way more frequently than the former.
+ */
+ if (!sched_feat(SIS_UTIL) || env->idle == CPU_NEWLY_IDLE)
+ return;
+
+ llc_weight = per_cpu(sd_llc_size, env->dst_cpu);
+ if (env->sd->span_weight != llc_weight)
+ return;
+
+ sd_share = rcu_dereference(per_cpu(sd_llc_shared, env->dst_cpu));
+ if (!sd_share)
+ return;
+
+ /*
+ * The number of CPUs to search drops as sum_util increases, when
+ * sum_util hits 85% or above, the scan stops.
+ * The reason to choose 85% as the threshold is because this is the
+ * imbalance_pct(117) when a LLC sched group is overloaded.
+ *
+ * let y = SCHED_CAPACITY_SCALE - p * x^2 [1]
+ * and y'= y / SCHED_CAPACITY_SCALE
+ *
+ * x is the ratio of sum_util compared to the CPU capacity:
+ * x = sum_util / (llc_weight * SCHED_CAPACITY_SCALE)
+ * y' is the ratio of CPUs to be scanned in the LLC domain,
+ * and the number of CPUs to scan is calculated by:
+ *
+ * nr_scan = llc_weight * y' [2]
+ *
+ * When x hits the threshold of overloaded, AKA, when
+ * x = 100 / pct, y drops to 0. According to [1],
+ * p should be SCHED_CAPACITY_SCALE * pct^2 / 10000
+ *
+ * Scale x by SCHED_CAPACITY_SCALE:
+ * x' = sum_util / llc_weight; [3]
+ *
+ * and finally [1] becomes:
+ * y = SCHED_CAPACITY_SCALE -
+ * x'^2 * pct^2 / (10000 * SCHED_CAPACITY_SCALE) [4]
+ *
+ */
+ /* equation [3] */
+ x = sum_util;
+ do_div(x, llc_weight);
+
+ /* equation [4] */
+ pct = env->sd->imbalance_pct;
+ tmp = x * x * pct * pct;
+ do_div(tmp, 10000 * SCHED_CAPACITY_SCALE);
+ tmp = min_t(long, tmp, SCHED_CAPACITY_SCALE);
+ y = SCHED_CAPACITY_SCALE - tmp;
+
+ /* equation [2] */
+ y *= llc_weight;
+ do_div(y, SCHED_CAPACITY_SCALE);
+ if ((int)y != sd_share->nr_idle_scan)
+ WRITE_ONCE(sd_share->nr_idle_scan, (int)y);
+}
+
+/**
+ * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
+ * @env: The load balancing environment.
+ * @sds: variable to hold the statistics for this sched_domain.
+ */
+
+static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
+{
+ struct sched_group *sg = env->sd->groups;
+ struct sg_lb_stats *local = &sds->local_stat;
+ struct sg_lb_stats tmp_sgs;
+ unsigned long sum_util = 0;
+ bool sg_overloaded = 0, sg_overutilized = 0;
+
+ do {
+ struct sg_lb_stats *sgs = &tmp_sgs;
+ int local_group;
+
+ local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
+ if (local_group) {
+ sds->local = sg;
+ sgs = local;
+
+ if (env->idle != CPU_NEWLY_IDLE ||
+ time_after_eq(jiffies, sg->sgc->next_update))
+ update_group_capacity(env->sd, env->dst_cpu);
+ }
+
+ update_sg_lb_stats(env, sds, sg, sgs, &sg_overloaded, &sg_overutilized);
+
+ if (!local_group && update_sd_pick_busiest(env, sds, sg, sgs)) {
+ sds->busiest = sg;
+ sds->busiest_stat = *sgs;
+ }
+
+ /* Now, start updating sd_lb_stats */
+ sds->total_load += sgs->group_load;
+ sds->total_capacity += sgs->group_capacity;
+
+ sum_util += sgs->group_util;
+ sg = sg->next;
+ } while (sg != env->sd->groups);
+
+ /*
+ * Indicate that the child domain of the busiest group prefers tasks
+ * go to a child's sibling domains first. NB the flags of a sched group
+ * are those of the child domain.
+ */
+ if (sds->busiest)
+ sds->prefer_sibling = !!(sds->busiest->flags & SD_PREFER_SIBLING);
+
+
+ if (env->sd->flags & SD_NUMA)
+ env->fbq_type = fbq_classify_group(&sds->busiest_stat);
+
+ if (!env->sd->parent) {
+ /* update overload indicator if we are at root domain */
+ set_rd_overloaded(env->dst_rq->rd, sg_overloaded);
+
+ /* Update over-utilization (tipping point, U >= 0) indicator */
+ set_rd_overutilized(env->dst_rq->rd, sg_overloaded);
+ } else if (sg_overutilized) {
+ set_rd_overutilized(env->dst_rq->rd, sg_overutilized);
+ }
+
+ update_idle_cpu_scan(env, sum_util);
+}
+
+/**
+ * calculate_imbalance - Calculate the amount of imbalance present within the
+ * groups of a given sched_domain during load balance.
+ * @env: load balance environment
+ * @sds: statistics of the sched_domain whose imbalance is to be calculated.
+ */
+static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
+{
+ struct sg_lb_stats *local, *busiest;
+
+ local = &sds->local_stat;
+ busiest = &sds->busiest_stat;
+
+ if (busiest->group_type == group_misfit_task) {
+ if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
+ /* Set imbalance to allow misfit tasks to be balanced. */
+ env->migration_type = migrate_misfit;
+ env->imbalance = 1;
+ } else {
+ /*
+ * Set load imbalance to allow moving task from cpu
+ * with reduced capacity.
+ */
+ env->migration_type = migrate_load;
+ env->imbalance = busiest->group_misfit_task_load;
+ }
+ return;
+ }
+
+ if (busiest->group_type == group_asym_packing) {
+ /*
+ * In case of asym capacity, we will try to migrate all load to
+ * the preferred CPU.
+ */
+ env->migration_type = migrate_task;
+ env->imbalance = busiest->sum_h_nr_running;
+ return;
+ }
+
+ if (busiest->group_type == group_smt_balance) {
+ /* Reduce number of tasks sharing CPU capacity */
+ env->migration_type = migrate_task;
+ env->imbalance = 1;
+ return;
+ }
+
+ if (busiest->group_type == group_imbalanced) {
+ /*
+ * In the group_imb case we cannot rely on group-wide averages
+ * to ensure CPU-load equilibrium, try to move any task to fix
+ * the imbalance. The next load balance will take care of
+ * balancing back the system.
+ */
+ env->migration_type = migrate_task;
+ env->imbalance = 1;
+ return;
+ }
+
+ /*
+ * Try to use spare capacity of local group without overloading it or
+ * emptying busiest.
+ */
+ if (local->group_type == group_has_spare) {
+ if ((busiest->group_type > group_fully_busy) &&
+ !(env->sd->flags & SD_SHARE_LLC)) {
+ /*
+ * If busiest is overloaded, try to fill spare
+ * capacity. This might end up creating spare capacity
+ * in busiest or busiest still being overloaded but
+ * there is no simple way to directly compute the
+ * amount of load to migrate in order to balance the
+ * system.
+ */
+ env->migration_type = migrate_util;
+ env->imbalance = max(local->group_capacity, local->group_util) -
+ local->group_util;
+
+ /*
+ * In some cases, the group's utilization is max or even
+ * higher than capacity because of migrations but the
+ * local CPU is (newly) idle. There is at least one
+ * waiting task in this overloaded busiest group. Let's
+ * try to pull it.
+ */
+ if (env->idle && env->imbalance == 0) {
+ env->migration_type = migrate_task;
+ env->imbalance = 1;
+ }
+
+ return;
+ }
+
+ if (busiest->group_weight == 1 || sds->prefer_sibling) {
+ /*
+ * When prefer sibling, evenly spread running tasks on
+ * groups.
+ */
+ env->migration_type = migrate_task;
+ env->imbalance = sibling_imbalance(env, sds, busiest, local);
+ } else {
+
+ /*
+ * If there is no overload, we just want to even the number of
+ * idle CPUs.
+ */
+ env->migration_type = migrate_task;
+ env->imbalance = max_t(long, 0,
+ (local->idle_cpus - busiest->idle_cpus));
+ }
+
+#ifdef CONFIG_NUMA
+ /* Consider allowing a small imbalance between NUMA groups */
+ if (env->sd->flags & SD_NUMA) {
+ env->imbalance = adjust_numa_imbalance(env->imbalance,
+ local->sum_nr_running + 1,
+ env->sd->imb_numa_nr);
+ }
+#endif
+
+ /* Number of tasks to move to restore balance */
+ env->imbalance >>= 1;
+
+ return;
+ }
+
+ /*
+ * Local is fully busy but has to take more load to relieve the
+ * busiest group
+ */
+ if (local->group_type < group_overloaded) {
+ /*
+ * Local will become overloaded so the avg_load metrics are
+ * finally needed.
