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authorPatrick Bellasi <patrick.bellasi@arm.com>2018-05-24 15:10:23 +0100
committerIngo Molnar <mingo@kernel.org>2018-05-25 08:04:56 +0200
commit2539fc82aa9b07d968cf9ba1ffeec3e0416ac721 (patch)
tree255d1eb5d74eb49b11d4abfea24fe17d79a968fb /kernel
parent8ecf04e11283a28ca88b8b8049ac93c3a99fcd2c (diff)
downloadlinux-2539fc82aa9b07d968cf9ba1ffeec3e0416ac721.tar.bz2
sched/fair: Update util_est before updating schedutil
When a task is enqueued the estimated utilization of a CPU is updated to better support the selection of the required frequency. However, schedutil is (implicitly) updated by update_load_avg() which always happens before util_est_{en,de}queue(), thus potentially introducing a latency between estimated utilization updates and frequency selections. Let's update util_est at the beginning of enqueue_task_fair(), which will ensure that all schedutil updates will see the most updated estimated utilization value for a CPU. Reported-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Joel Fernandes <joelaf@google.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com> Cc: Steve Muckle <smuckle@google.com> Fixes: 7f65ea42eb00 ("sched/fair: Add util_est on top of PELT") Link: http://lkml.kernel.org/r/20180524141023.13765-3-patrick.bellasi@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/fair.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 748cb054fefd..e497c05aab7f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5386,6 +5386,14 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
struct sched_entity *se = &p->se;
/*
+ * 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.
@@ -5426,7 +5434,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
if (!se)
add_nr_running(rq, 1);
- util_est_enqueue(&rq->cfs, p);
hrtick_update(rq);
}