linux-kernel - Re: [PATCH 1/3] sched/cpufreq: always consider blocked FAIR utilization

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Date:   Mon, 14 May 2018 11:18:49 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        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>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>
Subject: Re: [PATCH 1/3] sched/cpufreq: always consider blocked FAIR utilization

On 11 May 2018 at 11:12, Patrick Bellasi <patrick.bellasi@....com> wrote:

>>
>> Do we need a Fixes tag and Cc stable ?
>
> Mmm... no sure, I would say that's not a fix.
>
> As I say in the changelog above, 8f111bc357aa was doing the correct
> thing but, since the recent Vincent's commit 31e77c93e432, this is an
> update worth to have, since now we can trust the decay of blocked
> utilization.
>
> Regarding stable, well... if Vincent patches are not going to be
> considered for stable, then we should not consider this too, do we?

commit 31e77c93e432 is not for stable so this patch should not go too

>
>> >
>> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
>> > index d2c6083304b4..a74d05160e66 100644
>> > --- a/kernel/sched/cpufreq_schedutil.c
>> > +++ b/kernel/sched/cpufreq_schedutil.c
>> > @@ -183,22 +183,21 @@ static void sugov_get_util(struct sugov_cpu *sg_cpu)
>> >  static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
>> >  {
>> >     struct rq *rq = cpu_rq(sg_cpu->cpu);
>> > -   unsigned long util;
>> >
>> > -   if (rq->rt.rt_nr_running) {
>> > -           util = sg_cpu->max;
>> > -   } else {
>> > -           util = sg_cpu->util_dl;
>> > -           if (rq->cfs.h_nr_running)
>> > -                   util += sg_cpu->util_cfs;
>> > -   }
>> > +   if (rq->rt.rt_nr_running)
>> > +           return sg_cpu->max;
>> >
>> >     /*
>> > +    * Utilization required by DEADLINE must always be granted while, for
>> > +    * FAIR, we use blocked utilization of IDLE CPUs as a mechanism to
>> > +    * gracefully reduce the frequency when no tasks show up for longer
>> > +    * periods of time.
>> > +    *
>> >      * Ideally we would like to set util_dl as min/guaranteed freq and
>> >      * util_cfs + util_dl as requested freq. However, cpufreq is not yet
>> >      * ready for such an interface. So, we only do the latter for now.
>> >      */
>> > -   return min(util, sg_cpu->max);
>> > +   return min(sg_cpu->max, (sg_cpu->util_dl + sg_cpu->util_cfs));
>> >  }
>> >
>> >  static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time, unsigned int flags)
>>
>> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
>>
>> --
>> viresh
>
> --
> #include <best/regards.h>
>
> Patrick Bellasi