linux-kernel - Re: [PATCH] cpufreq: Change default transition delay to 2ms

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Date: Mon, 12 Feb 2024 16:53:14 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Viresh Kumar <viresh.kumar@...aro.org>, Qais Yousef <qyousef@...alina.io>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-pm@...r.kernel.org, Ingo Molnar <mingo@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH] cpufreq: Change default transition delay to 2ms

On Mon, Feb 5, 2024 at 8:45 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 05-02-24, 02:25, Qais Yousef wrote:
> > 10ms is too high for today's hardware, even low end ones. This default
> > end up being used a lot on Arm machines at least. Pine64, mac mini and
> > pixel 6 all end up with 10ms rate_limit_us when using schedutil, and
> > it's too high for all of them.
> >
> > Change the default to 2ms which should be 'pessimistic' enough for worst
> > case scenario, but not too high for platforms with fast DVFS hardware.
> >
> > Signed-off-by: Qais Yousef <qyousef@...alina.io>
> > ---
> >  drivers/cpufreq/cpufreq.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 44db4f59c4cc..8207f7294cb6 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -582,11 +582,11 @@ unsigned int cpufreq_policy_transition_delay_us(struct cpufreq_policy *policy)
> >                * for platforms where transition_latency is in milliseconds, it
> >                * ends up giving unrealistic values.
> >                *
> > -              * Cap the default transition delay to 10 ms, which seems to be
> > +              * Cap the default transition delay to 2 ms, which seems to be
> >                * a reasonable amount of time after which we should reevaluate
> >                * the frequency.
> >                */
> > -             return min(latency * LATENCY_MULTIPLIER, (unsigned int)10000);
> > +             return min(latency * LATENCY_MULTIPLIER, (unsigned int)(2*MSEC_PER_SEC));
>
> Please add spaces around '*'.
>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

I've adjusted the whitespace as suggested above and applied the patch
as 5.9 material.

Thanks!