linux-kernel - Re: [PATCH v5 05/10] cpufreq/schedutil: get max utilization

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Date:   Tue, 29 May 2018 08:31:58 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>, peterz@...radead.org,
        mingo@...nel.org, linux-kernel@...r.kernel.org, rjw@...ysocki.net,
        dietmar.eggemann@....com, Morten.Rasmussen@....com,
        viresh.kumar@...aro.org, valentin.schneider@....com,
        quentin.perret@....com, Luca Abeni <luca.abeni@...tannapisa.it>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Alessio Balsini <alessio.balsini@...tannapisa.it>
Subject: Re: [PATCH v5 05/10] cpufreq/schedutil: get max utilization

On 28/05/18 22:08, Joel Fernandes wrote:
> On Mon, May 28, 2018 at 12:12:34PM +0200, Juri Lelli wrote:
> [..] 
> > > +
> > > +	util = max_t(unsigned long, util, READ_ONCE(rq->avg_dl.util_avg));
> > > +
> > > +	return util;
> > 
> > Anyway, just a quick thought. I guess we should experiment with this a
> > bit. Now, I don't unfortunately have a Arm platform at hand for testing.
> > Claudio, Luca (now Cc-ed), would you be able to fire some tests with
> > this change?
> > 
> > Oh, adding Joel and Alessio as well that experimented with DEADLINE
> > lately.
> 
> I also feel that for power reasons, dl.util_avg shouldn't drive the OPP
> beyond what the running bandwidth is, or atleast do that only if CFS tasks
> are running and being preempted as you/Vincent mentioned in one of the
> threads.

It's however a bit awkward that we might be running at a higher OPP when
CFS tasks are running (even though they are of less priority). :/

> With our DL experiments, I didn't measure power but got it to a point where
> the OPP is scaling correctly based on DL parameters. I think Alessio did
> measure power at his setup but I can't recall now. Alessio?

I see. Thanks.