+ */
+
+ local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) /
+ local->group_capacity;
+
+ /*
+ * If the local group is more loaded than the selected
+ * busiest group don't try to pull any tasks.
+ */
+ if (local->avg_load >= busiest->avg_load) {
+ env->imbalance = 0;
+ return;
+ }
+
+ sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
+ sds->total_capacity;
+
+ /*
+ * If the local group is more loaded than the average system
+ * load, don't try to pull any tasks.
+ */
+ if (local->avg_load >= sds->avg_load) {
+ env->imbalance = 0;
+ return;
+ }
+
+ }
+
+ /*
+ * Both group are or will become overloaded and we're trying to get all
+ * the CPUs to the average_load, so we don't want to push ourselves
+ * above the average load, nor do we wish to reduce the max loaded CPU
+ * below the average load. At the same time, we also don't want to
+ * reduce the group load below the group capacity. Thus we look for
+ * the minimum possible imbalance.
+ */
+ env->migration_type = migrate_load;
+ env->imbalance = min(
+ (busiest->avg_load - sds->avg_load) * busiest->group_capacity,
+ (sds->avg_load - local->avg_load) * local->group_capacity
+ ) / SCHED_CAPACITY_SCALE;
+}
+
+/******* sched_balance_find_src_group() helpers end here *********************/
+
+/*
+ * Decision matrix according to the local and busiest group type:
+ *
+ * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
+ * has_spare nr_idle balanced N/A N/A balanced balanced
+ * fully_busy nr_idle nr_idle N/A N/A balanced balanced
+ * misfit_task force N/A N/A N/A N/A N/A
+ * asym_packing force force N/A N/A force force
+ * imbalanced force force N/A N/A force force
+ * overloaded force force N/A N/A force avg_load
+ *
+ * N/A : Not Applicable because already filtered while updating
+ * statistics.
+ * balanced : The system is balanced for these 2 groups.
+ * force : Calculate the imbalance as load migration is probably needed.
+ * avg_load : Only if imbalance is significant enough.
+ * nr_idle : dst_cpu is not busy and the number of idle CPUs is quite
+ * different in groups.
+ */
+
+/**
+ * sched_balance_find_src_group - Returns the busiest group within the sched_domain
+ * if there is an imbalance.
+ * @env: The load balancing environment.
+ *
+ * Also calculates the amount of runnable load which should be moved
+ * to restore balance.
+ *
+ * Return: - The busiest group if imbalance exists.
+ */
+static struct sched_group *sched_balance_find_src_group(struct lb_env *env)
+{
+ struct sg_lb_stats *local, *busiest;
+ struct sd_lb_stats sds;
+
+ init_sd_lb_stats(&sds);
+
+ /*
+ * Compute the various statistics relevant for load balancing at
+ * this level.
+ */
+ update_sd_lb_stats(env, &sds);
+
+ /* There is no busy sibling group to pull tasks from */
+ if (!sds.busiest)
+ goto out_balanced;
+
+ busiest = &sds.busiest_stat;
+
+ /* Misfit tasks should be dealt with regardless of the avg load */
+ if (busiest->group_type == group_misfit_task)
+ goto force_balance;
+
+ if (!is_rd_overutilized(env->dst_rq->rd) &&
+ rcu_dereference(env->dst_rq->rd->pd))
+ goto out_balanced;
+
+ /* ASYM feature bypasses nice load balance check */
+ if (busiest->group_type == group_asym_packing)
+ goto force_balance;
+
+ /*
+ * If the busiest group is imbalanced the below checks don't
+ * work because they assume all things are equal, which typically
+ * isn't true due to cpus_ptr constraints and the like.
+ */
+ if (busiest->group_type == group_imbalanced)
+ goto force_balance;
+
+ local = &sds.local_stat;
+ /*
+ * If the local group is busier than the selected busiest group
+ * don't try and pull any tasks.
+ */
+ if (local->group_type > busiest->group_type)
+ goto out_balanced;
+
+ /*
+ * When groups are overloaded, use the avg_load to ensure fairness
+ * between tasks.
+ */
+ if (local->group_type == group_overloaded) {
+ /*
+ * If the local group is more loaded than the selected
+ * busiest group don't try to pull any tasks.
+ */
+ if (local->avg_load >= busiest->avg_load)
+ goto out_balanced;
+
+ /* XXX broken for overlapping NUMA groups */
+ sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) /
+ sds.total_capacity;
+
+ /*
+ * Don't pull any tasks if this group is already above the
+ * domain average load.
+ */
+ if (local->avg_load >= sds.avg_load)
+ goto out_balanced;
+
+ /*
+ * If the busiest group is more loaded, use imbalance_pct to be
+ * conservative.
+ */
+ if (100 * busiest->avg_load <=
+ env->sd->imbalance_pct * local->avg_load)
+ goto out_balanced;
+ }
+
+ /*
+ * Try to move all excess tasks to a sibling domain of the busiest
+ * group's child domain.
+ */
+ if (sds.prefer_sibling && local->group_type == group_has_spare &&
+ sibling_imbalance(env, &sds, busiest, local) > 1)
+ goto force_balance;
+
+ if (busiest->group_type != group_overloaded) {
+ if (!env->idle) {
+ /*
+ * If the busiest group is not overloaded (and as a
+ * result the local one too) but this CPU is already
+ * busy, let another idle CPU try to pull task.
+ */
+ goto out_balanced;
+ }
+
+ if (busiest->group_type == group_smt_balance &&
+ smt_vs_nonsmt_groups(sds.local, sds.busiest)) {
+ /* Let non SMT CPU pull from SMT CPU sharing with sibling */
+ goto force_balance;
+ }
+
+ if (busiest->group_weight > 1 &&
+ local->idle_cpus <= (busiest->idle_cpus + 1)) {
+ /*
+ * If the busiest group is not overloaded
+ * and there is no imbalance between this and busiest
+ * group wrt idle CPUs, it is balanced. The imbalance
+ * becomes significant if the diff is greater than 1
+ * otherwise we might end up to just move the imbalance
+ * on another group. Of course this applies only if
+ * there is more than 1 CPU per group.
+ */
+ goto out_balanced;
+ }
+
+ if (busiest->sum_h_nr_running == 1) {
+ /*
+ * busiest doesn't have any tasks waiting to run
+ */
+ goto out_balanced;
+ }
+ }
+
+force_balance:
+ /* Looks like there is an imbalance. Compute it */
+ calculate_imbalance(env, &sds);
+ return env->imbalance ? sds.busiest : NULL;
+
+out_balanced:
+ env->imbalance = 0;
+ return NULL;
+}
+
+/*
+ * sched_balance_find_src_rq - find the busiest runqueue among the CPUs in the group.
+ */
+static struct rq *sched_balance_find_src_rq(struct lb_env *env,
+ struct sched_group *group)
+{
+ struct rq *busiest = NULL, *rq;
+ unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
+ unsigned int busiest_nr = 0;
+ int i;
+
+ for_each_cpu_and(i, sched_group_span(group), env->cpus) {
+ unsigned long capacity, load, util;
+ unsigned int nr_running;
+ enum fbq_type rt;
+
+ rq = cpu_rq(i);
+ rt = fbq_classify_rq(rq);
+
+ /*
+ * We classify groups/runqueues into three groups:
+ * - regular: there are !numa tasks
+ * - remote: there are numa tasks that run on the 'wrong' node
+ * - all: there is no distinction
+ *
+ * In order to avoid migrating ideally placed numa tasks,
+ * ignore those when there's better options.
+ *
+ * If we ignore the actual busiest queue to migrate another
+ * task, the next balance pass can still reduce the busiest
+ * queue by moving tasks around inside the node.
+ *
+ * If we cannot move enough load due to this classification
+ * the next pass will adjust the group classification and
+ * allow migration of more tasks.
+ *
+ * Both cases only affect the total convergence complexity.
+ */
+ if (rt > env->fbq_type)
+ continue;
+
+ nr_running = rq->cfs.h_nr_running;
+ if (!nr_running)
+ continue;
+
+ capacity = capacity_of(i);
+
+ /*
+ * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
+ * eventually lead to active_balancing high->low capacity.
+ * Higher per-CPU capacity is considered better than balancing
+ * average load.
+ */
+ if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
+ !capacity_greater(capacity_of(env->dst_cpu), capacity) &&
+ nr_running == 1)
+ continue;
+
+ /*
+ * Make sure we only pull tasks from a CPU of lower priority
+ * when balancing between SMT siblings.
+ *
+ * If balancing between cores, let lower priority CPUs help
+ * SMT cores with more than one busy sibling.
+ */
+ if (sched_asym(env->sd, i, env->dst_cpu) && nr_running == 1)
+ continue;
+
+ switch (env->migration_type) {
+ case migrate_load:
+ /*
+ * When comparing with load imbalance, use cpu_load()
+ * which is not scaled with the CPU capacity.
