linux-kernel - Re: [RFC 4/4] io_uring: implement futex wait

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Date:   Tue, 1 Jun 2021 09:45:22 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>, io-uring@...r.kernel.org
Cc:     Andres Freund <andres@...razel.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC 4/4] io_uring: implement futex wait

On 6/1/21 8:58 AM, Pavel Begunkov wrote:
> Add futex wait requests, those always go through io-wq for simplicity.

Not a huge fan of that, I think this should tap into the waitqueue
instead and just rely on the wakeup callback to trigger the event. That
would be a lot more efficient than punting to io-wq, both in terms of
latency on trigger, but also for efficiency if the app is waiting on a
lot of futexes.

-- 
Jens Axboe