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From: Pavel Begunkov <[email protected]>
To: Hao Xu <[email protected]>, Jens Axboe <[email protected]>
Cc: [email protected], Joseph Qi <[email protected]>
Subject: Re: [PATCH 4/6] io_uring: let fast poll support multishot
Date: Mon, 6 Sep 2021 20:09:14 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 9/6/21 6:40 PM, Hao Xu wrote:
> 在 2021/9/6 下午11:56, Pavel Begunkov 写道:
>> On 9/3/21 12:00 PM, Hao Xu wrote:
>>> For operations like accept, multishot is a useful feature, since we can
>>> reduce a number of accept sqe. Let's integrate it to fast poll, it may
>>> be good for other operations in the future.
>>
>> __io_arm_poll_handler()         |
>>    -> vfs_poll()                 |
>>                                  | io_async_task_func() // post CQE
>>                                  | ...
>>                                  | do_apoll_rewait();
>>    -> continues after vfs_poll(),|
>>       removing poll->head of     |
>>       the second poll attempt.   |
>>
>>
> Sorry.. a little bit confused by this case, would you mind explain a bit
> more..is the right part a system-workqueue context? and is
> do_apoll_rewait() io_poll_rewait() function?

I meant in a broad sense. If your patches make lifetime of an accept
request to be like:

accept() -> arm_apoll() -> apoll_func() -> accept() -> ...
    -> ... (repeat many times)

then do_apoll_rewait() is the second accept in the scheme.

If not, and it's

accept() -> arm_poll() -> apoll_func() -> apoll_func() ->
 ... -> ?

Then that "do_apoll_rewait()" should have been second and
other apoll_func()s.

So, it's rather a thing to look after, but not a particular
bug.


>> One of the reasons for forbidding multiple apoll's is that it
>> might be racy. I haven't looked into this implementation, but
>> we should check if there will be problems from that.
>>
>> FWIW, putting aside this patchset, the poll/apoll is not in
>> the best shape and can use some refactoring.
>>
>>
[...]

-- 
Pavel Begunkov

  reply	other threads:[~2021-09-06 19:09 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-03 11:00 [RFC 0/6] fast poll multishot mode Hao Xu
2021-09-03 11:00 ` [PATCH 1/6] io_uring: enhance flush completion logic Hao Xu
2021-09-03 11:42   ` Pavel Begunkov
2021-09-03 12:08     ` Hao Xu
2021-09-03 12:27       ` Pavel Begunkov
2021-09-03 13:38         ` Hao Xu
2021-09-17 18:49           ` Hao Xu
2021-09-03 11:00 ` [PATCH 2/6] io_uring: add IORING_ACCEPT_MULTISHOT for accept Hao Xu
2021-09-03 11:00 ` [PATCH 3/6] io_uring: add REQ_F_APOLL_MULTISHOT for requests Hao Xu
2021-09-03 11:00 ` [PATCH 4/6] io_uring: let fast poll support multishot Hao Xu
2021-09-06 15:56   ` Pavel Begunkov
2021-09-06 17:40     ` Hao Xu
2021-09-06 19:09       ` Pavel Begunkov [this message]
2021-09-07  6:38         ` Hao Xu
2021-09-06 19:04   ` Pavel Begunkov
2021-09-07  6:48     ` Hao Xu
2021-09-08 11:21       ` Hao Xu
2021-09-08 12:03         ` Pavel Begunkov
2021-09-08 13:13           ` Pavel Begunkov
2021-09-09  7:01           ` Hao Xu
2021-09-09  8:29             ` Hao Xu
2021-09-11 10:49               ` Pavel Begunkov
2021-09-11 20:19                 ` Hao Xu
2021-09-03 11:00 ` [PATCH 5/6] io_uring: implement multishot mode for accept Hao Xu
2021-09-04 22:39   ` Pavel Begunkov
2021-09-04 22:40     ` Pavel Begunkov
2021-09-06 15:34       ` Pavel Begunkov
2021-09-03 11:00 ` [PATCH 6/6] io_uring: enable " Hao Xu
2021-09-03 16:29   ` Jens Axboe
2021-09-04 15:34     ` Hao Xu
2021-09-04 18:40       ` Jens Axboe
2021-09-04 22:46         ` Pavel Begunkov
2021-09-05  7:29           ` Hao Xu
2021-09-05 19:44           ` Jens Axboe
2021-09-06  8:26             ` Hao Xu
2021-09-06  8:28               ` Hao Xu
2021-09-06 13:24               ` Jens Axboe
2021-09-06 12:35             ` Hao Xu
2021-09-06 13:31               ` Jens Axboe
2021-09-06 15:00                 ` Hao Xu
2021-09-06 15:32               ` Pavel Begunkov
2021-09-06 16:42                 ` Jens Axboe
2021-09-04 22:43   ` Pavel Begunkov
2021-09-05  6:25     ` Hao Xu
2021-09-05  8:27       ` Pavel Begunkov
2021-09-03 11:02 ` [RFC 0/6] fast poll multishot mode Hao Xu

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