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 <20221116105725.6hyyexgwexo52i5j@suse.de>
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From:   Andrei Vagin <avagin@gmail.com>
Date:   Wed, 16 Nov 2022 10:50:03 -0800
Message-ID: <CANaxB-yEgFuDZZ3w3JudNOSJr3tZfmbYgZ+txhBSc8WHXGRvaA@mail.gmail.com>
Subject: Re: [PATCH] sched: consider WF_SYNC to find idle siblings
To:     Mel Gorman <mgorman@suse.de>, kprateek.nayak@amd.com
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Andrei Vagin <avagin@google.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        linux-kernel@vger.kernel.org,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>
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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@suse.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