linux-kernel - Re: [PATCH v6 06/11] cpufreq/schedutil: use dl utilization tracking

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAKfTPtDi9JN2gJAZ2BPqVbKwzHxop+4yev++LZsXq-igMT0Djg@mail.gmail.com>
Date:   Fri, 8 Jun 2018 15:38:46 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     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>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Quentin Perret <quentin.perret@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Claudio Scordino <claudio@...dence.eu.com>
Subject: Re: [PATCH v6 06/11] cpufreq/schedutil: use dl utilization tracking

On 8 June 2018 at 15:36, Juri Lelli <juri.lelli@...hat.com> wrote:
> On 08/06/18 14:54, Juri Lelli wrote:
>> On 08/06/18 14:48, Vincent Guittot wrote:
>> > On 8 June 2018 at 14:39, Juri Lelli <juri.lelli@...hat.com> wrote:
>> > > Hi Vincent,
>> > >
>> > > On 08/06/18 14:09, Vincent Guittot wrote:
>> > >> Now that we have both the dl class bandwidth requirement and the dl class
>> > >> utilization, we can detect when CPU is fully used so we should run at max.
>> > >> Otherwise, we keep using the dl bandwidth requirement to define the
>> > >> utilization of the CPU
>> > >>
>> > >> Cc: Ingo Molnar <mingo@...hat.com>
>> > >> Cc: Peter Zijlstra <peterz@...radead.org>
>> > >> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
>> > >> ---
>> > >
>> > > [...]
>> > >
>> > >> @@ -190,20 +192,24 @@ static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
>> > >>       if (rq->rt.rt_nr_running)
>> > >>               return sg_cpu->max;
>> > >>
>> > >> -     util = sg_cpu->util_dl;
>> > >> -     util += sg_cpu->util_cfs;
>> > >> +     util = sg_cpu->util_cfs;
>> > >>       util += sg_cpu->util_rt;
>> > >>
>> > >> +     if ((util + sg_cpu->util_dl) >= sg_cpu->max)
>> > >> +             return sg_cpu->max;
>> > >> +
>> > >
>> > > Mmm, won't we run at max (or reach max) with a, say, 100ms/500ms DL task
>> > > running alone?
>> >
>> > not for a 100ms running task. You have to run more than 320ms to reach max value
>> >
>> > 100ms/500ms will vary between 0 and 907
>>
>> OK, right, my point I guess is still that such a task will run fine at
>> ~250 and it might be save more energy by doing so?
>
> As discussed on IRC, we still endup selecting 1/5 of max freq because
> util_dl is below max.
>
> So, turning point is at ~320ms/[something_bigger], which looks a pretty
> big runtime, but I'm not sure if having that is OK. Also, it becomes
> smaller with CFS/RT background "perturbations". Mmm.
>
> BTW, adding Luca and Claudio. :)

Argh... I have added few more but forgot Luca and Claudio. I'm very sorry