+ */
+ load = cpu_load(rq);
+
+ if (nr_running == 1 && load > env->imbalance &&
+ !check_cpu_capacity(rq, env->sd))
+ break;
+
+ /*
+ * For the load comparisons with the other CPUs,
+ * consider the cpu_load() scaled with the CPU
+ * capacity, so that the load can be moved away
+ * from the CPU that is potentially running at a
+ * lower capacity.
+ *
+ * Thus we're looking for max(load_i / capacity_i),
+ * crosswise multiplication to rid ourselves of the
+ * division works out to:
+ * load_i * capacity_j > load_j * capacity_i;
+ * where j is our previous maximum.
+ */
+ if (load * busiest_capacity > busiest_load * capacity) {
+ busiest_load = load;
+ busiest_capacity = capacity;
+ busiest = rq;
+ }
+ break;
+
+ case migrate_util:
+ util = cpu_util_cfs_boost(i);
+
+ /*
+ * Don't try to pull utilization from a CPU with one
+ * running task. Whatever its utilization, we will fail
+ * detach the task.
+ */
+ if (nr_running <= 1)
+ continue;
+
+ if (busiest_util < util) {
+ busiest_util = util;
+ busiest = rq;
+ }
+ break;
+
+ case migrate_task:
+ if (busiest_nr < nr_running) {
+ busiest_nr = nr_running;
+ busiest = rq;
+ }
+ break;
+
+ case migrate_misfit:
+ /*
+ * For ASYM_CPUCAPACITY domains with misfit tasks we
+ * simply seek the "biggest" misfit task.
+ */
+ if (rq->misfit_task_load > busiest_load) {
+ busiest_load = rq->misfit_task_load;
+ busiest = rq;
+ }
+
+ break;
+
+ }
+ }
+
+ return busiest;
+}
+
+/*
+ * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
+ * so long as it is large enough.
+ */
+#define MAX_PINNED_INTERVAL 512
+
+static inline bool
+asym_active_balance(struct lb_env *env)
+{
+ /*
+ * ASYM_PACKING needs to force migrate tasks from busy but lower
+ * priority CPUs in order to pack all tasks in the highest priority
+ * CPUs. When done between cores, do it only if the whole core if the
+ * whole core is idle.
+ *
+ * If @env::src_cpu is an SMT core with busy siblings, let
+ * the lower priority @env::dst_cpu help it. Do not follow
+ * CPU priority.
+ */
+ return env->idle && sched_use_asym_prio(env->sd, env->dst_cpu) &&
+ (sched_asym_prefer(env->dst_cpu, env->src_cpu) ||
+ !sched_use_asym_prio(env->sd, env->src_cpu));
+}
+
+static inline bool
+imbalanced_active_balance(struct lb_env *env)
+{
+ struct sched_domain *sd = env->sd;
+
+ /*
+ * The imbalanced case includes the case of pinned tasks preventing a fair
+ * distribution of the load on the system but also the even distribution of the
+ * threads on a system with spare capacity
+ */
+ if ((env->migration_type == migrate_task) &&
+ (sd->nr_balance_failed > sd->cache_nice_tries+2))
+ return 1;
+
+ return 0;
+}
+
+static int need_active_balance(struct lb_env *env)
+{
+ struct sched_domain *sd = env->sd;
+
+ if (asym_active_balance(env))
+ return 1;
+
+ if (imbalanced_active_balance(env))
+ return 1;
+
+ /*
+ * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
+ * It's worth migrating the task if the src_cpu's capacity is reduced
+ * because of other sched_class or IRQs if more capacity stays
+ * available on dst_cpu.
+ */
+ if (env->idle &&
+ (env->src_rq->cfs.h_nr_running == 1)) {
+ if ((check_cpu_capacity(env->src_rq, sd)) &&
+ (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
+ return 1;
+ }
+
+ if (env->migration_type == migrate_misfit)
+ return 1;
+
+ return 0;
+}
+
+static int active_load_balance_cpu_stop(void *data);
+
+static int should_we_balance(struct lb_env *env)
+{
+ struct cpumask *swb_cpus = this_cpu_cpumask_var_ptr(should_we_balance_tmpmask);
+ struct sched_group *sg = env->sd->groups;
+ int cpu, idle_smt = -1;
+
+ /*
+ * Ensure the balancing environment is consistent; can happen
+ * when the softirq triggers 'during' hotplug.
+ */
+ if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
+ return 0;
+
+ /*
+ * In the newly idle case, we will allow all the CPUs
+ * to do the newly idle load balance.
+ *
+ * However, we bail out if we already have tasks or a wakeup pending,
+ * to optimize wakeup latency.
+ */
+ if (env->idle == CPU_NEWLY_IDLE) {
+ if (env->dst_rq->nr_running > 0 || env->dst_rq->ttwu_pending)
+ return 0;
+ return 1;
+ }
+
+ cpumask_copy(swb_cpus, group_balance_mask(sg));
+ /* Try to find first idle CPU */
+ for_each_cpu_and(cpu, swb_cpus, env->cpus) {
+ if (!idle_cpu(cpu))
+ continue;
+
+ /*
+ * Don't balance to idle SMT in busy core right away when
+ * balancing cores, but remember the first idle SMT CPU for
+ * later consideration. Find CPU on an idle core first.
+ */
+ if (!(env->sd->flags & SD_SHARE_CPUCAPACITY) && !is_core_idle(cpu)) {
+ if (idle_smt == -1)
+ idle_smt = cpu;
+ /*
+ * If the core is not idle, and first SMT sibling which is
+ * idle has been found, then its not needed to check other
+ * SMT siblings for idleness:
+ */
+#ifdef CONFIG_SCHED_SMT
+ cpumask_andnot(swb_cpus, swb_cpus, cpu_smt_mask(cpu));
+#endif
+ continue;
+ }
+
+ /*
+ * Are we the first idle core in a non-SMT domain or higher,
+ * or the first idle CPU in a SMT domain?
+ */
+ return cpu == env->dst_cpu;
+ }
+
+ /* Are we the first idle CPU with busy siblings? */
+ if (idle_smt != -1)
+ return idle_smt == env->dst_cpu;
+
+ /* Are we the first CPU of this group ? */
+ return group_balance_cpu(sg) == env->dst_cpu;
+}
+
+/*
+ * Check this_cpu to ensure it is balanced within domain. Attempt to move
+ * tasks if there is an imbalance.
+ */
+static int sched_balance_rq(int this_cpu, struct rq *this_rq,
+ struct sched_domain *sd, enum cpu_idle_type idle,
+ int *continue_balancing)
+{
+ int ld_moved, cur_ld_moved, active_balance = 0;
+ struct sched_domain *sd_parent = sd->parent;
+ struct sched_group *group;
+ struct rq *busiest;
+ struct rq_flags rf;
+ struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
+ struct lb_env env = {
+ .sd = sd,
+ .dst_cpu = this_cpu,
+ .dst_rq = this_rq,
+ .dst_grpmask = group_balance_mask(sd->groups),
+ .idle = idle,
+ .loop_break = SCHED_NR_MIGRATE_BREAK,
+ .cpus = cpus,
+ .fbq_type = all,
+ .tasks = LIST_HEAD_INIT(env.tasks),
+ };
+
+ cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
+
+ schedstat_inc(sd->lb_count[idle]);
+
+redo:
+ if (!should_we_balance(&env)) {
+ *continue_balancing = 0;
+ goto out_balanced;
+ }
+
+ group = sched_balance_find_src_group(&env);
+ if (!group) {
+ schedstat_inc(sd->lb_nobusyg[idle]);
+ goto out_balanced;
+ }
+
+ busiest = sched_balance_find_src_rq(&env, group);
+ if (!busiest) {
+ schedstat_inc(sd->lb_nobusyq[idle]);
+ goto out_balanced;
+ }
+
+ WARN_ON_ONCE(busiest == env.dst_rq);
+
+ schedstat_add(sd->lb_imbalance[idle], env.imbalance);
+
+ env.src_cpu = busiest->cpu;
+ env.src_rq = busiest;
+
+ ld_moved = 0;
+ /* Clear this flag as soon as we find a pullable task */
+ env.flags |= LBF_ALL_PINNED;
+ if (busiest->nr_running > 1) {
+ /*
+ * Attempt to move tasks. If sched_balance_find_src_group has found
+ * an imbalance but busiest->nr_running <= 1, the group is
+ * still unbalanced. ld_moved simply stays zero, so it is
+ * correctly treated as an imbalance.
+ */
+ env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
+
+more_balance:
+ rq_lock_irqsave(busiest, &rf);
+ update_rq_clock(busiest);
+
+ /*
+ * cur_ld_moved - load moved in current iteration
+ * ld_moved - cumulative load moved across iterations
+ */
+ cur_ld_moved = detach_tasks(&env);
+
+ /*
+ * We've detached some tasks from busiest_rq. Every
+ * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
+ * unlock busiest->lock, and we are able to be sure
+ * that nobody can manipulate the tasks in parallel.
+ * See task_rq_lock() family for the details.
