linux-kernel - Re: [PATCH] sched/fair: schedutil: update only with all info available

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Message-ID: <20180411092756.GK14248@e110439-lin>
Date:   Wed, 11 Apr 2018 10:27:56 +0100
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>
Subject: Re: [PATCH] sched/fair: schedutil: update only with all info
 available

On 11-Apr 09:57, Vincent Guittot wrote:
> On 6 April 2018 at 19:28, Patrick Bellasi <patrick.bellasi@....com> wrote:
> 
> >  }
> > @@ -5454,8 +5441,11 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
> >                 update_cfs_group(se);
> >         }
> >
> > -       if (!se)
> > +       /* The task is no more visible from the root cfs_rq */
> > +       if (!se) {
> >                 sub_nr_running(rq, 1);
> > +               cpufreq_update_util(rq, 0);
> 
> call to cpufreq_update_util() should be done after util_est_dequeue()

Yeah... good point, looks like I should have notice it :)

That's another compelling example why updating schedutil as a side
effect of update_load_avg does not allow to easily track when it's the
best time to trigger an update.

UtilEst is now a factor which could impact on OPP selection for CFS
tasks, and thus we should update at the really end of the function.

> > +       }
> >
> >         util_est_dequeue(&rq->cfs, p, task_sleep);
> >         hrtick_update(rq);

-- 
#include <best/regards.h>

Patrick Bellasi