linux-kernel - Re: [patch 06/10] x86/aperfmperf: Restructure arch_scale_freq

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Date:   Tue, 19 Apr 2022 18:20:14 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [patch 06/10] x86/aperfmperf: Restructure arch_scale_freq_tick()

On Fri, Apr 15, 2022 at 9:20 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Preparation for sharing code with the CPU frequency portion of the
> aperf/mperf code.
>
> No functional change.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

All good AFAICS:

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
>  arch/x86/kernel/cpu/aperfmperf.c |   36 +++++++++++++++++++++---------------
>  1 file changed, 21 insertions(+), 15 deletions(-)
>
> --- a/arch/x86/kernel/cpu/aperfmperf.c
> +++ b/arch/x86/kernel/cpu/aperfmperf.c
> @@ -477,22 +477,9 @@ static DECLARE_WORK(disable_freq_invaria
>
>  DEFINE_PER_CPU(unsigned long, arch_freq_scale) = SCHED_CAPACITY_SCALE;
>
> -void arch_scale_freq_tick(void)
> +static void scale_freq_tick(u64 acnt, u64 mcnt)
>  {
> -       struct aperfmperf *s = this_cpu_ptr(&cpu_samples);
> -       u64 aperf, mperf, acnt, mcnt, freq_scale;
> -
> -       if (!arch_scale_freq_invariant())
> -               return;
> -
> -       rdmsrl(MSR_IA32_APERF, aperf);
> -       rdmsrl(MSR_IA32_MPERF, mperf);
> -
> -       acnt = aperf - s->aperf;
> -       mcnt = mperf - s->mperf;
> -
> -       s->aperf = aperf;
> -       s->mperf = mperf;
> +       u64 freq_scale;
>
>         if (check_shl_overflow(acnt, 2*SCHED_CAPACITY_SHIFT, &acnt))
>                 goto error;
> @@ -514,4 +501,23 @@ void arch_scale_freq_tick(void)
>         pr_warn("Scheduler frequency invariance went wobbly, disabling!\n");
>         schedule_work(&disable_freq_invariance_work);
>  }
> +
> +void arch_scale_freq_tick(void)
> +{
> +       struct aperfmperf *s = this_cpu_ptr(&cpu_samples);
> +       u64 acnt, mcnt, aperf, mperf;
> +
> +       if (!arch_scale_freq_invariant())
> +               return;
> +
> +       rdmsrl(MSR_IA32_APERF, aperf);
> +       rdmsrl(MSR_IA32_MPERF, mperf);
> +       acnt = aperf - s->aperf;
> +       mcnt = mperf - s->mperf;
> +
> +       s->aperf = aperf;
> +       s->mperf = mperf;
> +
> +       scale_freq_tick(acnt, mcnt);
> +}
>  #endif /* CONFIG_X86_64 && CONFIG_SMP */
>