+ */
+
+ rq_unlock(busiest, &rf);
+
+ if (cur_ld_moved) {
+ attach_tasks(&env);
+ ld_moved += cur_ld_moved;
+ }
+
+ local_irq_restore(rf.flags);
+
+ if (env.flags & LBF_NEED_BREAK) {
+ env.flags &= ~LBF_NEED_BREAK;
+ /* Stop if we tried all running tasks */
+ if (env.loop < busiest->nr_running)
+ goto more_balance;
+ }
+
+ /*
+ * Revisit (affine) tasks on src_cpu that couldn't be moved to
+ * us and move them to an alternate dst_cpu in our sched_group
+ * where they can run. The upper limit on how many times we
+ * iterate on same src_cpu is dependent on number of CPUs in our
+ * sched_group.
+ *
+ * This changes load balance semantics a bit on who can move
+ * load to a given_cpu. In addition to the given_cpu itself
+ * (or a ilb_cpu acting on its behalf where given_cpu is
+ * nohz-idle), we now have balance_cpu in a position to move
+ * load to given_cpu. In rare situations, this may cause
+ * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
+ * _independently_ and at _same_ time to move some load to
+ * given_cpu) causing excess load to be moved to given_cpu.
+ * This however should not happen so much in practice and
+ * moreover subsequent load balance cycles should correct the
+ * excess load moved.
+ */
+ if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
+
+ /* Prevent to re-select dst_cpu via env's CPUs */
+ __cpumask_clear_cpu(env.dst_cpu, env.cpus);
+
+ env.dst_rq = cpu_rq(env.new_dst_cpu);
+ env.dst_cpu = env.new_dst_cpu;
+ env.flags &= ~LBF_DST_PINNED;
+ env.loop = 0;
+ env.loop_break = SCHED_NR_MIGRATE_BREAK;
+
+ /*
+ * Go back to "more_balance" rather than "redo" since we
+ * need to continue with same src_cpu.
+ */
+ goto more_balance;
+ }
+
+ /*
+ * We failed to reach balance because of affinity.
+ */
+ if (sd_parent) {
+ int *group_imbalance = &sd_parent->groups->sgc->imbalance;
+
+ if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
+ *group_imbalance = 1;
+ }
+
+ /* All tasks on this runqueue were pinned by CPU affinity */
+ if (unlikely(env.flags & LBF_ALL_PINNED)) {
+ __cpumask_clear_cpu(cpu_of(busiest), cpus);
+ /*
+ * Attempting to continue load balancing at the current
+ * sched_domain level only makes sense if there are
+ * active CPUs remaining as possible busiest CPUs to
+ * pull load from which are not contained within the
+ * destination group that is receiving any migrated
+ * load.
+ */
+ if (!cpumask_subset(cpus, env.dst_grpmask)) {
+ env.loop = 0;
+ env.loop_break = SCHED_NR_MIGRATE_BREAK;
+ goto redo;
+ }
+ goto out_all_pinned;
+ }
+ }
+
+ if (!ld_moved) {
+ schedstat_inc(sd->lb_failed[idle]);
+ /*
+ * Increment the failure counter only on periodic balance.
+ * We do not want newidle balance, which can be very
+ * frequent, pollute the failure counter causing
+ * excessive cache_hot migrations and active balances.
+ *
+ * Similarly for migration_misfit which is not related to
+ * load/util migration, don't pollute nr_balance_failed.
+ */
+ if (idle != CPU_NEWLY_IDLE &&
+ env.migration_type != migrate_misfit)
+ sd->nr_balance_failed++;
+
+ if (need_active_balance(&env)) {
+ unsigned long flags;
+
+ raw_spin_rq_lock_irqsave(busiest, flags);
+
+ /*
+ * Don't kick the active_load_balance_cpu_stop,
+ * if the curr task on busiest CPU can't be
+ * moved to this_cpu:
+ */
+ if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
+ raw_spin_rq_unlock_irqrestore(busiest, flags);
+ goto out_one_pinned;
+ }
+
+ /* Record that we found at least one task that could run on this_cpu */
+ env.flags &= ~LBF_ALL_PINNED;
+
+ /*
+ * ->active_balance synchronizes accesses to
+ * ->active_balance_work. Once set, it's cleared
+ * only after active load balance is finished.
+ */
+ if (!busiest->active_balance) {
+ busiest->active_balance = 1;
+ busiest->push_cpu = this_cpu;
+ active_balance = 1;
+ }
+
+ preempt_disable();
+ raw_spin_rq_unlock_irqrestore(busiest, flags);
+ if (active_balance) {
+ stop_one_cpu_nowait(cpu_of(busiest),
+ active_load_balance_cpu_stop, busiest,
+ &busiest->active_balance_work);
+ }
+ preempt_enable();
+ }
+ } else {
+ sd->nr_balance_failed = 0;
+ }
+
+ if (likely(!active_balance) || need_active_balance(&env)) {
+ /* We were unbalanced, so reset the balancing interval */
+ sd->balance_interval = sd->min_interval;
+ }
+
+ goto out;
+
+out_balanced:
+ /*
+ * We reach balance although we may have faced some affinity
+ * constraints. Clear the imbalance flag only if other tasks got
+ * a chance to move and fix the imbalance.
+ */
+ if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
+ int *group_imbalance = &sd_parent->groups->sgc->imbalance;
+
+ if (*group_imbalance)
+ *group_imbalance = 0;
+ }
+
+out_all_pinned:
+ /*
+ * We reach balance because all tasks are pinned at this level so
+ * we can't migrate them. Let the imbalance flag set so parent level
+ * can try to migrate them.
+ */
+ schedstat_inc(sd->lb_balanced[idle]);
+
+ sd->nr_balance_failed = 0;
+
+out_one_pinned:
+ ld_moved = 0;
+
+ /*
+ * sched_balance_newidle() disregards balance intervals, so we could
+ * repeatedly reach this code, which would lead to balance_interval
+ * skyrocketing in a short amount of time. Skip the balance_interval
+ * increase logic to avoid that.
+ *
+ * Similarly misfit migration which is not necessarily an indication of
+ * the system being busy and requires lb to backoff to let it settle
+ * down.
+ */
+ if (env.idle == CPU_NEWLY_IDLE ||
+ env.migration_type == migrate_misfit)
+ goto out;
+
+ /* tune up the balancing interval */
+ if ((env.flags & LBF_ALL_PINNED &&
+ sd->balance_interval < MAX_PINNED_INTERVAL) ||
+ sd->balance_interval < sd->max_interval)
+ sd->balance_interval *= 2;
+out:
+ return ld_moved;
+}
+
+static inline unsigned long
+get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
+{
+ unsigned long interval = sd->balance_interval;
+
+ if (cpu_busy)
+ interval *= sd->busy_factor;
+
+ /* scale ms to jiffies */
+ interval = msecs_to_jiffies(interval);
+
+ /*
+ * Reduce likelihood of busy balancing at higher domains racing with
+ * balancing at lower domains by preventing their balancing periods
+ * from being multiples of each other.
+ */
+ if (cpu_busy)
+ interval -= 1;
+
+ interval = clamp(interval, 1UL, max_load_balance_interval);
+
+ return interval;
+}
+
+static inline void
+update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
+{
+ unsigned long interval, next;
+
+ /* used by idle balance, so cpu_busy = 0 */
+ interval = get_sd_balance_interval(sd, 0);
+ next = sd->last_balance + interval;
+
+ if (time_after(*next_balance, next))
+ *next_balance = next;
+}
+
+/*
+ * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
+ * running tasks off the busiest CPU onto idle CPUs. It requires at
+ * least 1 task to be running on each physical CPU where possible, and
+ * avoids physical / logical imbalances.
+ */
+static int active_load_balance_cpu_stop(void *data)
+{
+ struct rq *busiest_rq = data;
+ int busiest_cpu = cpu_of(busiest_rq);
+ int target_cpu = busiest_rq->push_cpu;
+ struct rq *target_rq = cpu_rq(target_cpu);
+ struct sched_domain *sd;
+ struct task_struct *p = NULL;
+ struct rq_flags rf;
+
+ rq_lock_irq(busiest_rq, &rf);
+ /*
+ * Between queueing the stop-work and running it is a hole in which
+ * CPUs can become inactive. We should not move tasks from or to
+ * inactive CPUs.
+ */
+ if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
+ goto out_unlock;
+
+ /* Make sure the requested CPU hasn't gone down in the meantime: */
+ if (unlikely(busiest_cpu != smp_processor_id() ||
+ !busiest_rq->active_balance))
+ goto out_unlock;
+
+ /* Is there any task to move? */
+ if (busiest_rq->nr_running <= 1)
+ goto out_unlock;
+
+ /*
+ * This condition is "impossible", if it occurs
+ * we need to fix it. Originally reported by
+ * Bjorn Helgaas on a 128-CPU setup.
