From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [PATCH for-next 0/7] CQ locking optimisation
Date: Tue, 6 Dec 2022 09:53:41 -0700 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 12/4/22 7:44 PM, Pavel Begunkov wrote:
> Optimise CQ locking for event posting depending on a number of ring setup flags.
> QD1 nop benchmark showed 12.067 -> 12.565 MIOPS increase, which more than 8.5%
> of the io_uring kernel overhead (taking into account that the syscall overhead
> is over 50%) or 4.12% of the total performance. Naturally, it's not only about
> QD1, applications can submit a bunch of requests but their completions will may
> arrive randomly hurting batching and so performance (or latency).
>
> The downside is that we have to punt all io-wq completions to the
> original task. The performance win should diminish with better
> completion batching, but it should be worth it for as it also helps tw,
> which in reality often don't complete too many requests.
>
> The feature depends on DEFER_TASKRUN but can be relaxed to SINGLE_ISSUER
Let's hash out the details for MSG_RING later, if we have to.
--
Jens Axboe
next prev parent reply other threads:[~2022-12-06 16:53 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-05 2:44 [PATCH for-next 0/7] CQ locking optimisation Pavel Begunkov
2022-12-05 2:44 ` [PATCH for-next 1/7] io_uring: skip overflow CQE posting for dying ring Pavel Begunkov
2022-12-05 2:44 ` [PATCH for-next 2/7] io_uring: don't check overflow flush failures Pavel Begunkov
2022-12-05 2:44 ` [PATCH for-next 3/7] io_uring: complete all requests in task context Pavel Begunkov
2022-12-05 2:44 ` [PATCH for-next 4/7] io_uring: force multishot CQEs into " Pavel Begunkov
2022-12-05 2:44 ` [PATCH for-next 5/7] io_uring: post msg_ring CQE in " Pavel Begunkov
2022-12-05 11:53 ` Jens Axboe
2022-12-05 15:12 ` Dylan Yudaken
2022-12-05 15:18 ` Jens Axboe
2022-12-06 10:42 ` Pavel Begunkov
2022-12-06 16:06 ` Jens Axboe
2022-12-07 3:59 ` Pavel Begunkov
2022-12-07 15:42 ` Jens Axboe
2022-12-05 2:44 ` [PATCH for-next 6/7] io_uring: use tw for putting rsrc Pavel Begunkov
2022-12-05 2:44 ` [PATCH for-next 7/7] io_uring: skip spinlocking for ->task_complete Pavel Begunkov
2022-12-06 16:53 ` Jens Axboe [this message]
2022-12-06 17:17 ` [PATCH for-next 0/7] CQ locking optimisation Jens Axboe
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