From: Xiaoguang Wang <[email protected]>
To: Jens Axboe <[email protected]>,
[email protected], [email protected]
Cc: Liming Wu <[email protected]>
Subject: Re: [PATCH] io_uring:IORING_SETUP_SQPOLL don't need to enter io_cqring_wait
Date: Wed, 8 Apr 2020 13:30:35 +0800 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
hi,
> On 4/7/20 1:44 AM, [email protected] wrote:
>> From: Liming Wu <[email protected]>
>>
>> When SETUP_IOPOLL and SETUP_SQPOLL are both enabled, app don't
>> need to enter io_cqring_wait too. If I misunderstand, please give
>> me some advise.
>
> The logic should be as follows:
>
> flags method
> ---------------------------------------------
> 0 io_cqring_wait()
> IOPOLL io_iopoll_check()
> IOPOLL | SQPOLL io_cqring_wait()
> SQPOLL io_cqring_wait()
>
> The reasoning being that we do want to enter cqring_wait() for SQPOLL,
> as the application may want to wait for completions. Even with IOPOLL
> set. As far as I can tell, the current code is correct, as long as we
> know SQPOLL will always poll for events for us.
Yes, agree.
Regards,
Xiaoguang Wang
>
> So I'm curious why you think your patch is needed? Leaving it below and
> CC'ing Xiaoguang, who made the most recent change, so he can comment.
>
>> Signed-off-by Liming Wu <[email protected]>
>> ---
>> io_uring.c | 11 ++++++-----
>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/io_uring.c b/io_uring.c
>> index b12d33b..36e884f 100644
>> --- a/io_uring.c
>> +++ b/io_uring.c
>> @@ -7418,11 +7418,12 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
>> * polling again, they can rely on io_sq_thread to do polling
>> * work, which can reduce cpu usage and uring_lock contention.
>> */
>> - if (ctx->flags & IORING_SETUP_IOPOLL &&
>> - !(ctx->flags & IORING_SETUP_SQPOLL)) {
>> - ret = io_iopoll_check(ctx, &nr_events, min_complete);
>> - } else {
>> - ret = io_cqring_wait(ctx, min_complete, sig, sigsz);
>> + if (!(ctx->flags & IORING_SETUP_SQPOLL)) {
>> + if (ctx->flags & IORING_SETUP_IOPOLL) {
>> + ret = io_iopoll_check(ctx, &nr_events, min_complete);
>> + } else {
>> + ret = io_cqring_wait(ctx, min_complete, sig, sigsz);
>> + }
>> }
>> }
>>
>>
>
>
next prev parent reply other threads:[~2020-04-08 5:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-07 8:44 [PATCH] io_uring:IORING_SETUP_SQPOLL don't need to enter io_cqring_wait wu860403
2020-04-07 22:04 ` Jens Axboe
2020-04-08 5:30 ` Xiaoguang Wang [this message]
2020-04-08 5:43 ` Xiaoguang Wang
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