+ */
+ WARN_ON_ONCE(busiest_rq == target_rq);
+
+ /* Search for an sd spanning us and the target CPU. */
+ rcu_read_lock();
+ for_each_domain(target_cpu, sd) {
+ if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
+ break;
+ }
+
+ if (likely(sd)) {
+ struct lb_env env = {
+ .sd = sd,
+ .dst_cpu = target_cpu,
+ .dst_rq = target_rq,
+ .src_cpu = busiest_rq->cpu,
+ .src_rq = busiest_rq,
+ .idle = CPU_IDLE,
+ .flags = LBF_ACTIVE_LB,
+ };
+
+ schedstat_inc(sd->alb_count);
+ update_rq_clock(busiest_rq);
+
+ p = detach_one_task(&env);
+ if (p) {
+ schedstat_inc(sd->alb_pushed);
+ /* Active balancing done, reset the failure counter. */
+ sd->nr_balance_failed = 0;
+ } else {
+ schedstat_inc(sd->alb_failed);
+ }
+ }
+ rcu_read_unlock();
+out_unlock:
+ busiest_rq->active_balance = 0;
+ rq_unlock(busiest_rq, &rf);
+
+ if (p)
+ attach_one_task(target_rq, p);
+
+ local_irq_enable();
+
+ return 0;
+}
+
+/*
+ * This flag serializes load-balancing passes over large domains
+ * (above the NODE topology level) - only one load-balancing instance
+ * may run at a time, to reduce overhead on very large systems with
+ * lots of CPUs and large NUMA distances.
+ *
+ * - Note that load-balancing passes triggered while another one
+ * is executing are skipped and not re-tried.
+ *
+ * - Also note that this does not serialize rebalance_domains()
+ * execution, as non-SD_SERIALIZE domains will still be
+ * load-balanced in parallel.
+ */
+static atomic_t sched_balance_running = ATOMIC_INIT(0);
+
+/*
+ * Scale the max sched_balance_rq interval with the number of CPUs in the system.
+ * This trades load-balance latency on larger machines for less cross talk.
+ */
+void update_max_interval(void)
+{
+ max_load_balance_interval = HZ*num_online_cpus()/10;
+}
+
+static inline bool update_newidle_cost(struct sched_domain *sd, u64 cost)
+{
+ if (cost > sd->max_newidle_lb_cost) {
+ /*
+ * Track max cost of a domain to make sure to not delay the
+ * next wakeup on the CPU.
+ */
+ sd->max_newidle_lb_cost = cost;
+ sd->last_decay_max_lb_cost = jiffies;
+ } else if (time_after(jiffies, sd->last_decay_max_lb_cost + HZ)) {
+ /*
+ * Decay the newidle max times by ~1% per second to ensure that
+ * it is not outdated and the current max cost is actually
+ * shorter.
+ */
+ sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 253) / 256;
+ sd->last_decay_max_lb_cost = jiffies;
+
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * It checks each scheduling domain to see if it is due to be balanced,
+ * and initiates a balancing operation if so.
+ *
+ * Balancing parameters are set up in init_sched_domains.
+ */
+static void sched_balance_domains(struct rq *rq, enum cpu_idle_type idle)
+{
+ int continue_balancing = 1;
+ int cpu = rq->cpu;
+ int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
+ unsigned long interval;
+ struct sched_domain *sd;
+ /* Earliest time when we have to do rebalance again */
+ unsigned long next_balance = jiffies + 60*HZ;
+ int update_next_balance = 0;
+ int need_serialize, need_decay = 0;
+ u64 max_cost = 0;
+
+ rcu_read_lock();
+ for_each_domain(cpu, sd) {
+ /*
+ * Decay the newidle max times here because this is a regular
+ * visit to all the domains.
+ */
+ need_decay = update_newidle_cost(sd, 0);
+ max_cost += sd->max_newidle_lb_cost;
+
+ /*
+ * Stop the load balance at this level. There is another
+ * CPU in our sched group which is doing load balancing more
+ * actively.
+ */
+ if (!continue_balancing) {
+ if (need_decay)
+ continue;
+ break;
+ }
+
+ interval = get_sd_balance_interval(sd, busy);
+
+ need_serialize = sd->flags & SD_SERIALIZE;
+ if (need_serialize) {
+ if (atomic_cmpxchg_acquire(&sched_balance_running, 0, 1))
+ goto out;
+ }
+
+ if (time_after_eq(jiffies, sd->last_balance + interval)) {
+ if (sched_balance_rq(cpu, rq, sd, idle, &continue_balancing)) {
+ /*
+ * The LBF_DST_PINNED logic could have changed
+ * env->dst_cpu, so we can't know our idle
+ * state even if we migrated tasks. Update it.
+ */
+ idle = idle_cpu(cpu);
+ busy = !idle && !sched_idle_cpu(cpu);
+ }
+ sd->last_balance = jiffies;
+ interval = get_sd_balance_interval(sd, busy);
+ }
+ if (need_serialize)
+ atomic_set_release(&sched_balance_running, 0);
+out:
+ if (time_after(next_balance, sd->last_balance + interval)) {
+ next_balance = sd->last_balance + interval;
+ update_next_balance = 1;
+ }
+ }
+ if (need_decay) {
+ /*
+ * Ensure the rq-wide value also decays but keep it at a
+ * reasonable floor to avoid funnies with rq->avg_idle.
+ */
+ rq->max_idle_balance_cost =
+ max((u64)sysctl_sched_migration_cost, max_cost);
+ }
+ rcu_read_unlock();
+
+ /*
+ * next_balance will be updated only when there is a need.
+ * When the cpu is attached to null domain for ex, it will not be
+ * updated.
+ */
+ if (likely(update_next_balance))
+ rq->next_balance = next_balance;
+
+}
+
+static inline int on_null_domain(struct rq *rq)
+{
+ return unlikely(!rcu_dereference_sched(rq->sd));
+}
+
+#ifdef CONFIG_NO_HZ_COMMON
+/*
+ * NOHZ idle load balancing (ILB) details:
+ *
+ * - When one of the busy CPUs notices that there may be an idle rebalancing
+ * needed, they will kick the idle load balancer, which then does idle
+ * load balancing for all the idle CPUs.
+ *
+ * - HK_TYPE_MISC CPUs are used for this task, because HK_TYPE_SCHED is not set
+ * anywhere yet.
+ */
+static inline int find_new_ilb(void)
+{
+ const struct cpumask *hk_mask;
+ int ilb_cpu;
+
+ hk_mask = housekeeping_cpumask(HK_TYPE_MISC);
+
+ for_each_cpu_and(ilb_cpu, nohz.idle_cpus_mask, hk_mask) {
+
+ if (ilb_cpu == smp_processor_id())
+ continue;
+
+ if (idle_cpu(ilb_cpu))
+ return ilb_cpu;
+ }
+
+ return -1;
+}
+
+/*
+ * Kick a CPU to do the NOHZ balancing, if it is time for it, via a cross-CPU
+ * SMP function call (IPI).
+ *
+ * We pick the first idle CPU in the HK_TYPE_MISC housekeeping set (if there is one).
+ */
+static void kick_ilb(unsigned int flags)
+{
+ int ilb_cpu;
+
+ /*
+ * Increase nohz.next_balance only when if full ilb is triggered but
+ * not if we only update stats.
+ */
+ if (flags & NOHZ_BALANCE_KICK)
+ nohz.next_balance = jiffies+1;
+
+ ilb_cpu = find_new_ilb();
+ if (ilb_cpu < 0)
+ return;
+
+ /*
+ * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
+ * the first flag owns it; cleared by nohz_csd_func().
+ */
+ flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
+ if (flags & NOHZ_KICK_MASK)
+ return;
+
+ /*
+ * This way we generate an IPI on the target CPU which
+ * is idle, and the softirq performing NOHZ idle load balancing
+ * will be run before returning from the IPI.
+ */
+ smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd);
+}
+
+/*
+ * Current decision point for kicking the idle load balancer in the presence
+ * of idle CPUs in the system.
+ */
+static void nohz_balancer_kick(struct rq *rq)
+{
+ unsigned long now = jiffies;
+ struct sched_domain_shared *sds;
+ struct sched_domain *sd;
+ int nr_busy, i, cpu = rq->cpu;
+ unsigned int flags = 0;
+
+ if (unlikely(rq->idle_balance))
+ return;
+
+ /*
+ * We may be recently in ticked or tickless idle mode. At the first
+ * busy tick after returning from idle, we will update the busy stats.
+ */
+ nohz_balance_exit_idle(rq);
+
+ /*
+ * None are in tickless mode and hence no need for NOHZ idle load
+ * balancing:
+ */
+ if (likely(!atomic_read(&nohz.nr_cpus)))
+ return;
+
+ if (READ_ONCE(nohz.has_blocked) &&
+ time_after(now, READ_ONCE(nohz.next_blocked)))
+ flags = NOHZ_STATS_KICK;
+
+ if (time_before(now, nohz.next_balance))
+ goto out;
+
+ if (rq->nr_running >= 2) {
+ flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
+ goto out;
+ }
+
+ rcu_read_lock();
+
+ sd = rcu_dereference(rq->sd);
+ if (sd) {
+ /*
+ * If there's a runnable CFS task and the current CPU has reduced
+ * capacity, kick the ILB to see if there's a better CPU to run on:
+ */
+ if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
+ flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
+ goto unlock;
+ }
+ }
+
+ sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
+ if (sd) {
+ /*
+ * When ASYM_PACKING; see if there's a more preferred CPU
+ * currently idle; in which case, kick the ILB to move tasks
+ * around.
