linux-kernel - Re: [PATCH v4 1/6] x86,sched: Add support for frequency invariance

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Date:   Mon, 25 Nov 2019 17:06:01 +0100
From:   Giovanni Gherdovich <ggherdovich@...e.cz>
To:     Doug Smythies <dsmythies@...us.net>,
        'Srinivas Pandruvada' <srinivas.pandruvada@...ux.intel.com>,
        'Thomas Gleixner' <tglx@...utronix.de>,
        'Ingo Molnar' <mingo@...hat.com>,
        'Peter Zijlstra' <peterz@...radead.org>,
        'Borislav Petkov' <bp@...e.de>, 'Len Brown' <lenb@...nel.org>,
        "'Rafael J . Wysocki'" <rjw@...ysocki.net>
Cc:     x86@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        'Mel Gorman' <mgorman@...hsingularity.net>,
        'Matt Fleming' <matt@...eblueprint.co.uk>,
        'Viresh Kumar' <viresh.kumar@...aro.org>,
        'Juri Lelli' <juri.lelli@...hat.com>,
        'Paul Turner' <pjt@...gle.com>,
        'Vincent Guittot' <vincent.guittot@...aro.org>,
        'Quentin Perret' <qperret@...rret.net>,
        'Dietmar Eggemann' <dietmar.eggemann@....com>
Subject: Re: [PATCH v4 1/6] x86,sched: Add support for frequency invariance

On Sat, 2019-11-23 at 23:49 -0800, Doug Smythies wrote:
> ...
> Kernel 5.4-rc8 + revert, intel_cpufreq/schedutil: 3899 seconds
> Kernel 5.4-rc8 + gg 6 + revert, intel_cpufreq/schedutil: 2740.7 seconds
> Ratio: 0.70 (as expected)
> Kernel 5.4-rc8, intel_cpufreq/schedutil: 2334.7 seconds (faster than expected)
> Kernel 5.4-rc8 + gg 6 patch set, intel_cpufreq/schedutil: 2275.0 seconds (faster than expected)
> Ratio: 0.97 (not as expected)
> Kernel 5.4-rc8, intel_cpufreq/performance: 2215.3 seconds
> Kernel 5.4-rc8, intel_cpufreq/ondemand: 3286.3 seconds
> Re-stated from previous e-mail:
> Kernel 5.3-rc8, intel_cpufreq/schedutil: ratio: 0.69 (I don't have the original times)

Hello Doug,

schedutil in 5.4 going a lot faster than in 5.3 would be a surprise. I'm
running that same test too to check if I can see it as well.

Besides, as it's already been said this patchset adds frequency
scale-invariance to scheduler metrics such as load and utilization and that's
useful also in areas other than frequency scaling (most notably the scheduler
load balancer).


Thanks,
Giovanni