Re: [PATCH for-next 2/2] io_uring: optimise ltimeout for inline execution

[Pavel Begunkov <asml.silence@gmail.com>]

On 12/1/23 00:38, Pavel Begunkov wrote:
> At one point in time we had an optimisation that would not spin up a
> linked timeout timer when the master request successfully completes
> inline (during the first nowait execution attempt). We somehow lost it,
> so this patch restores it back.
> 
> Note, that it's fine using io_arm_ltimeout() after the io_issue_sqe()
> completes the request because of delayed completion, but that that adds
> unwanted overhead.

Let's add:

Reported-by: Christian Mazakas <christian.mazakas@gmail.com>

> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>   io_uring/io_uring.c | 19 +++++++++----------
>   1 file changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 21e646ef9654..6212f81ed887 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -1900,14 +1900,15 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
>   		return 0;
>   	}
>   
> -	if (ret != IOU_ISSUE_SKIP_COMPLETE)
> -		return ret;
> -
> -	/* If the op doesn't have a file, we're not polling for it */
> -	if ((req->ctx->flags & IORING_SETUP_IOPOLL) && def->iopoll_queue)
> -		io_iopoll_req_issued(req, issue_flags);
> +	if (ret == IOU_ISSUE_SKIP_COMPLETE) {
> +		ret = 0;
> +		io_arm_ltimeout(req);
>   
> -	return 0;
> +		/* If the op doesn't have a file, we're not polling for it */
> +		if ((req->ctx->flags & IORING_SETUP_IOPOLL) && def->iopoll_queue)
> +			io_iopoll_req_issued(req, issue_flags);
> +	}
> +	return ret;
>   }
>   
>   int io_poll_issue(struct io_kiocb *req, struct io_tw_state *ts)
> @@ -2078,9 +2079,7 @@ static inline void io_queue_sqe(struct io_kiocb *req)
>   	 * We async punt it if the file wasn't marked NOWAIT, or if the file
>   	 * doesn't support non-blocking read/write attempts
>   	 */
> -	if (likely(!ret))
> -		io_arm_ltimeout(req);
> -	else
> +	if (unlikely(ret))
>   		io_queue_async(req, ret);
>   }
>   

-- 
Pavel Begunkov