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From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [PATCH v2 0/4] allow to skip CQE posting
Date: Wed, 10 Nov 2021 09:14:47 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 11/10/21 8:49 AM, Pavel Begunkov wrote:
> It's expensive enough to post an CQE, and there are other
> reasons to want to ignore them, e.g. for link handling and
> it may just be more convenient for the userspace.
> 
> Try to cover most of the use cases with one flag. The overhead
> is one "if (cqe->flags & IOSQE_CQE_SKIP_SUCCESS)" check per
> requests and a bit bloated req_set_fail(), should be bearable.

I like the idea, one thing I'm struggling with is I think a normal use
case of this would be fast IO where we still need to know if a
completion event has happened, we just don't need to know the details of
it since we already know what those details would be if it ends up in
success.

How about having a skip counter? That would supposedly also allow drain
to work, and it could be mapped with the other cq parts to allow the app
to see it as well.

-- 
Jens Axboe


  parent reply	other threads:[~2021-11-10 16:14 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-10 15:49 [PATCH v2 0/4] allow to skip CQE posting Pavel Begunkov
2021-11-10 15:49 ` [PATCH v2 1/4] io_uring: clean cqe filling functions Pavel Begunkov
2021-11-10 15:49 ` [PATCH v2 2/4] io_uring: add option to skip CQE posting Pavel Begunkov
2021-11-10 15:49 ` [PATCH v2 3/4] io_uring: don't spinlock when not posting CQEs Pavel Begunkov
2021-11-25  3:48   ` Hao Xu
2021-11-25  7:35     ` Hao Xu
2021-11-10 15:49 ` [PATCH v2 4/4] io_uring: disable drain with cqe skip Pavel Begunkov
2021-11-10 16:14 ` Jens Axboe [this message]
2021-11-10 16:42   ` [PATCH v2 0/4] allow to skip CQE posting Pavel Begunkov
2021-11-10 16:47     ` Jens Axboe
2021-11-24 17:55       ` Pavel Begunkov
2021-11-24 17:57         ` Jens Axboe
2021-11-24 18:02           ` Pavel Begunkov
2021-11-24 18:17             ` Jens Axboe
2021-11-25  9:35     ` Hao Xu
2021-11-25 14:22       ` Pavel Begunkov
2021-11-24 18:18 ` Jens Axboe
2021-12-06 19:49   ` Olivier Langlois

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