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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);
>> +		    }
>>   		}
>>   	}
>>   
>>
> 
> 

  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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