linux-kernel - Re: [PATCH v5 09/14] sched: Add over-utilization/tipping point indicator

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Message-ID: <20180806110211.kvibet576unwaowl@queper01-lin>
Date:   Mon, 6 Aug 2018 12:02:13 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
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@...cinc.com,
        "Kannan, Saravana" <skannan@...cinc.com>, 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 v5 09/14] sched: Add over-utilization/tipping point
 indicator

On Monday 06 Aug 2018 at 12:45:44 (+0200), Vincent Guittot wrote:
> On Mon, 6 Aug 2018 at 11:43, Quentin Perret <quentin.perret@....com> wrote:
> I would have preferred to have a full power policy for all task when
> EAS is in used by default and then see if there is any performance
> problem instead of letting some UC unclear but that's a personal
> opinion.

Understood. I'd say let's keep things simple for now unless there is a
consensus that this is must-have form the start.

> so IMO, the minimum is to add a comment in the code that describes
> this behavior for fork tasks so people will understand why EAS puts
> newly created task on not "EAS friendly" cpus when they will look at
> the code trying to understand the behavior

Agreed, that really needs to be documented. I'll add a comment somewhere
in v6.

Thanks,
Quentin