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Date: Fri, 27 May 2016 13:41:02 +0800
Message-ID: <CANRm+Cyfi=u32ZWqqPfo+FxbTKayGhQZ5C97pQ5EBSRi84PA_w@mail.gmail.com>
Subject: Re: [PATCH v2 3/3] cpufreq: schedutil: map raw required frequency to
 driver frequency
From: Wanpeng Li <kernellwp@gmail.com>
To: Steve Muckle <steve.muckle@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux PM list <linux-pm@vger.kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Juri Lelli <Juri.Lelli@arm.com>,
        Patrick Bellasi <patrick.bellasi@arm.com>,
        Michael Turquette <mturquette@baylibre.com>
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2016-05-26 10:53 GMT+08:00 Steve Muckle <steve.muckle@linaro.org>:
> The slow-path frequency transition path is relatively expensive as it
> requires waking up a thread to do work. Should support be added for
> remote CPU cpufreq updates that is also expensive since it requires an
> IPI. These activities should be avoided if they are not necessary.
>
> To that end, calculate the actual driver-supported frequency required by
> the new utilization value in schedutil by using the recently added
> cpufreq_driver_resolve_freq callback. If it is the same as the
> previously requested driver frequency then there is no need to continue
> with the update assuming the cpu frequency limits have not changed. This
> will have additional benefits should the semantics of the rate limit be
> changed to apply solely to frequency transitions rather than to
> frequency calculations in schedutil.

sugov_should_update_freq() still be called before get_nex_freq() after
the patch applied, so rate limit still apply to both frequency
transitions and frequency calculations, right?

Regards,
Wanpeng Li