linux-kernel - Re: [PATCH 1/4] cpufreq: Add a cpufreq pressure feedback for the scheduler

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Date:   Thu, 14 Dec 2023 08:57:14 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     catalin.marinas@....com, will@...nel.org, sudeep.holla@....com,
        rafael@...nel.org, agross@...nel.org, andersson@...nel.org,
        konrad.dybcio@...aro.org, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, lukasz.luba@....com,
        rui.zhang@...el.com, mhiramat@...nel.org,
        daniel.lezcano@...aro.org, amit.kachhap@...il.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] cpufreq: Add a cpufreq pressure feedback for the scheduler

On Thu, 14 Dec 2023 at 06:43, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 12-12-23, 15:27, Vincent Guittot wrote:
> > @@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> >       policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
> >       trace_cpu_frequency_limits(policy);
> >
> > +     cpus = policy->related_cpus;
> > +     cpufreq_update_pressure(cpus, policy->max);
> > +
> >       policy->cached_target_freq = UINT_MAX;
>
> One more question, why are you doing this from cpufreq_set_policy ? If
> due to cpufreq cooling or from userspace, we end up limiting the
> maximum possible frequency, will this routine always get called ?

Yes, any update of a FREQ_QOS_MAX ends up calling cpufreq_set_policy()
to update the policy->max


>
> --
> viresh