+ *
+ * When balancing between cores, all the SMT siblings of the
+ * preferred CPU must be idle.
+ */
+ for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
+ if (sched_asym(sd, i, cpu)) {
+ flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
+ goto unlock;
+ }
+ }
+ }
+
+ sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
+ if (sd) {
+ /*
+ * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
+ * to run the misfit task on.
+ */
+ if (check_misfit_status(rq)) {
+ flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
+ goto unlock;
+ }
+
+ /*
+ * For asymmetric systems, we do not want to nicely balance
+ * cache use, instead we want to embrace asymmetry and only
+ * ensure tasks have enough CPU capacity.
+ *
+ * Skip the LLC logic because it's not relevant in that case.
+ */
+ goto unlock;
+ }
+
+ sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
+ if (sds) {
+ /*
+ * If there is an imbalance between LLC domains (IOW we could
+ * increase the overall cache utilization), we need a less-loaded LLC
+ * domain to pull some load from. Likewise, we may need to spread
+ * load within the current LLC domain (e.g. packed SMT cores but
+ * other CPUs are idle). We can't really know from here how busy
+ * the others are - so just get a NOHZ balance going if it looks
+ * like this LLC domain has tasks we could move.
+ */
+ nr_busy = atomic_read(&sds->nr_busy_cpus);
+ if (nr_busy > 1) {
+ flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
+ goto unlock;
+ }
+ }
+unlock:
+ rcu_read_unlock();
+out:
+ if (READ_ONCE(nohz.needs_update))
+ flags |= NOHZ_NEXT_KICK;
+
+ if (flags)
+ kick_ilb(flags);
+}
+
+static void set_cpu_sd_state_busy(int cpu)
+{
+ struct sched_domain *sd;
+
+ rcu_read_lock();
+ sd = rcu_dereference(per_cpu(sd_llc, cpu));
+
+ if (!sd || !sd->nohz_idle)
+ goto unlock;
+ sd->nohz_idle = 0;
+
+ atomic_inc(&sd->shared->nr_busy_cpus);
+unlock:
+ rcu_read_unlock();
+}
+
+void nohz_balance_exit_idle(struct rq *rq)
+{
+ SCHED_WARN_ON(rq != this_rq());
+
+ if (likely(!rq->nohz_tick_stopped))
+ return;
+
+ rq->nohz_tick_stopped = 0;
+ cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
+ atomic_dec(&nohz.nr_cpus);
+
+ set_cpu_sd_state_busy(rq->cpu);
+}
+
+static void set_cpu_sd_state_idle(int cpu)
+{
+ struct sched_domain *sd;
+
+ rcu_read_lock();
+ sd = rcu_dereference(per_cpu(sd_llc, cpu));
+
+ if (!sd || sd->nohz_idle)
+ goto unlock;
+ sd->nohz_idle = 1;
+
+ atomic_dec(&sd->shared->nr_busy_cpus);
+unlock:
+ rcu_read_unlock();
+}
+
+/*
+ * This routine will record that the CPU is going idle with tick stopped.
+ * This info will be used in performing idle load balancing in the future.
+ */
+void nohz_balance_enter_idle(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ SCHED_WARN_ON(cpu != smp_processor_id());
+
+ /* If this CPU is going down, then nothing needs to be done: */
+ if (!cpu_active(cpu))
+ return;
+
+ /* Spare idle load balancing on CPUs that don't want to be disturbed: */
+ if (!housekeeping_cpu(cpu, HK_TYPE_SCHED))
+ return;
+
+ /*
+ * Can be set safely without rq->lock held
+ * If a clear happens, it will have evaluated last additions because
+ * rq->lock is held during the check and the clear
+ */
+ rq->has_blocked_load = 1;
+
+ /*
+ * The tick is still stopped but load could have been added in the
+ * meantime. We set the nohz.has_blocked flag to trig a check of the
+ * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
+ * of nohz.has_blocked can only happen after checking the new load
+ */
+ if (rq->nohz_tick_stopped)
+ goto out;
+
+ /* If we're a completely isolated CPU, we don't play: */
+ if (on_null_domain(rq))
+ return;
+
+ rq->nohz_tick_stopped = 1;
+
+ cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
+ atomic_inc(&nohz.nr_cpus);
+
+ /*
+ * Ensures that if nohz_idle_balance() fails to observe our
+ * @idle_cpus_mask store, it must observe the @has_blocked
+ * and @needs_update stores.
+ */
+ smp_mb__after_atomic();
+
+ set_cpu_sd_state_idle(cpu);
+
+ WRITE_ONCE(nohz.needs_update, 1);
+out:
+ /*
+ * Each time a cpu enter idle, we assume that it has blocked load and
+ * enable the periodic update of the load of idle CPUs
+ */
+ WRITE_ONCE(nohz.has_blocked, 1);
+}
+
+static bool update_nohz_stats(struct rq *rq)
+{
+ unsigned int cpu = rq->cpu;
+
+ if (!rq->has_blocked_load)
+ return false;
+
+ if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
+ return false;
+
+ if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick)))
+ return true;
+
+ sched_balance_update_blocked_averages(cpu);
+
+ return rq->has_blocked_load;
+}
+
+/*
+ * Internal function that runs load balance for all idle CPUs. The load balance
+ * can be a simple update of blocked load or a complete load balance with
+ * tasks movement depending of flags.
+ */
+static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags)
+{
+ /* Earliest time when we have to do rebalance again */
+ unsigned long now = jiffies;
+ unsigned long next_balance = now + 60*HZ;
+ bool has_blocked_load = false;
+ int update_next_balance = 0;
+ int this_cpu = this_rq->cpu;
+ int balance_cpu;
+ struct rq *rq;
+
+ SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
+
+ /*
+ * We assume there will be no idle load after this update and clear
+ * the has_blocked flag. If a cpu enters idle in the mean time, it will
+ * set the has_blocked flag and trigger another update of idle load.
+ * Because a cpu that becomes idle, is added to idle_cpus_mask before
+ * setting the flag, we are sure to not clear the state and not
+ * check the load of an idle cpu.
+ *
+ * Same applies to idle_cpus_mask vs needs_update.
+ */
+ if (flags & NOHZ_STATS_KICK)
+ WRITE_ONCE(nohz.has_blocked, 0);
+ if (flags & NOHZ_NEXT_KICK)
+ WRITE_ONCE(nohz.needs_update, 0);
+
+ /*
+ * Ensures that if we miss the CPU, we must see the has_blocked
+ * store from nohz_balance_enter_idle().
+ */
+ smp_mb();
+
+ /*
+ * Start with the next CPU after this_cpu so we will end with this_cpu and let a
+ * chance for other idle cpu to pull load.
+ */
+ for_each_cpu_wrap(balance_cpu, nohz.idle_cpus_mask, this_cpu+1) {
+ if (!idle_cpu(balance_cpu))
+ continue;
+
+ /*
+ * If this CPU gets work to do, stop the load balancing
+ * work being done for other CPUs. Next load
+ * balancing owner will pick it up.
+ */
+ if (need_resched()) {
+ if (flags & NOHZ_STATS_KICK)
+ has_blocked_load = true;
+ if (flags & NOHZ_NEXT_KICK)
+ WRITE_ONCE(nohz.needs_update, 1);
+ goto abort;
+ }
+
+ rq = cpu_rq(balance_cpu);
+
+ if (flags & NOHZ_STATS_KICK)
+ has_blocked_load |= update_nohz_stats(rq);
+
+ /*
+ * If time for next balance is due,
+ * do the balance.
+ */
+ if (time_after_eq(jiffies, rq->next_balance)) {
+ struct rq_flags rf;
+
+ rq_lock_irqsave(rq, &rf);
+ update_rq_clock(rq);
+ rq_unlock_irqrestore(rq, &rf);
+
+ if (flags & NOHZ_BALANCE_KICK)
+ sched_balance_domains(rq, CPU_IDLE);
+ }
+
+ if (time_after(next_balance, rq->next_balance)) {
+ next_balance = rq->next_balance;
+ update_next_balance = 1;
+ }
+ }
+
+ /*
+ * next_balance will be updated only when there is a need.
+ * When the CPU is attached to null domain for ex, it will not be
+ * updated.
