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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Wed, 10 Oct 2018 14:34:32 +0200
Message-ID: <CAKfTPtCVryjWWT_M1zEZfJUjGkt2JPUiBK6vt0YiJTK4qVoqbA@mail.gmail.com>
Subject: Re: [RFC PATCH 0/7] Introduce thermal pressure
To:     Juri Lelli <juri.lelli@gmail.com>
Cc:     Quentin Perret <quentin.perret@arm.com>,
        Ingo Molnar <mingo@kernel.org>,
        Thara Gopinath <thara.gopinath@linaro.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Zhang Rui <rui.zhang@intel.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Amit Kachhap <amit.kachhap@gmail.com>,
        viresh kumar <viresh.kumar@linaro.org>,
        Javi Merino <javi.merino@kernel.org>,
        Eduardo Valentin <edubezval@gmail.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        "open list:THERMAL" <linux-pm@vger.kernel.org>,
        Ionela Voinescu <ionela.voinescu@arm.com>
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Hi  Juri,

On Wed, 10 Oct 2018 at 14:23, Juri Lelli <juri.lelli@gmail.com> wrote:
>
> On 10/10/18 14:04, Vincent Guittot wrote:
>
> [...]
>
> > The problem was the same with RT, the cfs utilization was lower than
> > reality because RT steals soem cycle to CFS
> > So schedutil was selecting a lower frequency when cfs was running
> > whereas the CPU was fully used.
> > The same can happen with thermal:
> > cap the max freq because of thermal
> > the utilization with decrease.
> > remove the cap
> > the utilization is still low and you will select a low OPP because you
> > don't take into account cycle stolen by thermal like with RT
>
> What if we scale frequency component considering the capped temporary
> max?

Do you mean using a kind of scale_thermal_capacity in accumulate_sum
when computing utilization ?