Messages in this thread Patch in this message | | | From | Patrick Bellasi <> | Subject | [PATCH v3 2/2] sched/fair: util_est: update before schedutil | Date | Thu, 24 May 2018 15:10:23 +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> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> 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 Fixes: 7f65ea42eb00 ("sched/fair: Add util_est on top of PELT")
--- Changes in v3: - add "Acked-by" Vincent tags
Changes in v2: - improve comment in enqueue_task_fair() (Peter) - add "Fixes" tag - add "Acked-by" Viresh tag --- kernel/sched/fair.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
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 @@ -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); } -- 2.15.1
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