linux-kernel - Re: EEVDF and NUMA balancing

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Message-ID: <20231004120544.GA6307@noisy.programming.kicks-ass.net>
Date:   Wed, 4 Oct 2023 14:05:44 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: EEVDF and NUMA balancing

On Wed, Oct 04, 2023 at 02:01:26PM +0200, Julia Lawall wrote:
> 
> 
> On Tue, 3 Oct 2023, Peter Zijlstra wrote:
> 
> > On Tue, Oct 03, 2023 at 10:25:08PM +0200, Julia Lawall wrote:
> > > Is it expected that the commit e8f331bcc270 should have an impact on the
> > > frequency of NUMA balancing?
> >
> > Definitely not expected. The only effect of that commit was supposed to
> > be the runqueue order of tasks. I'll go stare at it in the morning --
> > definitely too late for critical thinking atm.
> 
> Maybe it's just randomly making a bad situation worse rather than directly
> introduing a problem.  There is a high standard deviatind in the
> performance.  Here are some results with hyperfine.  The general trends
> are reproducible.

OK,. I'm still busy trying to bring a 4 socket machine up-to-date...
gawd I hate the boot times on those machines :/

But yeah, I was thinking similar things, I really can't spot an obvious
fail in that commit.

I'll go have a poke once the darn machine is willing to submit :-)