linux-kernel - Re: [RFC] Documentation/scheduler/schedutil.txt

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Message-ID: <20201120143715.GA3456@e123083-lin>
Date:   Fri, 20 Nov 2020 15:37:55 +0100
From:   Morten Rasmussen <morten.rasmussen@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        dietmar.eggemann@....com, patrick.bellasi@...bug.net,
        lenb@...nel.org, linux-kernel@...r.kernel.org,
        valentin.schneider@....com, ionela.voinescu@....com,
        qperret@...gle.com, viresh.kumar@...aro.org
Subject: Re: [RFC] Documentation/scheduler/schedutil.txt

Hi Peter,

Looks like a nice summary to me.

On Fri, Nov 20, 2020 at 08:55:27AM +0100, Peter Zijlstra wrote:
> Hi,
> 
> I was recently asked to explain how schedutil works, the below write-up
> is the result of that and I figured we might as well stick it in the
> tree.
> 
> Not as a patch for easy reading and commenting.
> 
> ---
> 
> NOTE; all this assumes a linear relation between frequency and work capacity,
> we know this is flawed, but it is the best workable approximation.

If you replace frequency with performance level everywhere (CPPC style),
most of it should still work without that assumption. The assumption
might have be made in hw or fw instead though.

Morten