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Message-Id: <20230515115735.296329-2-dietmar.eggemann@arm.com>
Date: Mon, 15 May 2023 13:57:34 +0200
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>
Cc: Qais Yousef <qyousef@...alina.io>,
Kajetan Puchalski <kajetan.puchalski@....com>,
Morten Rasmussen <morten.rasmussen@....com>,
Vincent Donnefort <vdonnefort@...gle.com>,
Quentin Perret <qperret@...gle.com>,
Abhijeet Dharmapurikar <adharmap@...cinc.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/2] sched/fair: Refactor CPU utilization functions
There is a lot of code duplication in cpu_util_next() & cpu_util_cfs().
Remove this by allowing cpu_util_next() to be called with p = NULL.
Rename cpu_util_next() to cpu_util() since the '_next' suffix is no
longer necessary to distinct cpu utilization related functions.
Implement cpu_util_cfs(cpu) as cpu_util(cpu, p = NULL, -1).
This will allow to code future related cpu util changes only in one
place, namely in cpu_util().
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
---
kernel/sched/fair.c | 63 ++++++++++++++++++++++++++++++++++----------
kernel/sched/sched.h | 47 +--------------------------------
2 files changed, 50 insertions(+), 60 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3f8135d7c89d..9874e28d5e38 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7145,11 +7145,41 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
return target;
}
-/*
- * Predicts what cpu_util(@cpu) would return if @p was removed from @cpu
- * (@dst_cpu = -1) or migrated to @dst_cpu.
- */
-static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
+/**
+ * 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
+ *
+ * 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.
+ *
+ * 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: (Estimated) utilization for the specified CPU.
+ */
+static unsigned long cpu_util(int cpu, struct task_struct *p, int dst_cpu)
{
struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
unsigned long util = READ_ONCE(cfs_rq->avg.util_avg);
@@ -7160,9 +7190,9 @@ static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
* contribution. In all the other cases @cpu is not impacted by the
* migration so its util_avg is already correct.
*/
- if (task_cpu(p) == cpu && dst_cpu != cpu)
+ if (p && task_cpu(p) == cpu && dst_cpu != cpu)
lsub_positive(&util, task_util(p));
- else if (task_cpu(p) != cpu && dst_cpu == cpu)
+ else if (p && task_cpu(p) != cpu && dst_cpu == cpu)
util += task_util(p);
if (sched_feat(UTIL_EST)) {
@@ -7198,7 +7228,7 @@ static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
*/
if (dst_cpu == cpu)
util_est += _task_util_est(p);
- else if (unlikely(task_on_rq_queued(p) || current == 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);
@@ -7207,6 +7237,11 @@ static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
return min(util, capacity_orig_of(cpu));
}
+unsigned long cpu_util_cfs(int cpu)
+{
+ return cpu_util(cpu, NULL, -1);
+}
+
/*
* cpu_util_without: compute cpu utilization without any contributions from *p
* @cpu: the CPU which utilization is requested
@@ -7224,9 +7259,9 @@ 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))
- return cpu_util_cfs(cpu);
+ p = NULL;
- return cpu_util_next(cpu, p, -1);
+ return cpu_util(cpu, p, -1);
}
/*
@@ -7273,7 +7308,7 @@ static inline void eenv_task_busy_time(struct energy_env *eenv,
* cpu_capacity.
*
* The contribution of the task @p for which we want to estimate the
- * energy cost is removed (by cpu_util_next()) and must be calculated
+ * 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
@@ -7294,7 +7329,7 @@ static inline void eenv_pd_busy_time(struct energy_env *eenv,
int cpu;
for_each_cpu(cpu, pd_cpus) {
- unsigned long util = cpu_util_next(cpu, p, -1);
+ unsigned long util = cpu_util(cpu, p, -1);
busy_time += effective_cpu_util(cpu, util, ENERGY_UTIL, NULL);
}
@@ -7318,7 +7353,7 @@ eenv_pd_max_util(struct energy_env *eenv, struct cpumask *pd_cpus,
for_each_cpu(cpu, pd_cpus) {
struct task_struct *tsk = (cpu == dst_cpu) ? p : NULL;
- unsigned long util = cpu_util_next(cpu, p, dst_cpu);
+ unsigned long util = cpu_util(cpu, p, dst_cpu);
unsigned long cpu_util;
/*
@@ -7464,7 +7499,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
if (!cpumask_test_cpu(cpu, p->cpus_ptr))
continue;
- util = cpu_util_next(cpu, p, cpu);
+ util = cpu_util(cpu, p, cpu);
cpu_cap = capacity_of(cpu);
/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ec7b3e0a2b20..f78c0f85cc76 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2946,53 +2946,8 @@ static inline unsigned long cpu_util_dl(struct rq *rq)
return READ_ONCE(rq->avg_dl.util_avg);
}
-/**
- * cpu_util_cfs() - Estimates the amount of CPU capacity used by CFS tasks.
- * @cpu: the CPU to get the utilization for.
- *
- * 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.
- *
- * 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: (Estimated) utilization for the specified CPU.
- */
-static inline unsigned long cpu_util_cfs(int cpu)
-{
- struct cfs_rq *cfs_rq;
- unsigned long util;
-
- cfs_rq = &cpu_rq(cpu)->cfs;
- util = READ_ONCE(cfs_rq->avg.util_avg);
- if (sched_feat(UTIL_EST)) {
- util = max_t(unsigned long, util,
- READ_ONCE(cfs_rq->avg.util_est.enqueued));
- }
-
- return min(util, capacity_orig_of(cpu));
-}
+extern unsigned long cpu_util_cfs(int cpu);
static inline unsigned long cpu_util_rt(struct rq *rq)
{
--
2.25.1
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