linux-kernel - Re: [PATCH] io_uring: reduce latency by reissueing the operation

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Message-ID: <ff0aab90-9aef-4ec6-f00f-89d4ffa21ef6@kernel.dk>
Date:   Wed, 16 Jun 2021 06:48:52 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Olivier Langlois <olivier@...llion01.com>,
        Pavel Begunkov <asml.silence@...il.com>,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] io_uring: reduce latency by reissueing the operation

On 6/9/21 4:08 PM, Olivier Langlois wrote:
> It is quite frequent that when an operation fails and returns EAGAIN,
> the data becomes available between that failure and the call to
> vfs_poll() done by io_arm_poll_handler().
> 
> Detecting the situation and reissuing the operation is much faster
> than going ahead and push the operation to the io-wq.

I think this is obviously the right thing to do, but I'm not too crazy
about the 'ret' pointer passed in. We could either add a proper return
type instead of the bool and use that, or put the poll-or-queue-async
into a helper that then only needs a bool return, and use that return
value for whether to re-issue or not.

Care to send an updated variant?

-- 
Jens Axboe