linux-kernel - Re: [RFCv7 PATCH 00/10] sched: scheduler-driven CPU frequency selection

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Date:	Thu, 31 Mar 2016 04:22:18 +0800
From:	Yuyang Du <yuyang.du@...el.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>,
	linux-kernel@...r.kernel.org, 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: [RFCv7 PATCH 00/10] sched: scheduler-driven CPU frequency
 selection

Hi Steve,

On Wed, Mar 30, 2016 at 06:35:23PM -0700, Steve Muckle wrote:
> This series was dropped in favor of Rafael's schedutil. But on the
> chance that you're still curious about the test setup used to quantify
> the series I'll explain below.
 
I will catch up and learn both.

> These results are meant to show how the governors perform across varying
> workload intensities and periodicities. Higher overhead (OH) numbers
> indicate that the completion times of each period of the workload were
> closer to what they would be when run at fmin (100% overhead would be as
> slow as fmin, 0% overhead would be as fast as fmax). And as described
> above, overruns (OR) indicate that the governor was not responsive
> enough to finish the work in each period of the workload.
> 
> These are just performance metrics so they only tell half the story.
> Power is not factored in at all.
> 
> This provides a quick sanity check that the governor under test (in this
> case, the now defunct schedfreq, or sched for short) performs similarly
> to two of the most commonly used governors, ondemand and interactive, in
> steady state periodic workloads. In the data above sched looks good for
> the most part with the second test case being the biggest exception.
 
Yes, it is indeed a quick sanity check.

Thanks,
Yuyang