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

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Date:   Mon, 4 Jun 2018 09:04:38 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Joel Fernandes <joelaf@...gle.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        viresh kumar <viresh.kumar@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Quentin Perret <quentin.perret@....com>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>,
        Alessio Balsini <alessio.balsini@...tannapisa.it>
Subject: Re: [PATCH v5 05/10] cpufreq/schedutil: get max utilization

Hi Vincent,

On 04/06/18 08:41, Vincent Guittot wrote:
> On 1 June 2018 at 19:45, Joel Fernandes <joelaf@...gle.com> wrote:
> > On Fri, Jun 01, 2018 at 03:53:07PM +0200, Vincent Guittot wrote:

[...]

> > IMO I feel its overkill to account dl_avg when we already have DL's running
> > bandwidth we can use. I understand it may be too instanenous, but perhaps we
> 
> We keep using dl bandwidth which is quite correct for dl needs but
> doesn't reflect how it has disturbed other classes
> 
> > can fix CFS's problems within CFS itself and not have to do this kind of
> > extra external accounting ?

I would also keep accounting for waiting time due to higher prio classes
all inside CFS. My impression, when discussing it with you on IRC, was
that we should be able to do that by not decaying cfs.util_avg when CFS
is preempted (creating a new signal for it). Is not this enough?

I feel we should try to keep cross-class accounting/interaction at a
minimum.

Thanks,

- Juri