linux-kernel - Re: [PATCH v2] sched/fair: Age the average idle time

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Date:   Thu, 17 Jun 2021 16:40:06 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Phil Auld <pauld@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] sched/fair: Age the average idle time

On Thu, Jun 17, 2021 at 11:01:16AM -0400, Phil Auld wrote:
> > Thanks, so far no serious objection :)
> > 
> > The latest results as I see them have been copied to
> > https://beta.suse.com/private/mgorman/melt/v5.13-rc5/3-perf-test/sched/sched-avgidle-v1r6/html/dashboard.html
> > They will move from here if the patch is accepted to 5-assembly replacing
> > 3-perf-test. This naming is part of my workflow for evaluating topic
> > branches separetly and then putting them together for another round
> > of testing.
> > 
> > NAS shows small differences but NAS would see limited impact from the
> > patch. Specjbb shows small losses and some minor gains which is unfortunate
> > but the workload tends to see small gains and losses all the time.
> > redis is a mixed bag but has some wins. hackbench is the main benefit
> > because it's wakeup intensive and tends to overload machines where deep
> > searches hurt.
> > 
> > There are other results in there if you feel like digging around
> > such as sched-core tested with no processes getting tagged with prctl
> > https://beta.suse.com/private/mgorman/melt/v5.13-rc5/5-assembly/sched/sched-schedcore-v1r2/html/dashboard.html
> >
> 
> Thanks for the links. It's cool to see what your results dashboard looks like.
> It's really small, what are you plotting in those heat maps?
> 
> It's hard for me to publish the results that come from our testing (web based
> on intranet) but we don't see any major differences with this patch.  There
> are some gains here and there mostly balanced by some loses.  Overall it comes
> out basically as a wash across our main performance test workload.
> 

Ok, that's unfortunate. It's also somewhat surprising but then again, I
don't know what tests were executed.

> It'll be interesting to see if it effects a sensitive, proprietary perf test
> suite from a European company with a 3 letter name :)
> 

I don't think it's worth the effort if it's failing microbenchmarks at
the moment.

-- 
Mel Gorman
SUSE Labs