public inbox for [email protected]
 help / color / mirror / Atom feed
From: Pavel Begunkov <[email protected]>
To: Olivier Langlois <[email protected]>,
	Jens Axboe <[email protected]>,
	[email protected], [email protected]
Subject: Re: [PATCH v4] io_uring: reduce latency by reissueing the operation
Date: Tue, 22 Jun 2021 21:51:28 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 6/22/21 8:05 PM, Olivier Langlois wrote:
> On Tue, 2021-06-22 at 19:01 +0100, Pavel Begunkov wrote:
>> On 6/22/21 6:54 PM, Pavel Begunkov wrote:
>>> On 6/22/21 1:17 PM, Olivier Langlois wrote:
>>>>
>>>
>>>>  static bool __io_poll_remove_one(struct io_kiocb *req,
>>>> @@ -6437,6 +6445,7 @@ static void __io_queue_sqe(struct io_kiocb
>>>> *req)
>>>>         struct io_kiocb *linked_timeout =
>>>> io_prep_linked_timeout(req);
>>>>         int ret;
>>>>  
>>>> +issue_sqe:
>>>>         ret = io_issue_sqe(req,
>>>> IO_URING_F_NONBLOCK|IO_URING_F_COMPLETE_DEFER);
>>>>  
>>>>         /*
>>>> @@ -6456,12 +6465,16 @@ static void __io_queue_sqe(struct
>>>> io_kiocb *req)
>>>>                         io_put_req(req);
>>>>                 }
>>>>         } else if (ret == -EAGAIN && !(req->flags &
>>>> REQ_F_NOWAIT)) {
>>>> -               if (!io_arm_poll_handler(req)) {
>>>> +               switch (io_arm_poll_handler(req)) {
>>>> +               case IO_APOLL_READY:
>>>> +                       goto issue_sqe;
>>>> +               case IO_APOLL_ABORTED:
>>>>                         /*
>>>>                          * Queued up for async execution, worker
>>>> will release
>>>>                          * submit reference when the iocb is
>>>> actually submitted.
>>>>                          */
>>>>                         io_queue_async_work(req);
>>>> +                       break;
>>>
>>> Hmm, why there is a new break here? It will miscount
>>> @linked_timeout
>>> if you do that. Every io_prep_linked_timeout() should be matched
>>> with
>>> io_queue_linked_timeout().
>>
>> Never mind, I said some nonsense and apparently need some coffee
> 
> but this is a pertinant question, imho. I guess that you could get away

It appeared to me that it doesn't go down to the end of the function
but returns or so, that's the nonsense part.

> without it since it is the last case of the switch statement... I am
> not sure what kernel coding standard says about that.

breaks are preferable, and falling through should be explicitly
marked with fallthrough;
 
> However, I can tell you that there was also a break statement at the
> end of the case for IO_APOLL_READY and checkpatch.pl did complain about
> it saying that it was useless since it was following a goto statement.
> Therefore, I did remove that one.
> 
> checkpatch.pl did remain silent about the other remaining break. Hence
> this is why I left it there.

-- 
Pavel Begunkov

  reply	other threads:[~2021-06-22 20:51 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-22 12:17 [PATCH v4] io_uring: reduce latency by reissueing the operation Olivier Langlois
2021-06-22 17:54 ` Pavel Begunkov
2021-06-22 18:01   ` Pavel Begunkov
2021-06-22 19:05     ` Olivier Langlois
2021-06-22 20:51       ` Pavel Begunkov [this message]
2021-06-22 20:52 ` Pavel Begunkov
2021-06-25  0:45 ` Jens Axboe
2021-06-25  8:15   ` David Laight
2021-06-28  6:42     ` Olivier Langlois

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox