linux-kernel - Re: [PATCH] sched: consider WF

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Date:   Wed, 16 Nov 2022 10:50:03 -0800
From:   Andrei Vagin <avagin@...il.com>
To:     Mel Gorman <mgorman@...e.de>, kprateek.nayak@....com
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andrei Vagin <avagin@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel@...r.kernel.org,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>
Subject: Re: [PATCH] sched: consider WF_SYNC to find idle siblings

Hello Mel and Prateek,

Thank you both for running tests and publishing results here.

On Wed, Nov 16, 2022 at 2:57 AM Mel Gorman <mgorman@...e.de> wrote:
<snip>
>
> This is not too surprising as UDP_STREAM is blasting packets so there are
> wakeups but the waker is not going to sleep immediately. So yeah, there are
> cases where the patch helps but when it hurts, it can hurt a lot. The patch
> certainly demonstrates that there is room for improvement on how WF_SYNC is
> treated but as it stands, it would start a game of apply/revert ping-pong
> as different bisections showed the patch caused one set of problems and
> the revert caused another.

I agree with these conclusions. The situation is more complex than how
I saw it initially.

Thanks,
Andrei