linux-kernel - Re: [PATCH 1/2] io_uring: clear TIF_NOTIFY

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Date:   Tue, 10 Aug 2021 09:33:30 -0400
From:   Olivier Langlois <olivier@...llion01.com>
To:     Nadav Amit <nadav.amit@...il.com>
Cc:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Pavel Begunkov <asml.silence@...il.com>
Subject: Re: [PATCH 1/2] io_uring: clear TIF_NOTIFY_SIGNAL when running task
 work

On Tue, 2021-08-10 at 01:28 -0700, Nadav Amit wrote:
> 
> Happy it could help.
> 
> Unfortunately, there seems to be yet another issue (unless my code
> somehow caused it). It seems that when SQPOLL is used, there are
> cases
> in which we get stuck in io_uring_cancel_sqpoll() when
> tctx_inflight()
> never goes down to zero.
> 
> Debugging... (while also trying to make some progress with my code)

You are on something. io_uring starts to be very solid but it isn't
100% flawless yet.

I am a heavy user of SQPOLL which now run flawlessly for me with 5.13.9
(Was running flawlessly since 5.12 minus few patches I did submit
recently) with my simple use-case (my SQPOLL thread isn't spawning any
threads like in your use-case).

The best is yet to come. I'm salivating by seeing all the performance
optimizations that Jens and Pavel are putting in place lately...