linux-kernel - Re: [PATCH 4/4] sched/fair: Use a recently used CPU as an idle candidate and the basis for SIS

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Date:   Tue, 30 Jan 2018 13:18:59 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mike Galbraith <efault@....de>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] sched/fair: Use a recently used CPU as an idle
 candidate and the basis for SIS

On Tue, Jan 30, 2018 at 02:06:06PM +0100, Peter Zijlstra wrote:
> On Tue, Jan 30, 2018 at 12:53:49PM +0100, Peter Zijlstra wrote:
> > On Tue, Jan 30, 2018 at 10:45:55AM +0000, Mel Gorman wrote:
> > > The results can be less dramatic on NUMA where automatic balancing interferes
> > > with the test. It's also known that network benchmarks running on localhost
> > > also benefit quite a bit from this patch (roughly 10% on netperf RR for UDP
> > > and TCP depending on the machine). Hackbench also seens small improvements
> > > (6-11% depending on machine and thread count). The facebook schbench was also
> > > tested but in most cases showed little or no different to wakeup latencies.
> > 
> > What cpufreq setting were you using for these tests?
> 
> I cannot measure any hackbench variation one way or the other with these
> patches using 'performance' mode. So I'll assume you've been running
> things with HWP or something.

Correct, I am not using the performance governor as it's not the default and
not necessarily desirable as a default.  HWP in some cases is enabled but
even machines using the intel_pstate driver on machines without HWP benefit.

-- 
Mel Gorman
SUSE Labs