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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: 7f65ea42eb ("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>
This commit is contained in:
Patrick Bellasi 2018-05-24 15:10:23 +01:00 committed by Ingo Molnar
parent 8ecf04e112
commit 2539fc82aa
1 changed files with 8 additions and 1 deletions
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9
kernel/sched/fair.c
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@ -5385,6 +5385,14 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
struct cfs_rq *cfs_rq;
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
@ -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);
}