Messages in this thread Patch in this message | | | From | Patrick Bellasi <> | Subject | [PATCH 2/3] sched/fair: util_est: update before schedutil | Date | Thu, 10 May 2018 16:05:52 +0100 |
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When a task is enqueue 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> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org --- kernel/sched/fair.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1f6a23a5b451..01dfc47541e6 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5356,6 +5356,9 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se; + /* Estimated utilization must be updated before 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 @@ -5397,7 +5400,6 @@ 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); } -- 2.15.1
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