From: Pavel Begunkov <asml.silence@gmail.com>
To: Max Kellermann <max.kellermann@ionos.com>,
axboe@kernel.dk, io-uring@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/8] io_uring: cache io_kiocb->flags in variable
Date: Tue, 4 Feb 2025 12:07:49 +0000 [thread overview]
Message-ID: <fcf5df70-d709-4bec-b4ce-aa833d1d4da2@gmail.com> (raw)
In-Reply-To: <a7733b94-c7c0-4e95-975d-e45562d54f3f@gmail.com>
On 1/29/25 19:11, Pavel Begunkov wrote:
> On 1/28/25 13:39, Max Kellermann wrote:
>> This eliminates several redundant reads, some of which probably cannot
>> be optimized away by the compiler.
>
> Let's not, it hurts readability with no clear benefits. In most cases
> the compiler will be able to optimise it just where it matters, and
> in cold paths we're comparing the overhead of reading a cached variable
> with taking locks and doing indirect calls, and even then it'd likely
> need to be saved onto the stack and loaded back.
>
> The only place where it might be worth it is io_issue_sqe(), and
> even then I'd doubt it.
Jens, I'd suggest to drop it out of the tree, for the reasons above.
--
Pavel Begunkov
next prev parent reply other threads:[~2025-02-04 12:07 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-28 13:39 [PATCH 0/8] Various io_uring micro-optimizations (reducing lock contention) Max Kellermann
2025-01-28 13:39 ` [PATCH 1/8] io_uring/io-wq: eliminate redundant io_work_get_acct() calls Max Kellermann
2025-01-28 13:39 ` [PATCH 2/8] io_uring/io-wq: add io_worker.acct pointer Max Kellermann
2025-01-28 13:39 ` [PATCH 3/8] io_uring/io-wq: move worker lists to struct io_wq_acct Max Kellermann
2025-01-28 13:39 ` [PATCH 4/8] io_uring/io-wq: cache work->flags in variable Max Kellermann
2025-01-29 18:57 ` Pavel Begunkov
2025-01-29 19:11 ` Max Kellermann
2025-01-29 23:41 ` Pavel Begunkov
2025-01-30 5:36 ` Max Kellermann
2025-01-30 14:57 ` Jens Axboe
2025-01-31 14:06 ` Pavel Begunkov
2025-01-30 14:54 ` Jens Axboe
2025-01-28 13:39 ` [PATCH 5/8] io_uring/io-wq: do not use bogus hash value Max Kellermann
2025-01-28 13:39 ` [PATCH 6/8] io_uring/io-wq: pass io_wq to io_get_next_work() Max Kellermann
2025-01-28 13:39 ` [PATCH 7/8] io_uring: cache io_kiocb->flags in variable Max Kellermann
2025-01-29 19:11 ` Pavel Begunkov
2025-02-04 12:07 ` Pavel Begunkov [this message]
2025-02-04 19:45 ` Jens Axboe
2025-01-28 13:39 ` [PATCH 8/8] io_uring: skip redundant poll wakeups Max Kellermann
2025-01-31 13:54 ` Pavel Begunkov
2025-01-31 17:16 ` Max Kellermann
2025-01-31 17:25 ` Pavel Begunkov
2025-01-29 17:18 ` [PATCH 0/8] Various io_uring micro-optimizations (reducing lock contention) Jens Axboe
2025-01-29 17:39 ` Max Kellermann
2025-01-29 17:45 ` Jens Axboe
2025-01-29 18:01 ` Max Kellermann
2025-01-31 16:13 ` Jens Axboe
2025-02-01 15:25 ` Jens Axboe
2025-02-01 15:30 ` Max Kellermann
2025-02-01 15:38 ` Jens Axboe
2025-01-29 19:30 ` Pavel Begunkov
2025-01-29 19:43 ` Max Kellermann
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