From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick Bellasi Subject: [PATCH 2/3] sched/fair: util_est: update before schedutil Date: Thu, 10 May 2018 16:05:52 +0100 Message-ID: <20180510150553.28122-3-patrick.bellasi@arm.com> References: <20180510150553.28122-1-patrick.bellasi@arm.com> Return-path: In-Reply-To: <20180510150553.28122-1-patrick.bellasi@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Joel Fernandes , Steve Muckle List-Id: linux-pm@vger.kernel.org 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 Signed-off-by: Patrick Bellasi Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Vincent Guittot 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