linux-kernel - Re: [PATCH 07/11] cpufreq/schedutil: take into account interrupt

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Date:   Fri, 6 Jul 2018 11:21:50 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     viresh kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        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>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 07/11] cpufreq/schedutil: take into account interrupt

On Fri, 6 Jul 2018 at 11:14, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Fri, Jul 06, 2018 at 11:30:33AM +0530, Viresh Kumar wrote:
> > On 28-06-18, 17:45, Vincent Guittot wrote:
> > > The time spent under interrupt can be significant but it is not reflected
> > > in the utilization of CPU when deciding to choose an OPP. Now that we have
> > > access to this metric, schedutil can take it into account when selecting
> > > the OPP for a CPU.
> > > rqs utilization don't see the time spend under interrupt context and report
> > > their value in the normal context time window. We need to compensate this when
> > > adding interrupt utilization
> > >
> > > The CPU utilization is :
> > >   irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg
> > >
> > > A test with iperf on hikey (octo arm64) gives:
> > > iperf -c server_address -r -t 5
> > >
> > > w/o patch           w/ patch
> > > Tx 276 Mbits/sec        304 Mbits/sec +10%
> > > Rx 299 Mbits/sec        328 Mbits/sec +09%
> > >
> > > 8 iterations
> > > stdev is lower than 1%
> > > Only WFI idle state is enable (shallowest diel state)
>
> Also s/diel/idle/
>
> > > +   /*
> > > +    * Interrupt time is not seen by rqs utilization nso we can compare
> >
> >                                                          nso ?
> >
> > > +    * them with the CPU capacity
> > > +    */
>
> Already fixed ;-)

Thanks