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Message-Id: <1415260327-30465-5-git-send-email-pang.xunlei@linaro.org>
Date: Thu, 6 Nov 2014 15:52:05 +0800
From: "pang.xunlei" <pang.xunlei@...aro.org>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Juri Lelli <juri.lelli@...il.com>,
"pang.xunlei" <pang.xunlei@...aro.org>
Subject: [PATCH v4 5/7] sched/deadline: Fix several problems with cpudl_find()
cpudl_find() has some problems:
1)in check_preempt_equal_dl(), called with NULL later_mask, thus
cpudl_find() doesn't check cpudl.free_cpus at all.
2)Also, the whole system isn't always overloaded with many DL tasks
in which cases all the cpu may have a DL task running, so it may
return the best cpu, because we only return the first maximum deadline
cpu(is there a need to iterate the same deadline value to find more
different cpus if possible?).
So it may be reasonable to change the return value of cpudl_find()
to a bool type, because it isn't always the best cpu actually which
can be better determined in find_later_rq() via sched_domain topology.
This patch adds a new cpudl_set_freecpu() to initialize cpudl.free_cpus
when rq_attach_root(), and modifies cpudl_find() and all its call sites
in order to address these problems.
Signed-off-by: pang.xunlei <pang.xunlei@...aro.org>
---
kernel/sched/core.c | 2 ++
kernel/sched/cpudeadline.c | 41 ++++++++++++++++++++++-------------------
kernel/sched/cpudeadline.h | 1 +
kernel/sched/deadline.c | 32 +++++++++++++++-----------------
4 files changed, 40 insertions(+), 36 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 240157c..17d5778 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5584,6 +5584,8 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd)
rq->rd = rd;
cpumask_set_cpu(rq->cpu, rd->span);
+ cpudl_set_freecpu(rq->cpu, &rd->cpudl);
+
if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
set_rq_online(rq);
diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 539ca3c..1dd446a 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -97,30 +97,25 @@ static inline int cpudl_maximum(struct cpudl *cp)
* cpudl_find - find the best (later-dl) CPU in the system
* @cp: the cpudl max-heap context
* @p: the task
- * @later_mask: a mask to fill in with the selected CPUs (or NULL)
+ * @later_mask: a mask to fill in with the selected CPUs (not NULL)
*
- * Returns: int - best CPU (heap maximum if suitable)
+ * Returns: (int)bool - CPUs were found
*/
int cpudl_find(struct cpudl *cp, struct task_struct *p,
struct cpumask *later_mask)
{
- int best_cpu = -1;
const struct sched_dl_entity *dl_se = &p->dl;
- if (later_mask && cpumask_and(later_mask, later_mask, cp->free_cpus)) {
- best_cpu = cpumask_any(later_mask);
- goto out;
- } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
- dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
- best_cpu = cpudl_maximum(cp);
- if (later_mask)
- cpumask_set_cpu(best_cpu, later_mask);
+ cpumask_and(later_mask, cpu_active_mask, &p->cpus_allowed);
+ if (cpumask_and(later_mask, later_mask, cp->free_cpus)) {
+ return 1;
+ } else if (cpumask_and(later_mask, cpumask_of(cpudl_maximum(cp)),
+ &p->cpus_allowed) &&
+ dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
+ return 1;
}
-out:
- WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
-
- return best_cpu;
+ return 0;
}
/*
@@ -165,7 +160,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
old_idx = parent(old_idx);
}
cpumask_set_cpu(cpu, cp->free_cpus);
- cpudl_heapify(cp, old_idx);
+ cpudl_heapify(cp, old_idx);
goto out;
}
@@ -186,6 +181,16 @@ out:
}
/*
+ * cpudl_set_freecpu - Set the cpudl.free_cpus
+ * @cpu: rd attached cpu
+ * @cp: the cpudl max-heap context
+ */
+void cpudl_set_freecpu(int cpu, struct cpudl *cp)
+{
+ cpumask_set_cpu(cpu, cp->free_cpus);
+}
+
+/*
* cpudl_init - initialize the cpudl structure
* @cp: the cpudl max-heap context
*/
@@ -203,7 +208,7 @@ int cpudl_init(struct cpudl *cp)
if (!cp->elements)
return -ENOMEM;
- if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
+ if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
kfree(cp->elements);
return -ENOMEM;
}
@@ -211,8 +216,6 @@ int cpudl_init(struct cpudl *cp)
for_each_possible_cpu(i)
cp->elements[i].idx = IDX_INVALID;
- cpumask_setall(cp->free_cpus);
-
return 0;
}
diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h
index 020039b..71478fc 100644
--- a/kernel/sched/cpudeadline.h
+++ b/kernel/sched/cpudeadline.h
@@ -25,6 +25,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid);
int cpudl_init(struct cpudl *cp);
void cpudl_cleanup(struct cpudl *cp);
+void cpudl_set_freecpu(int cpu, struct cpudl *cp);
#endif /* CONFIG_SMP */
#endif /* _LINUX_CPUDL_H */
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 5285332..e0e8013 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -965,14 +965,18 @@ out:
return cpu;
}
+static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
+
static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
{
+ struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
+
/*
* Current can't be migrated, useless to reschedule,
* let's hope p can move out.
*/
if (rq->curr->nr_cpus_allowed == 1 ||
- cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
+ !cpudl_find(&rq->rd->cpudl, rq->curr, later_mask))
return;
/*
@@ -980,7 +984,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
* see if it is pushed or pulled somewhere else.
*/
if (p->nr_cpus_allowed != 1 &&
- cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
+ cpudl_find(&rq->rd->cpudl, p, later_mask))
return;
resched_curr(rq);
@@ -1167,14 +1171,12 @@ next_node:
return NULL;
}
-static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
-
static int find_later_rq(struct task_struct *task)
{
struct sched_domain *sd;
struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
int this_cpu = smp_processor_id();
- int best_cpu, cpu = task_cpu(task);
+ int cpu = task_cpu(task);
/* Make sure the mask is initialized first */
if (unlikely(!later_mask))
@@ -1187,14 +1189,12 @@ static int find_later_rq(struct task_struct *task)
* We have to consider system topology and task affinity
* first, then we can look for a suitable cpu.
*/
- cpumask_copy(later_mask, task_rq(task)->rd->span);
- cpumask_and(later_mask, later_mask, cpu_active_mask);
- cpumask_and(later_mask, later_mask, &task->cpus_allowed);
- best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
- task, later_mask);
- if (best_cpu == -1)
+ if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask))
return -1;
+ if (cpumask_weight(later_mask) == 1)
+ return cpumask_any(later_mask);
+
/*
* If we are here, some target has been found,
* the most suitable of which is cached in best_cpu.
@@ -1219,6 +1219,7 @@ static int find_later_rq(struct task_struct *task)
rcu_read_lock();
for_each_domain(cpu, sd) {
+ int best_cpu;
if (sd->flags & SD_WAKE_AFFINE) {
/*
@@ -1231,12 +1232,9 @@ static int find_later_rq(struct task_struct *task)
return this_cpu;
}
- /*
- * Last chance: if best_cpu is valid and is
- * in the mask, that becomes our choice.
- */
- if (best_cpu < nr_cpu_ids &&
- cpumask_test_cpu(best_cpu, sched_domain_span(sd))) {
+ best_cpu = cpumask_first_and(later_mask,
+ sched_domain_span(sd));
+ if (best_cpu < nr_cpu_ids) {
rcu_read_unlock();
return best_cpu;
}
--
1.7.9.5
--
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