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

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Date:   Mon, 28 May 2018 22:08:33 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Juri Lelli <juri.lelli@...hat.com>
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 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.

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?

thanks,

 - Joel