linux-kernel - Re: [PATCH 03/11] cpufreq/schedutil: use rt utilization tracking

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Date:   Fri, 6 Jul 2018 11:26:46 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, rjw@...ysocki.net,
        juri.lelli@...hat.com, dietmar.eggemann@....com,
        Morten.Rasmussen@....com, valentin.schneider@....com,
        patrick.bellasi@....com, joel@...lfernandes.org,
        daniel.lezcano@...aro.org, quentin.perret@....com,
        luca.abeni@...tannapisa.it, claudio@...dence.eu.com,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 03/11] cpufreq/schedutil: use rt utilization tracking

On 28-06-18, 17:45, Vincent Guittot wrote:
> Add both cfs and rt utilization when selecting an OPP for cfs tasks as rt
> can preempt and steal cfs's running time.
> 
> rt util_avg is used to take into account the utilization of rt tasks
> on the CPU when selecting OPP. If a rt task migrate, the rt utilization
> will not migrate but will decay over time. On an overloaded CPU, cfs
> utilization reflects the remaining utilization avialable on CPU. When rt
> task migrates, the cfs utilization will increase when tasks will start to
> use the newly available capacity. At the same pace, rt utilization will
> decay and both variations will compensate each other  to keep unchanged
> overall utilization and will prevent any OPP drop.
> 
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
>  kernel/sched/cpufreq_schedutil.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh