linux-kernel - Re: [RFC PATCH v4 00/19] Core scheduling v4

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Message-ID: <CAERHkrtraNqWj+RZnUFBaR8Cxk_cprQnzyKEgZ=6K+1mb1Jifw@mail.gmail.com>
Date:   Tue, 25 Feb 2020 18:40:02 +0800
From:   Aubrey Li <aubrey.intel@...il.com>
To:     Aaron Lu <aaron.lwe@...il.com>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Vineeth Remanan Pillai <vpillai@...italocean.com>,
        Nishanth Aravamudan <naravamudan@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Turner <pjt@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Dario Faggioli <dfaggioli@...e.com>,
        Frédéric Weisbecker <fweisbec@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Kerr <kerrnel@...gle.com>, Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [RFC PATCH v4 00/19] Core scheduling v4

On Tue, Feb 25, 2020 at 3:34 PM Aaron Lu <aaron.lwe@...il.com> wrote:
>
> On Tue, Feb 25, 2020 at 01:32:35PM +0800, Aubrey Li wrote:
> > Aaron - did you test this before? In other words, if you reset repo to your
> > last commit:
>
> I did this test only recently when I started to think if I can use
> coresched to boost main workload's performance in a colocated
> environment.
>
> >
> > - 5bd3c80 sched/fair : Wake up forced idle siblings if needed
> >
> > Does the problem remain? Just want to check if this is a regression
> >  introduced by the subsequent patchset.
>
> The problem isn't there with commit 5bd3c80 as the head, so yes, it
> looks like indeed a regression introduced by subsequent patchset.
>
> P.S. I will need to take a closer look if each cgA's task is running
> on a different core later but the cpu usage of cgA is back to 800% with
> commit 5bd3c80.

Hmm..., I went through the subsequent patches, and I think this one

- 4041eeb8f3 sched/fair: don't migrate task if cookie not match

is probably the major cause, can you please revert this one to see
if the problem is gone?

>From what I can tell, if 16 threads in cgB occupied 8 cores, this
patch prevents any thread in cgA from migrating when load balance
is triggered, and yes, cpu.shares is ignored at this point.

Thanks,
-Aubrey