linux-kernel - Re: [PATCH v2 3/3] cpufreq: schedutil: map raw required frequency to driver frequency

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Message-ID: <CANRm+Cyfi=u32ZWqqPfo+FxbTKayGhQZ5C97pQ5EBSRi84PA_w@mail.gmail.com>
Date:	Fri, 27 May 2016 13:41:02 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	Steve Muckle <steve.muckle@...aro.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Juri Lelli <Juri.Lelli@....com>,
	Patrick Bellasi <patrick.bellasi@....com>,
	Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH v2 3/3] cpufreq: schedutil: map raw required frequency to
 driver frequency

2016-05-26 10:53 GMT+08:00 Steve Muckle <steve.muckle@...aro.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