+ */
+ if (likely(update_next_balance))
+ nohz.next_balance = next_balance;
+
+ if (flags & NOHZ_STATS_KICK)
+ WRITE_ONCE(nohz.next_blocked,
+ now + msecs_to_jiffies(LOAD_AVG_PERIOD));
+
+abort:
+ /* There is still blocked load, enable periodic update */
+ if (has_blocked_load)
+ WRITE_ONCE(nohz.has_blocked, 1);
+}
+
+/*
+ * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
+ * rebalancing for all the CPUs for whom scheduler ticks are stopped.
+ */
+static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
+{
+ unsigned int flags = this_rq->nohz_idle_balance;
+
+ if (!flags)
+ return false;
+
+ this_rq->nohz_idle_balance = 0;
+
+ if (idle != CPU_IDLE)
+ return false;
+
+ _nohz_idle_balance(this_rq, flags);
+
+ return true;
+}
+
+/*
+ * Check if we need to directly run the ILB for updating blocked load before
+ * entering idle state. Here we run ILB directly without issuing IPIs.
+ *
+ * Note that when this function is called, the tick may not yet be stopped on
+ * this CPU yet. nohz.idle_cpus_mask is updated only when tick is stopped and
+ * cleared on the next busy tick. In other words, nohz.idle_cpus_mask updates
+ * don't align with CPUs enter/exit idle to avoid bottlenecks due to high idle
+ * entry/exit rate (usec). So it is possible that _nohz_idle_balance() is
+ * called from this function on (this) CPU that's not yet in the mask. That's
+ * OK because the goal of nohz_run_idle_balance() is to run ILB only for
+ * updating the blocked load of already idle CPUs without waking up one of
+ * those idle CPUs and outside the preempt disable / IRQ off phase of the local
+ * cpu about to enter idle, because it can take a long time.
+ */
+void nohz_run_idle_balance(int cpu)
+{
+ unsigned int flags;
+
+ flags = atomic_fetch_andnot(NOHZ_NEWILB_KICK, nohz_flags(cpu));
+
+ /*
+ * Update the blocked load only if no SCHED_SOFTIRQ is about to happen
+ * (i.e. NOHZ_STATS_KICK set) and will do the same.
+ */
+ if ((flags == NOHZ_NEWILB_KICK) && !need_resched())
+ _nohz_idle_balance(cpu_rq(cpu), NOHZ_STATS_KICK);
+}
+
+static void nohz_newidle_balance(struct rq *this_rq)
+{
+ int this_cpu = this_rq->cpu;
+
+ /*
+ * This CPU doesn't want to be disturbed by scheduler
+ * housekeeping
+ */
+ if (!housekeeping_cpu(this_cpu, HK_TYPE_SCHED))
+ return;
+
+ /* Will wake up very soon. No time for doing anything else*/
+ if (this_rq->avg_idle < sysctl_sched_migration_cost)
+ return;
+
+ /* Don't need to update blocked load of idle CPUs*/
+ if (!READ_ONCE(nohz.has_blocked) ||
+ time_before(jiffies, READ_ONCE(nohz.next_blocked)))
+ return;
+
+ /*
+ * Set the need to trigger ILB in order to update blocked load
+ * before entering idle state.
+ */
+ atomic_or(NOHZ_NEWILB_KICK, nohz_flags(this_cpu));
+}
+
+#else /* !CONFIG_NO_HZ_COMMON */
+static inline void nohz_balancer_kick(struct rq *rq) { }
+
+static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
+{
+ return false;
+}
+
+static inline void nohz_newidle_balance(struct rq *this_rq) { }
+#endif /* CONFIG_NO_HZ_COMMON */
+
+/*
+ * sched_balance_newidle is called by schedule() if this_cpu is about to become
+ * idle. Attempts to pull tasks from other CPUs.
+ *
+ * Returns:
+ * < 0 - we released the lock and there are !fair tasks present
+ * 0 - failed, no new tasks
+ * > 0 - success, new (fair) tasks present
+ */
+int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
+{
+ unsigned long next_balance = jiffies + HZ;
+ int this_cpu = this_rq->cpu;
+ int continue_balancing = 1;
+ u64 t0, t1, curr_cost = 0;
+ struct sched_domain *sd;
+ int pulled_task = 0;
+
+ update_misfit_status(NULL, this_rq);
+
+ /*
+ * There is a task waiting to run. No need to search for one.
+ * Return 0; the task will be enqueued when switching to idle.
+ */
+ if (this_rq->ttwu_pending)
+ return 0;
+
+ /*
+ * We must set idle_stamp _before_ calling sched_balance_rq()
+ * for CPU_NEWLY_IDLE, such that we measure the this duration
+ * as idle time.
+ */
+ this_rq->idle_stamp = rq_clock(this_rq);
+
+ /*
+ * Do not pull tasks towards !active CPUs...
+ */
+ if (!cpu_active(this_cpu))
+ return 0;
+
+ /*
+ * This is OK, because current is on_cpu, which avoids it being picked
+ * for load-balance and preemption/IRQs are still disabled avoiding
+ * further scheduler activity on it and we're being very careful to
+ * re-start the picking loop.
+ */
+ rq_unpin_lock(this_rq, rf);
+
+ rcu_read_lock();
+ sd = rcu_dereference_check_sched_domain(this_rq->sd);
+
+ if (!get_rd_overloaded(this_rq->rd) ||
+ (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {
+
+ if (sd)
+ update_next_balance(sd, &next_balance);
+ rcu_read_unlock();
+
+ goto out;
+ }
+ rcu_read_unlock();
+
+ raw_spin_rq_unlock(this_rq);
+
+ t0 = sched_clock_cpu(this_cpu);
+ sched_balance_update_blocked_averages(this_cpu);
+
+ rcu_read_lock();
+ for_each_domain(this_cpu, sd) {
+ u64 domain_cost;
+
+ update_next_balance(sd, &next_balance);
+
+ if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
+ break;
+
+ if (sd->flags & SD_BALANCE_NEWIDLE) {
+
+ pulled_task = sched_balance_rq(this_cpu, this_rq,
+ sd, CPU_NEWLY_IDLE,
+ &continue_balancing);
+
+ t1 = sched_clock_cpu(this_cpu);
+ domain_cost = t1 - t0;
+ update_newidle_cost(sd, domain_cost);
+
+ curr_cost += domain_cost;
+ t0 = t1;
+ }
+
+ /*
+ * Stop searching for tasks to pull if there are
+ * now runnable tasks on this rq.
+ */
+ if (pulled_task || !continue_balancing)
+ break;
+ }
+ rcu_read_unlock();
+
+ raw_spin_rq_lock(this_rq);
+
+ if (curr_cost > this_rq->max_idle_balance_cost)
+ this_rq->max_idle_balance_cost = curr_cost;
+
+ /*
+ * While browsing the domains, we released the rq lock, a task could
+ * have been enqueued in the meantime. Since we're not going idle,
+ * pretend we pulled a task.
+ */
+ if (this_rq->cfs.h_nr_running && !pulled_task)
+ pulled_task = 1;
+
+ /* Is there a task of a high priority class? */
+ if (this_rq->nr_running != this_rq->cfs.h_nr_running)
+ pulled_task = -1;
+
+out:
+ /* Move the next balance forward */
+ if (time_after(this_rq->next_balance, next_balance))
+ this_rq->next_balance = next_balance;
+
+ if (pulled_task)
+ this_rq->idle_stamp = 0;
+ else
+ nohz_newidle_balance(this_rq);
+
+ rq_repin_lock(this_rq, rf);
+
+ return pulled_task;
+}
+
+/*
+ * This softirq handler is triggered via SCHED_SOFTIRQ from two places:
+ *
+ * - directly from the local scheduler_tick() for periodic load balancing
+ *
+ * - indirectly from a remote scheduler_tick() for NOHZ idle balancing
+ * through the SMP cross-call nohz_csd_func()
+ */
+__latent_entropy void sched_balance_softirq(struct softirq_action *h)
+{
+ struct rq *this_rq = this_rq();
+ enum cpu_idle_type idle = this_rq->idle_balance;
+ /*
+ * If this CPU has a pending NOHZ_BALANCE_KICK, then do the
+ * balancing on behalf of the other idle CPUs whose ticks are
+ * stopped. Do nohz_idle_balance *before* sched_balance_domains to
+ * give the idle CPUs a chance to load balance. Else we may
+ * load balance only within the local sched_domain hierarchy
+ * and abort nohz_idle_balance altogether if we pull some load.
