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From: Ming Lei <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Pavel Begunkov <[email protected]>,
	Christoph Hellwig <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected], [email protected],
	[email protected], [email protected]
Subject: Re: [PATCH for-next 2/2] nvme: optimise io_uring passthrough completion
Date: Thu, 18 May 2023 10:15:42 +0800	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On Wed, May 17, 2023 at 01:31:00PM -0600, Jens Axboe wrote:
> On 5/17/23 6:32 AM, Pavel Begunkov wrote:
> > On 5/17/23 08:23, Christoph Hellwig wrote:
> >> On Mon, May 15, 2023 at 01:54:43PM +0100, Pavel Begunkov wrote:
> >>> Use IOU_F_TWQ_LAZY_WAKE via iou_cmd_exec_in_task_lazy() for passthrough
> >>> commands completion. It further delays the execution of task_work for
> >>> DEFER_TASKRUN until there are enough of task_work items queued to meet
> >>> the waiting criteria, which reduces the number of wake ups we issue.
> >>
> >> Why wouldn't you just do that unconditionally for
> >> io_uring_cmd_complete_in_task?
> > 
> > 1) ublk does secondary batching and so may produce multiple cqes,
> > that's not supported. I believe Ming sent patches removing it,
> > but I'd rather not deal with conflicts for now.
> 
> Ming, what's the status of those patches? Looks like we'll end up
> with a dependency regardless of the ordering of these. Since these
> patches are here now, sanest approach seems to move forward with
> this series and defer the conflict resolving to the ublk side.

I didn't send patch to remove the batch in ublk, such as, the following
line code:

ublk_queue_cmd():
	...
	if (!llist_add(&data->node, &ubq->io_cmds))
		return;
	...

But I did want to kill it given __io_req_task_work_add() can do batching
process, but we have to re-order request in this list, so can't remove it
now simply, see commit:

	7d4a93176e01 ("ublk_drv: don't forward io commands in reserve order")

Pavel must have misunderstood the following one as the batch removal:

https://lore.kernel.org/linux-block/[email protected]/

	

thanks,
Ming


  reply	other threads:[~2023-05-18  2:16 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-15 12:54 [PATCH for-next 0/2] Enable IOU_F_TWQ_LAZY_WAKE for passthrough Pavel Begunkov
2023-05-15 12:54 ` [PATCH for-next 1/2] io_uring/cmd: add cmd lazy tw wake helper Pavel Begunkov
2023-05-16 10:00   ` Kanchan Joshi
2023-05-16 18:52     ` Pavel Begunkov
2023-05-17 10:33       ` Kanchan Joshi
2023-05-17 12:00         ` Pavel Begunkov
2023-05-19 15:00         ` Pavel Begunkov
2023-05-15 12:54 ` [PATCH for-next 2/2] nvme: optimise io_uring passthrough completion Pavel Begunkov
2023-05-17  7:23   ` Christoph Hellwig
2023-05-17 12:32     ` Pavel Begunkov
2023-05-17 12:39       ` Christoph Hellwig
2023-05-17 13:30         ` Pavel Begunkov
2023-05-17 13:53           ` Christoph Hellwig
2023-05-17 20:11             ` Pavel Begunkov
2023-05-17 19:31       ` Jens Axboe
2023-05-18  2:15         ` Ming Lei [this message]
2023-05-16 11:42 ` [PATCH for-next 0/2] Enable IOU_F_TWQ_LAZY_WAKE for passthrough Anuj gupta
2023-05-16 18:38   ` Pavel Begunkov
2023-05-25 14:54 ` Jens Axboe

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