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From: Peter Zijlstra <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Jann Horn <[email protected]>, io-uring <[email protected]>,
	Glauber Costa <[email protected]>,
	Pavel Begunkov <[email protected]>
Subject: Re: [PATCH 7/9] io_uring: add per-task callback handler
Date: Fri, 21 Feb 2020 17:23:54 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On Fri, Feb 21, 2020 at 06:49:16AM -0800, Jens Axboe wrote:

> > Jens, what exactly is the benefit of running this on every random
> > schedule() vs in io_cqring_wait() ? Or even, since io_cqring_wait() is
> > the very last thing the syscall does, task_work.
> 
> I took a step back and I think we can just use the task work, which
> makes this a lot less complicated in terms of locking and schedule
> state. Ran some quick testing with the below and it works for me.
> 
> I'm going to re-spin based on this and just dump the sched_work
> addition.

Aswesome, simpler is better.

> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 81aa3959f326..413ac86d7882 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -3529,7 +3529,7 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
>  	 * the exit check will ultimately cancel these work items. Hence we
>  	 * don't need to check here and handle it specifically.
>  	 */
> -	sched_work_add(tsk, &req->sched_work);
> +	task_work_add(tsk, &req->sched_work, true);
>  	wake_up_process(tsk);
>  	return 1;
>  }
> @@ -5367,9 +5367,9 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
>  	do {
>  		if (io_cqring_events(ctx, false) >= min_events)
>  			return 0;
> -		if (!current->sched_work)
> +		if (!current->task_works)
>  			break;
> -		sched_work_run();
> +		task_work_run();
>  	} while (1);
>  
>  	if (sig) {
> @@ -5392,6 +5392,12 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
>  						TASK_INTERRUPTIBLE);
>  		if (io_should_wake(&iowq, false))
>  			break;
> +		if (current->task_works) {
> +			task_work_run();
> +			if (io_should_wake(&iowq, false))
> +				break;
> +			continue;
> +		}

		if (current->task_works)
			task_work_run();
		if (io_should_wake(&iowq, false);
			break;

doesn't work?

>  		schedule();
>  		if (signal_pending(current)) {
>  			ret = -EINTR;


Anyway, we need to be careful about the context where we call
task_work_run(), but afaict doing it here should be fine.

  parent reply	other threads:[~2020-02-21 16:23 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-20 20:31 [PATCHSET 0/9] io_uring: use polled async retry Jens Axboe
2020-02-20 20:31 ` [PATCH 1/9] io_uring: consider any io_read/write -EAGAIN as final Jens Axboe
2020-02-20 20:31 ` [PATCH 2/9] io_uring: io_accept() should hold on to submit reference on retry Jens Axboe
2020-02-20 20:31 ` [PATCH 3/9] sched: move io-wq/workqueue worker sched in/out into helpers Jens Axboe
2020-02-20 20:31 ` [PATCH 4/9] task_work_run: don't take ->pi_lock unconditionally Jens Axboe
2020-02-20 20:31 ` [PATCH 5/9] kernel: abstract out task work helpers Jens Axboe
2020-02-20 21:07   ` Peter Zijlstra
2020-02-20 21:08     ` Jens Axboe
2020-02-20 20:31 ` [PATCH 6/9] sched: add a sched_work list Jens Axboe
2020-02-20 21:17   ` Peter Zijlstra
2020-02-20 21:53     ` Jens Axboe
2020-02-20 22:02       ` Jens Axboe
2020-02-20 20:31 ` [PATCH 7/9] io_uring: add per-task callback handler Jens Axboe
2020-02-20 22:02   ` Jann Horn
2020-02-20 22:14     ` Jens Axboe
2020-02-20 22:18       ` Jens Axboe
2020-02-20 22:25         ` Jann Horn
2020-02-20 22:23       ` Jens Axboe
2020-02-20 22:38         ` Jann Horn
2020-02-20 22:56           ` Jens Axboe
2020-02-20 22:58             ` Jann Horn
2020-02-20 23:02               ` Jens Axboe
2020-02-20 22:23       ` Jann Horn
2020-02-20 23:00         ` Jens Axboe
2020-02-20 23:12           ` Jann Horn
2020-02-20 23:22             ` Jens Axboe
2020-02-21  1:29               ` Jann Horn
2020-02-21 17:32                 ` Jens Axboe
2020-02-21 19:24                   ` Jann Horn
2020-02-21 20:18                     ` Jens Axboe
2020-02-20 22:56     ` Jann Horn
2020-02-21 10:47     ` Peter Zijlstra
2020-02-21 14:49       ` Jens Axboe
2020-02-21 15:02         ` Jann Horn
2020-02-21 16:12           ` Peter Zijlstra
2020-02-21 16:23         ` Peter Zijlstra [this message]
2020-02-21 20:13           ` Jens Axboe
2020-02-21 13:51   ` Pavel Begunkov
2020-02-21 14:50     ` Jens Axboe
2020-02-21 18:30       ` Pavel Begunkov
2020-02-21 19:10         ` Jens Axboe
2020-02-21 19:22           ` Pavel Begunkov
2020-02-23  6:00           ` Jens Axboe
2020-02-23  6:26             ` Jens Axboe
2020-02-23 11:02               ` Pavel Begunkov
2020-02-23 14:49                 ` Jens Axboe
2020-02-23 14:58                   ` Jens Axboe
2020-02-23 15:07                     ` Jens Axboe
2020-02-23 18:04                       ` Pavel Begunkov
2020-02-23 18:06                         ` Jens Axboe
2020-02-23 17:55                   ` Pavel Begunkov
2020-02-20 20:31 ` [PATCH 8/9] io_uring: mark requests that we can do poll async in io_op_defs Jens Axboe
2020-02-20 20:31 ` [PATCH 9/9] io_uring: use poll driven retry for files that support it Jens Axboe

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