linux-kernel - Re: default cpufreq gov, was: [PATCH] sched/fair: check for idle core

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Message-ID: <jhjlffrq58y.mognet@arm.com>
Date:   Tue, 27 Oct 2020 11:26:37 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Qais Yousef <qais.yousef@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.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@...r.kernel.org,
        Gilles Muller <Gilles.Muller@...ia.fr>,
        srinivas.pandruvada@...ux.intel.com
Subject: Re: default cpufreq gov, was: [PATCH] sched/fair: check for idle core


On 27/10/20 11:11, Qais Yousef wrote:
> On 10/22/20 14:02, Peter Zijlstra wrote:
>> However I do want to retire ondemand, conservative and also very much
>> intel_pstate/active mode. I also have very little sympathy for
>> userspace.
>
> Userspace is useful for testing and sanity checking. Not sure if people use it
> to measure voltage/current at each frequency to generate
> dynamic-power-coefficient for their platform. Lukasz, Dietmar?
>

It's valuable even just for cpufreq sanity checking - we have that test
that goes through increasing frequencies and asserts the work done is
monotonically increasing. This has been quite useful in the past to detect
broken bits.

That *should* still be totally doable with any other governor by using the
scaling_{min, max}_freq sysfs interface.

> Thanks