linux-kernel - Re: [PATCH v5 00/10] track CPU utilization

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Date:   Tue, 5 Jun 2018 17:03:01 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.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>
Subject: Re: [PATCH v5 00/10] track CPU utilization

On 05/06/18 16:18, Peter Zijlstra wrote:
> On Mon, Jun 04, 2018 at 08:08:58PM +0200, Vincent Guittot wrote:

[...]

> > As you mentioned, scale_rt_capacity give the remaining capacity for
> > cfs and it will behave like cfs util_avg now that it uses PELT. So as
> > long as cfs util_avg <  scale_rt_capacity(we probably need a margin)
> > we keep using dl bandwidth + cfs util_avg + rt util_avg for selecting
> > OPP because we have remaining spare capacity but if  cfs util_avg ==
> > scale_rt_capacity, we make sure to use max OPP.
> 
> Good point, when cfs-util < cfs-cap then there is idle time and the util
> number is 'right', when cfs-util == cfs-cap we're overcommitted and
> should go max.
> 
> Since the util and cap values are aligned that should track nicely.

Yeah. Makes sense to me as well. :)