linux-kernel - Re: [PATCH v5 08/10] cpufreq/schedutil: take into account interrupt

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Date:   Mon, 28 May 2018 14:06:02 +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>,
        Quentin Perret <quentin.perret@....com>
Subject: Re: [PATCH v5 08/10] cpufreq/schedutil: take into account interrupt

Hi Juri,

On 28 May 2018 at 12:41, Juri Lelli <juri.lelli@...hat.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]

>
> [...]
>
>>  static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
>> @@ -190,9 +192,17 @@ static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
>>       if (rq->rt.rt_nr_running) {
>>               util = sg_cpu->max;
>>       } else {
>> +             /* Sum rq utilization*/
>>               util = sg_cpu->util_dl;
>>               util += sg_cpu->util_cfs;
>>               util += sg_cpu->util_rt;
>> +
>> +             /* Weight rq's utilization to the normal context */
>> +             util *= (sg_cpu->max - sg_cpu->util_irq);
>> +             util /= sg_cpu->max;
>> +
>> +             /* Add interrupt utilization */
>> +             util += sg_cpu->util_irq;
>
> Thanks,
>
> - Juri