linux-kernel - Re: [PATCH v1] Revert "cpufreq: schedutil: Move max CPU capacity to sugov

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Message-ID: <CAJZ5v0iNjPAAn0-uygpJe0ya_LW7pfF4C8OHd+8EMLg+Ws=02Q@mail.gmail.com>
Date:   Mon, 21 Nov 2022 20:18:41 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Sam Wu <wusamuel@...gle.com>
Cc:     Lukasz Luba <lukasz.luba@....com>,
        Saravana Kannan <saravanak@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        "Isaac J . Manjarres" <isaacmanjarres@...gle.com>,
        kernel-team@...roid.com,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] Revert "cpufreq: schedutil: Move max CPU capacity to sugov_policy"

On Fri, Nov 18, 2022 at 2:00 AM Sam Wu <wusamuel@...gle.com> wrote:
>
> On Wed, Nov 16, 2022 at 3:35 AM Lukasz Luba <lukasz.luba@....com> wrote:
> > Which mainline kernel version you use in pixel6?
> I am using kernel version 6.1-rc5.
> >
> > Could you elaborate a bit how is it possible?
> > Do you have the sg_policy setup properly (and at right time)?
> > Do you have the cpu capacity from arch_scale_cpu_capacity()
> > set correctly and at the right time during this cpufreq
> > governor setup?
> >
> > IIRC in Android there is a different code for setting up the
> > cpufreq sched governor clones. In mainline we don't have to do
> > those tricks, so this might be the main difference.
> This behavior is seen on the mainline kernel. There isn't any vendor code
> modifying the behavior, and the schedutil governor is being used.
> >
> > Could you trace the value that is read from
> > arch_scale_cpu_capacity() and share it with us?
> > I suspect this value changes in time in your kernel.
> There's an additional CPU capacity normalization step during
> init_cpu_capacity_callback() that does not happen until all the CPUs come
> online. However, the sugov_start() function can be called for a subset of
> CPUs before all the CPUs are brought up and before the normalization of
> the CPU capacity values, so there could be a stale value stored
> in sugov_policy.max field.

OK, the revert has been applied as 6.1-rc material, thanks!