linux-kernel - Re: [PATCH] cpufreq: Avoid configuring old governors as default with intel

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Date:   Fri, 23 Oct 2020 13:59:45 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Julia Lawall <julia.lawall@...ia.fr>,
        Mel Gorman <mgorman@...e.de>, Ingo Molnar <mingo@...hat.com>,
        kernel-janitors@...r.kernel.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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Gilles Muller <Gilles.Muller@...ia.fr>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Len Brown <len.brown@...el.com>
Subject: Re: [PATCH] cpufreq: Avoid configuring old governors as default with intel_pstate

On Fri, Oct 23, 2020 at 8:17 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 22-10-20, 18:23, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Subject: [PATCH] cpufreq: Avoid configuring old governors as default with intel_pstate
> >
> > Commit 33aa46f252c7 ("cpufreq: intel_pstate: Use passive mode by
> > default without HWP") was meant to cause intel_pstate without HWP
> > to be used in the passive mode with the schedutil governor on top of
> > it by default, but it missed the case in which either "ondemand" or
> > "conservative" was selected as the default governor in the existing
> > kernel config, in which case the previous old governor configuration
> > would be used, causing the default legacy governor to be used on top
> > of intel_pstate instead of schedutil.
> >
> > Address this by preventing "ondemand" and "conservative" from being
> > configured as the default cpufreq governor in the case when schedutil
> > is the default choice for the default governor setting.
> >
> > [Note that the default cpufreq governor can still be set via the
> >  kernel command line if need be and that choice is not limited,
> >  so if anyone really wants to use one of the legacy governors by
> >  default, it can be achieved this way.]
> >
> > Fixes: 33aa46f252c7 ("cpufreq: intel_pstate: Use passive mode by default without HWP")
> > Cc: 5.8+ <stable@...r.kernel.org> # 5.8+
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/cpufreq/Kconfig |    2 ++
> >  1 file changed, 2 insertions(+)
> >
> > Index: linux-pm/drivers/cpufreq/Kconfig
> > ===================================================================
> > --- linux-pm.orig/drivers/cpufreq/Kconfig
> > +++ linux-pm/drivers/cpufreq/Kconfig
> > @@ -71,6 +71,7 @@ config CPU_FREQ_DEFAULT_GOV_USERSPACE
> >
> >  config CPU_FREQ_DEFAULT_GOV_ONDEMAND
> >       bool "ondemand"
> > +     depends on !SMP || !X86_INTEL_PSTATE
> >       select CPU_FREQ_GOV_ONDEMAND
> >       select CPU_FREQ_GOV_PERFORMANCE
> >       help
> > @@ -83,6 +84,7 @@ config CPU_FREQ_DEFAULT_GOV_ONDEMAND
> >
> >  config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
> >       bool "conservative"
> > +     depends on !SMP || !X86_INTEL_PSTATE
>
> While reading this first it felt like a SMP platforms related problem
> (which I was surprised about), and then I understood what you are
> doing.
>
> I wonder if rewriting it this way makes it more readable with same
> result eventually.
>
>         depends on !(X86_INTEL_PSTATE && SMP)

Agreed, will update.

Thanks!