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

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Message-ID: <20201027114214.irsgdlfvyo46jpww@e107158-lin>
Date:   Tue, 27 Oct 2020 11:42:14 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Valentin Schneider <valentin.schneider@....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 10/27/20 11:26, Valentin Schneider wrote:
> 
> 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.

True. This effectively makes every governor a potential user space governor.

/me not sure to be happy or grumpy about it

Thanks

--
Qais Yousef