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

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Message-ID: <CAKfTPtApsWeEbbV03sx8vQTGc3i+oFsAWRNsLnyHjYCSrRMqhg@mail.gmail.com>
Date:   Thu, 14 Dec 2023 12:06:23 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     catalin.marinas@....com, will@...nel.org,
        daniel.lezcano@...aro.org, mhiramat@...nel.org,
        rui.zhang@...el.com, vschneid@...hat.com, bristot@...hat.com,
        bsegall@...gle.com, dietmar.eggemann@....com,
        juri.lelli@...hat.com, peterz@...radead.org, mingo@...hat.com,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, agross@...nel.org,
        konrad.dybcio@...aro.org, andersson@...nel.org,
        viresh.kumar@...aro.org, sudeep.holla@....com, rafael@...nel.org,
        rostedt@...dmis.org, mgorman@...e.de, amit.kachhap@...il.com,
        linux-kernel@...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 10:20, Lukasz Luba <lukasz.luba@....com> wrote:
>
>
>
> On 12/12/23 14:27, Vincent Guittot wrote:
> > Provide to the scheduler a feedback about the temporary max available
> > capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
> > filtered as the pressure will happen for dozens ms or more.
> >
> > Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> > ---
> >   drivers/cpufreq/cpufreq.c | 48 +++++++++++++++++++++++++++++++++++++++
> >   include/linux/cpufreq.h   | 10 ++++++++
> >   2 files changed, 58 insertions(+)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 44db4f59c4cc..7d5f71be8d29 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -2563,6 +2563,50 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
> >   }
> >   EXPORT_SYMBOL(cpufreq_get_policy);
> >
> > +DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
> > +EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_pressure);
>
> Why do we export this variable when we have get/update functions?
> Do we expect modules would manipulate those per-cpu variables
> independently and not like we do per-cpumask in the update func.?

No, I will remove the EXPORT_PER_CPU_SYMBOL_GPL