linux-kernel - Re: [PATCH v2 2/6] cpufreq: schedutil: reset sg

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Date:   Fri, 7 Jul 2017 11:17:04 +0100
From:   Juri Lelli <juri.lelli@....com>
To:     Joel Fernandes <joelaf@...gle.com>
Cc:     Patrick Bellasi <patrick.bellasi@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <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>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Andres Oportus <andresoportus@...gle.com>,
        Todd Kjos <tkjos@...roid.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v2 2/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE
 enter

On 06/07/17 21:43, Joel Fernandes wrote:
> On Tue, Jul 4, 2017 at 10:34 AM, Patrick Bellasi
> <patrick.bellasi@....com> wrote:

[...]

> > @@ -304,6 +304,12 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> >
> >         sg_cpu->util = util;
> >         sg_cpu->max = max;
> > +
> > +       /* CPU is entering IDLE, reset flags without triggering an update */
> > +       if (unlikely(flags & SCHED_CPUFREQ_IDLE)) {
> > +               sg_cpu->flags = 0;
> > +               goto done;
> > +       }
> 
> Instead of defining a new flag for idle, wouldn't another way be to
> just clear the flag from the RT scheduling class with an extra call to
> cpufreq_update_util with flags = 0 during dequeue_rt_entity? That
> seems to me to be also the right place to clear the flag since the
> flag is set in the corresponding class to begin with.
> 

Make sense to me too. Also considering that for DL (with my patches) we
don't generally want to clear the flag at dequeue time, but only when
the 0-lag timer fires.

Best,

- Juri