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From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[email protected]>, [email protected]
Subject: Re: [RFC][PATCH 0/3] allow to skip CQE posting
Date: Mon, 13 Sep 2021 00:49:00 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 9/11/21 2:51 PM, 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.

FWIW, tried with some benchmark doing QD1 buffered reads, reads
taking 60+% (memcpy/etc.) of the time and 20-25% for io_uring.
Got +6-7% to performance from the kernel side only with additional
room to make the userspace faster.

> 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.
> 
> See 2/3 for the actual description of the flag.
> 
> Pavel Begunkov (3):
>   io_uring: clean cqe filling functions
>   io_uring: add option to skip CQE posting
>   io_uring: don't spinlock when not posting CQEs
> 
>  fs/io_uring.c                 | 103 ++++++++++++++++++++++------------
>  include/uapi/linux/io_uring.h |   3 +
>  2 files changed, 70 insertions(+), 36 deletions(-)
> 

-- 
Pavel Begunkov

      parent reply	other threads:[~2021-09-12 23:49 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-11 13:51 [RFC][PATCH 0/3] allow to skip CQE posting Pavel Begunkov
2021-09-11 13:52 ` [PATCH 1/3] io_uring: clean cqe filling functions Pavel Begunkov
2021-09-12 18:24   ` Hao Xu
2021-09-12 23:20     ` Pavel Begunkov
2021-09-11 13:52 ` [PATCH 2/3] io_uring: add option to skip CQE posting Pavel Begunkov
2021-09-11 13:52 ` [PATCH 3/3] io_uring: don't spinlock when not posting CQEs Pavel Begunkov
2021-09-11 20:12   ` Hao Xu
2021-09-11 21:10     ` Pavel Begunkov
2021-09-12 18:14       ` Hao Xu
2021-09-12 22:16         ` Pavel Begunkov
2021-09-12 23:49 ` Pavel Begunkov [this message]

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