From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>,
io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] io_uring: don't wait when under-submitting
Date: Sun, 15 Dec 2019 18:48:20 +0300 [thread overview]
Message-ID: <900dbb63-ae9e-40e6-94f9-8faa1c14389e@gmail.com> (raw)
In-Reply-To: <3a102881-3cc3-ba05-2f86-475145a87566@kernel.dk>
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On 15/12/2019 08:42, Jens Axboe wrote:
> On 12/14/19 11:43 AM, Jens Axboe wrote:
>> On 12/14/19 7:53 AM, Pavel Begunkov wrote:
>>> There is no reliable way to submit and wait in a single syscall, as
>>> io_submit_sqes() may under-consume sqes (in case of an early error).
>>> Then it will wait for not-yet-submitted requests, deadlocking the user
>>> in most cases.
>>>
>>> In such cases adjust min_complete, so it won't wait for more than
>>> what have been submitted in the current call to io_uring_enter(). It
>>> may be less than totally in-flight including previous submissions,
>>> but this shouldn't do harm and up to a user.
>>
>> Thanks, applied.
>
> This causes a behavioral change where if you ask to submit 1 but
> there's nothing in the SQ ring, then you would get 0 before. Now
> you get -EAGAIN. This doesn't make a lot of sense, since there's no
> point in retrying as that won't change anything.
>
> Can we please just do something like the one I sent, instead of trying
> to over-complicate it?
>
Ok, when I get to a compiler.
--
Pavel Begunkov
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next prev parent reply other threads:[~2019-12-15 15:48 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-13 7:51 [PATCH 1/1] io_uring: don't wait when under-submitting Pavel Begunkov
2019-12-13 18:22 ` Jens Axboe
2019-12-13 18:32 ` Jens Axboe
2019-12-13 21:32 ` Pavel Begunkov
2019-12-13 21:48 ` Jens Axboe
2019-12-14 14:31 ` [PATCH v2] " Pavel Begunkov
2019-12-14 14:39 ` Jens Axboe
2019-12-14 14:44 ` Pavel Begunkov
2019-12-14 14:53 ` [PATCH v3] " Pavel Begunkov
2019-12-14 18:43 ` Jens Axboe
2019-12-15 5:42 ` Jens Axboe
2019-12-15 15:48 ` Pavel Begunkov [this message]
2019-12-15 21:33 ` Jens Axboe
2019-12-16 16:31 ` [PATCH v4] " Pavel Begunkov
2019-12-16 16:47 ` [PATCH v3] " Pavel Begunkov
2019-12-16 16:51 ` Jens Axboe
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