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Date: Mon, 28 May 2018 14:37:30 +0200
From: Juri Lelli <juri.lelli@redhat.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Morten Rasmussen <Morten.Rasmussen@arm.com>,
        viresh kumar <viresh.kumar@linaro.org>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Quentin Perret <quentin.perret@arm.com>
Subject: Re: [PATCH v5 08/10] cpufreq/schedutil: take into account interrupt
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On 28/05/18 14:06, Vincent Guittot wrote:
> Hi Juri,
> 
> On 28 May 2018 at 12:41, Juri Lelli <juri.lelli@redhat.com> wrote:
> > Hi Vincent,
> >
> > On 25/05/18 15:12, 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.
> >> The CPU utilization is :
> >>   irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg
> >
> > IIUC the code below you actually propose that
> >
> >  util = [(max_cap - util_irq) * util_rq] / max_cap + util_irq
> >
> > where
> >
> >  util_rq  = /Sum rq util_avg
> >  util_irq = irq util_avg
> >
> > So, which one is what you have in mind? Or am I wrong? :)
> 
> mmh ... aren't they equal  ?
> 
> util = [(max_cap - util_irq) * util_rq] / max_cap + util_irq
> util = [(max_cap/max_cap - util_irq/max_cap) * util_rq]  + util_irq
> util = [(1 - util_irq/max_cap) * util_rq]  + util_irq
> util = util_irq +  [(1 - util_irq/max_cap) * util_rq]

Ah, indeed.