+ */
+ if (nohz_idle_balance(this_rq, idle))
+ return;
+
+ /* normal load balance */
+ sched_balance_update_blocked_averages(this_rq->cpu);
+ sched_balance_domains(this_rq, idle);
+}
+
+/*
+ * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
+ */
+void sched_balance_trigger(struct rq *rq)
+{
+ /*
+ * Don't need to rebalance while attached to NULL domain or
+ * runqueue CPU is not active
+ */
+ if (unlikely(on_null_domain(rq) || !cpu_active(cpu_of(rq))))
+ return;
+
+ if (time_after_eq(jiffies, rq->next_balance))
+ raise_softirq(SCHED_SOFTIRQ);
+
+ nohz_balancer_kick(rq);
+}
+
+#endif /* CONFIG_SMP */
+
+__init void init_sched_fair_class_balance(void)
+{
+#ifdef CONFIG_SMP
+ int i;
+
+ for_each_possible_cpu(i) {
+ zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i), GFP_KERNEL, cpu_to_node(i));
+ zalloc_cpumask_var_node(&per_cpu(should_we_balance_tmpmask, i),
+ GFP_KERNEL, cpu_to_node(i));
+
+ }
+
+ open_softirq(SCHED_SOFTIRQ, sched_balance_softirq);
+
+#ifdef CONFIG_NO_HZ_COMMON
+ nohz.next_balance = jiffies;
+ nohz.next_blocked = jiffies;
+ zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
+#endif
+#endif /* SMP */
+}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 18b4c8147364..7f1d856fdc3b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2502,6 +2502,7 @@ extern void update_max_interval(void);
extern void init_sched_dl_class(void);
extern void init_sched_rt_class(void);
extern void init_sched_fair_class(void);
+extern void init_sched_fair_class_balance(void);
extern void reweight_task(struct task_struct *p, int prio);
@@ -3088,6 +3089,11 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
{
return READ_ONCE(rq->avg_rt.util_avg);
}
+
+extern unsigned long cpu_load_without(struct rq *rq, struct task_struct *p);
+extern unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p);
+extern unsigned long cpu_util_without(int cpu, struct task_struct *p);
+
#endif
#ifdef CONFIG_UCLAMP_TASK
@@ -3594,4 +3600,254 @@ static inline void balance_callbacks(struct rq *rq, struct balance_callback *hea
#endif
+#ifdef CONFIG_SMP
+int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf);
+extern struct sched_group *
+sched_balance_find_dst_group(struct sched_domain *sd, struct task_struct *p, int this_cpu);
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+extern unsigned long task_h_load(struct task_struct *p);
+#else
+static unsigned long task_h_load(struct task_struct *p)
+{
+ return p->se.avg.load_avg;
+}
+#endif
+
+#else /* !CONFIG_SMP: */
+static inline int sched_balance_newidle(struct rq *rq, struct rq_flags *rf)
+{
+ return 0;
+}
+#endif /* !CONFIG_SMP */
+
+extern __latent_entropy void sched_balance_softirq(struct softirq_action *h);
+
+#ifdef CONFIG_CFS_BANDWIDTH
+extern int throttled_lb_pair(struct task_group *tg, int src_cpu, int dest_cpu);
+#else
+static inline int throttled_lb_pair(struct task_group *tg,
+ int src_cpu, int dest_cpu)
+{
+ return 0;
+}
+#endif
+
+extern void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags);
+
+#ifdef CONFIG_SMP
+
+static inline unsigned long task_util(struct task_struct *p)
+{
+ return READ_ONCE(p->se.avg.util_avg);
+}
+
+static inline unsigned long _task_util_est(struct task_struct *p)
+{
+ return READ_ONCE(p->se.avg.util_est) & ~UTIL_AVG_UNCHANGED;
+}
+
+static inline unsigned long task_util_est(struct task_struct *p)
+{
+ return max(task_util(p), _task_util_est(p));
+}
+
+/*
+ * Optional action to be done while updating the load average
+ */
+#define UPDATE_TG 0x1
+#define SKIP_AGE_LOAD 0x2
+#define DO_ATTACH 0x4
+#define DO_DETACH 0x8
+
+extern void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags);
+
+static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
+{
+ return cfs_rq->avg.load_avg;
+}
+
+static inline unsigned long cpu_load(struct rq *rq)
+{
+ return cfs_rq_load_avg(&rq->cfs);
+}
+
+#else /* !CONFIG_SMP: */
+
+#define UPDATE_TG 0x0
+#define SKIP_AGE_LOAD 0x0
+#define DO_ATTACH 0x0
+#define DO_DETACH 0x0
+
+static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
+{
+ cfs_rq_util_change(cfs_rq, 0);
+}
+
+#endif /* !CONFIG_SMP */
+
+#ifdef CONFIG_SMP
+extern void enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se);
+extern void dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se);
+extern void check_update_overutilized_status(struct rq *rq);
+extern void util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p);
+extern void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p);
+extern void util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep);
+#else
+static inline void enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
+static inline void dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
+static inline void check_update_overutilized_status(struct rq *rq) { }
+static inline void util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
+static inline void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
+static inline void util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) {}
+#endif
+
+#ifdef CONFIG_SMP
+/*
+ * Signed add and clamp on underflow.
+ *
+ * Explicitly do a load-store to ensure the intermediate value never hits
+ * memory. This allows lockless observations without ever seeing the negative
+ * values.
+ */
+#define add_positive(_ptr, _val) do { \
+ typeof(_ptr) ptr = (_ptr); \
+ typeof(_val) val = (_val); \
+ typeof(*ptr) res, var = READ_ONCE(*ptr); \
+ \
+ res = var + val; \
+ \
+ if (val < 0 && res > var) \
+ res = 0; \
+ \
+ WRITE_ONCE(*ptr, res); \
+} while (0)
+
+/*
+ * Unsigned subtract and clamp on underflow.
+ *
+ * Explicitly do a load-store to ensure the intermediate value never hits
+ * memory. This allows lockless observations without ever seeing the negative
+ * values.
+ */
+#define sub_positive(_ptr, _val) do { \
+ typeof(_ptr) ptr = (_ptr); \
+ typeof(*ptr) val = (_val); \
+ typeof(*ptr) res, var = READ_ONCE(*ptr); \
+ res = var - val; \
+ if (res > var) \
+ res = 0; \
+ WRITE_ONCE(*ptr, res); \
+} while (0)
+
+/*
+ * Remove and clamp on negative, from a local variable.
+ *
+ * A variant of sub_positive(), which does not use explicit load-store
+ * and is thus optimized for local variable updates.
+ */
+#define lsub_positive(_ptr, _val) do { \
+ typeof(_ptr) ptr = (_ptr); \
+ *ptr -= min_t(typeof(*ptr), *ptr, _val); \
+} while (0)
+
+extern void sync_entity_load_avg(struct sched_entity *se);
+
+extern
+int util_fits_cpu(unsigned long util,
+ unsigned long uclamp_min,
+ unsigned long uclamp_max,
+ int cpu);
+
+/*
+ * overutilized value make sense only if EAS is enabled
+ */
+static inline bool is_rd_overutilized(struct root_domain *rd)
+{
+ return !sched_energy_enabled() || READ_ONCE(rd->overutilized);
+}
+
+#ifdef CONFIG_NO_HZ_COMMON
+extern void migrate_se_pelt_lag(struct sched_entity *se);
+#else
+static inline void migrate_se_pelt_lag(struct sched_entity *se) {}
+#endif
+
+extern void clear_tg_offline_cfs_rqs(struct rq *rq);
+
+DECLARE_PER_CPU(cpumask_var_t, select_rq_mask);
+
+extern void update_tg_load_avg(struct cfs_rq *cfs_rq);
+
+static inline unsigned long capacity_of(int cpu)
+{
+ return cpu_rq(cpu)->cpu_capacity;
+}
+
+extern bool is_core_idle(int cpu);
+
+extern unsigned long cpu_runnable(struct rq *rq);
+
+extern int sched_idle_cpu(int cpu);
+
+#else /* !CONFIG_SMP: */
+
+static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) { }
+
+#endif /* !CONFIG_SMP */
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+
+/* Iterate through all leaf cfs_rq's on a runqueue */
+#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
+ list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
+ leaf_cfs_rq_list)
+
+extern void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq);
+
+/* Walk up scheduling entities hierarchy */
+
+#define for_each_sched_entity(se) \
+ for (; se; se = se->parent)
+
+extern bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq);
+
+#else /* !CONFIG_FAIR_GROUP_SCHED: */
+
+#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
+ for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
+
+static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) { }
+
+#define for_each_sched_entity(se) \
+ for (; se; se = NULL)
+
+static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
+{
+ return !cfs_rq->nr_running;
+}
+
+#endif /* !CONFIG_FAIR_GROUP_SCHED */
+
+#ifdef CONFIG_NUMA
+extern long adjust_numa_imbalance(int imbalance, int dst_running, int imb_numa_nr);
+#endif
+
+#ifdef CONFIG_NUMA_BALANCING
+extern unsigned long task_weight(struct task_struct *p, int nid, int dist);
+extern unsigned long group_weight(struct task_struct *p, int nid, int dist);
+#endif
+
+#ifdef CONFIG_SMP
+extern void update_misfit_status(struct task_struct *p, struct rq *rq);
+extern void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se);
+extern void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se);
+extern void remove_entity_load_avg(struct sched_entity *se);
+#else
+static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
+static inline void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
+static inline void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
+static inline void remove_entity_load_avg(struct sched_entity *se) {}
+#endif
+
#endif /* _KERNEL_SCHED_SCHED_H */
--
2.40.1
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