linux-kernel - Re: [PATCH v10 10/15] sched: Introduce a sysctl for Energy Aware Scheduling

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Date:   Tue, 11 Dec 2018 15:15:09 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     peterz@...radead.org, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        gregkh@...uxfoundation.org, mingo@...hat.com,
        dietmar.eggemann@....com, morten.rasmussen@....com,
        chris.redpath@....com, patrick.bellasi@....com,
        valentin.schneider@....com, vincent.guittot@...aro.org,
        thara.gopinath@...aro.org, viresh.kumar@...aro.org,
        tkjos@...gle.com, joel@...lfernandes.org, smuckle@...gle.com,
        adharmap@...eaurora.org, skannan@...eaurora.org,
        pkondeti@...eaurora.org, juri.lelli@...hat.com,
        edubezval@...il.com, srinivas.pandruvada@...ux.intel.com,
        currojerez@...eup.net, javi.merino@...nel.org,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH v10 10/15] sched: Introduce a sysctl for Energy Aware
 Scheduling


* Quentin Perret <quentin.perret@....com> wrote:

> In its current state, Energy Aware Scheduling (EAS) starts automatically
> on asymmetric platforms having an Energy Model (EM). However, there are
> users who want to have an EM (for thermal management for example), but
> don't want EAS with it.

Well, then introduce a new Kconfig variant for EAS, if it's super 
important to allow this to be disabled.

Why do we want to disable it - is it not reliable in some circumstances?

> In order to let users disable EAS explicitly, introduce a new sysctl
> called 'sched_energy_aware'. It is enabled by default so that EAS can
> start automatically on platforms where it makes sense. Flipping it to 0
> rebuilds the scheduling domains and disables EAS.

Yeah, making this a sysctl ABI is asking for trouble - this really should 
be a Kconfig or debug space knob, at most.

Thanks,

	Ingo