linux-kernel - Re: [PATCH v7 02/14] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling

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Date:   Wed, 12 Sep 2018 16:56:31 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Chris Redpath <chris.redpath@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        viresh kumar <viresh.kumar@...aro.org>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        "Cc: Steve Muckle" <smuckle@...gle.com>, adharmap@...eaurora.org,
        Saravana Kannan <skannan@...eaurora.org>,
        pkondeti@...eaurora.org, Juri Lelli <juri.lelli@...hat.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        currojerez@...eup.net, Javi Merino <javi.merino@...nel.org>
Subject: Re: [PATCH v7 02/14] sched/cpufreq: Prepare schedutil for Energy
 Aware Scheduling

Hi Quentin,

On Wed, 12 Sep 2018 at 11:13, Quentin Perret <quentin.perret@....com> wrote:
>
> Schedutil requests frequency by aggregating utilization signals from
> the scheduler (CFS, RT, DL, IRQ) and applying and 25% margin on top of

quite a minor thing but s/and 25%/a 25%/

> them. Since Energy Aware Scheduling (EAS) needs to be able to predict
> the frequency requests, it needs to forecast the decisions made by the
> governor.
>
> In order to prepare the introduction of EAS, introduce
> schedutil_freq_util() to centralize the aforementioned signal
> aggregation and make it available to both schedutil and EAS. Since
> frequency selection and energy estimation still need to deal with RT and
> DL signals slightly differently, schedutil_freq_util() is called with a
> different 'type' parameter in those two contexts, and returns an
> aggregated utilization signal accordingly. While at it, introduce the
> map_util_freq() function which is designed to make schedutil's 25%
> margin usable easily for both sugov and EAS.
>
> As EAS will be able to predict schedutil's frequency requests more
> accurately than any other governor by design, it'd be sensible to make
> sure EAS cannot be used without schedutil. This will be done later, once
> EAS has actually been introduced.
>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Quentin Perret <quentin.perret@....com>