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From: Pavel Begunkov <asml.silence@gmail.com>
To: "Jens Axboe" <axboe@kernel.dk>, "Carter Li 李通洲" <carter.li@eoitek.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	io-uring <io-uring@vger.kernel.org>
Subject: Re: [ISSUE] The time cost of IOSQE_IO_LINK
Date: Sun, 16 Feb 2020 22:06:53 +0300
Message-ID: <68a068dd-cb14-10a5-a441-12bc6a2b1dea@gmail.com> (raw)
In-Reply-To: <5cba3020-7d99-56b0-8927-f679118c90e9@kernel.dk>

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On 15/02/2020 09:01, Jens Axboe wrote:
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index fb94b8bac638..530dcd91fa53 100644
> @@ -4630,6 +4753,14 @@ static void __io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>  	 */
>  	if (ret == -EAGAIN && (!(req->flags & REQ_F_NOWAIT) ||
>  	    (req->flags & REQ_F_MUST_PUNT))) {
> +
> +		if (io_arm_poll_handler(req, &retry_count)) {
> +			if (retry_count == 1)
> +				goto issue;

Better to sqe=NULL before retrying, so it won't re-read sqe and try to init the
req twice.

Also, the second sync-issue may -EAGAIN again, and as I remember, read/write/etc
will try to copy iovec into req->io. But iovec is already in req->io, so it will
self memcpy(). Not a good thing.

> +			else if (!retry_count)
> +				goto done_req;
> +			INIT_IO_WORK(&req->work, io_wq_submit_work);

It's not nice to reset it as this:
- prep() could set some work.flags
- custom work.func is more performant (adds extra switch)
- some may rely on specified work.func to be called. e.g. close(), even though
it doesn't participate in the scheme

> +		}
>  punt:
>  		if (io_op_defs[req->opcode].file_table) {
>  			ret = io_grab_files(req);
> @@ -5154,26 +5285,40 @@ void io_uring_task_handler(struct task_struct *tsk)
>  {
>  	LIST_HEAD(local_list);
>  	struct io_kiocb *req;
> +	long state;
>  
>  	spin_lock_irq(&tsk->uring_lock);
>  	if (!list_empty(&tsk->uring_work))

-- 
Pavel Begunkov


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  parent reply index

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12 16:31 Carter Li 李通洲
2020-02-12 17:11 ` Jens Axboe
2020-02-12 17:22   ` Jens Axboe
2020-02-12 17:29     ` Jens Axboe
2020-02-13  0:33   ` Carter Li 李通洲
2020-02-13 15:08     ` Pavel Begunkov
2020-02-13 15:14       ` Jens Axboe
2020-02-13 15:51         ` Carter Li 李通洲
2020-02-14  1:25           ` Carter Li 李通洲
2020-02-14  2:45             ` Jens Axboe
2020-02-14  5:03               ` Jens Axboe
2020-02-14 15:32                 ` Peter Zijlstra
2020-02-14 15:47                   ` Jens Axboe
2020-02-14 16:18                     ` Jens Axboe
2020-02-14 17:52                       ` Jens Axboe
2020-02-14 20:44                         ` Jens Axboe
2020-02-15  0:16                           ` Carter Li 李通洲
2020-02-15  1:10                             ` Jens Axboe
2020-02-15  1:25                               ` Carter Li 李通洲
2020-02-15  1:27                                 ` Jens Axboe
2020-02-15  6:01                                   ` Jens Axboe
2020-02-15  6:32                                     ` Carter Li 李通洲
2020-02-15 15:11                                       ` Jens Axboe
2020-02-16 19:06                                     ` Pavel Begunkov [this message]
2020-02-16 22:23                                       ` Jens Axboe
2020-02-17 10:30                                         ` Pavel Begunkov
2020-02-17 19:30                                           ` Jens Axboe
2020-02-16 23:06                                       ` Jens Axboe
2020-02-16 23:07                                         ` Jens Axboe
2020-02-17 12:09                           ` Peter Zijlstra
2020-02-17 16:12                             ` Jens Axboe
2020-02-17 17:16                               ` Jens Axboe
2020-02-17 17:46                                 ` Peter Zijlstra
2020-02-17 18:16                                   ` Jens Axboe
2020-02-18 13:13                                     ` Peter Zijlstra
2020-02-18 14:27                                       ` [PATCH] asm-generic/atomic: Add try_cmpxchg() fallbacks Peter Zijlstra
2020-02-18 14:40                                         ` Peter Zijlstra
2020-02-20 10:30                                         ` Will Deacon
2020-02-20 10:37                                           ` Peter Zijlstra
2020-02-20 10:39                                             ` Will Deacon
2020-02-18 14:56                                       ` [ISSUE] The time cost of IOSQE_IO_LINK Oleg Nesterov
2020-02-18 15:07                                         ` Oleg Nesterov
2020-02-18 15:38                                           ` Peter Zijlstra
2020-02-18 16:33                                             ` Jens Axboe
2020-02-18 15:07                                         ` Peter Zijlstra
2020-02-18 15:50                                           ` [PATCH] task_work_run: don't take ->pi_lock unconditionally Oleg Nesterov
2020-02-20 16:39                                             ` Peter Zijlstra
2020-02-20 17:22                                               ` Oleg Nesterov
2020-02-20 17:49                                                 ` Peter Zijlstra
2020-02-21 14:52                                                   ` Oleg Nesterov
2020-02-24 18:47                                                     ` Jens Axboe
2020-02-28 19:17                                                       ` Jens Axboe
2020-02-28 19:25                                                         ` Peter Zijlstra
2020-02-28 19:28                                                           ` Jens Axboe
2020-02-28 20:06                                                             ` Peter Zijlstra
2020-02-28 20:15                                                               ` Jens Axboe
2020-02-18 16:46                                       ` [ISSUE] The time cost of IOSQE_IO_LINK Jens Axboe
2020-02-18 16:52                                         ` Jens Axboe
2020-02-18 13:13                               ` Peter Zijlstra

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