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

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Message-ID: <20201202165828.GC2414@hirez.programming.kicks-ass.net>
Date:   Wed, 2 Dec 2020 17:58:28 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mel Gorman <mgorman@...e.de>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        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

On Wed, Dec 02, 2020 at 04:45:31PM +0000, Mel Gorman wrote:

> > > It's less obvious what the consequence is unless the reader manages to
> > > tie the IO-wait comment in "Schedutil / DVFS" to this section.
> > 
> > I'm not entirely sure I follow. The purpose of UTIL_EST is to avoid
> > ramp-up issues and isn't related to IO-wait boosting.
> > 
> 
> I mixed up the example. Historically io-wait boosting was one way of
> avoiding DVFS ramp-up issues but now that I reread it, it's best to leave
> it general like you already have in your current version.

So IO-wait boosting is an interesting case; as it captures something not
present in the rest of the model, namely interaction.

There's also that series of patches that does the cpu/gpu interaction
thing.

It would be worth expanding on it, but I didn't have it in me to dig
through the archives to get a coherent description of the current state
of things. Something left todo later...