From: Pavel Begunkov <[email protected]>
To: Christoph Hellwig <[email protected]>
Cc: [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: Wed, 17 May 2023 13:32:53 +0100 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
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.
2) Some users may have dependencies b/w requests, i.e. a request
will only complete when another request's task_work is executed.
3) There might be use cases when you don't wont it to be delayed,
IO retries would be a good example. I wouldn't also use it for
control paths like ublk_ctrl_uring_cmd.
Let's better keep io_uring_cmd_complete_in_task() as the default
option for the interface.
--
Pavel Begunkov
next prev parent reply other threads:[~2023-05-17 12:36 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 [this message]
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
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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