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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Thu, 26 Oct 2023 17:13:31 +0200
Message-ID: <CAKfTPtBJRT56dL7+UW-viZuK3wKfGimQfrkvtuCQ_20g4N5LPQ@mail.gmail.com>
Subject: Re: [PATCH v3 3/6] cpufreq/schedutil: use a fixed reference frequency
To:     Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc:     linux@armlinux.org.uk, catalin.marinas@arm.com, will@kernel.org,
        paul.walmsley@sifive.com, palmer@dabbelt.com,
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On Wed, 25 Oct 2023 at 22:13, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:
>
> On 18/10/2023 18:25, Vincent Guittot wrote:
> > cpuinfo.max_freq can change at runtime because of boost as an example. This
> > implies that the value could be different than the one that has been
> > used when computing the capacity of a CPU.
> >
> > The new arch_scale_freq_ref() returns a fixed and coherent reference
> > frequency that can be used when computing a frequency based on utilization.
> >
> > Use this arch_scale_freq_ref() when available and fallback to
> > policy otherwise.
> >
> > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> > Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
> > Tested-by: Lukasz Luba <lukasz.luba@arm.com>
> >
> > ---
> >  kernel/sched/cpufreq_schedutil.c | 26 ++++++++++++++++++++++++--
> >  1 file changed, 24 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index 458d359f5991..6e4030482ae8 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -114,6 +114,28 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy)
> >       }
> >  }
> >
> > +/**
> > + * cpufreq_get_capacity_ref_freq - get the reference frequency of a given CPU that
>
> s/cpufreq_get_capacity_ref_freq/get_capacity_ref_freq
>
> s/of a given CPU/for a given cpufreq policy ? (of which the CPU managing
> it is used for the arch_scale_freq_ref() call in the function.
>
> > + * has been used to correlate frequency and compute capacity.
> > + * @policy: the cpufreq policy of the CPU in question.
> > + * @use_current: Fallback to current freq instead of policy->cpuinfo.max_freq.
>
> Looks like use_current does not exists as a parameter.

Thanks for the review. I'm going to apply your comments

>
> > + *
> > + * Return: the reference CPU frequency to compute a capacity.
> > + */
> > +static __always_inline
> > +unsigned long get_capacity_ref_freq(struct cpufreq_policy *policy)
> > +{
> > +     unsigned int freq = arch_scale_freq_ref(policy->cpu);
> > +
> > +     if (freq)
> > +             return freq;
> > +
> > +     if (arch_scale_freq_invariant())
> > +             return policy->cpuinfo.max_freq;
> > +
> > +     return policy->cur;
> > +}
>
> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
>
>
>