public inbox for [email protected]
 help / color / mirror / Atom feed
From: Jens Axboe <[email protected]>
To: [email protected]
Cc: [email protected], [email protected], Jens Axboe <[email protected]>
Subject: [PATCH 2/2] io_uring: include task_work run after scheduling in wait for events
Date: Sat, 17 Dec 2022 13:48:40 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

It's quite possible that we got woken up because task_work was queued,
and we need to process this task_work to generate the events waited for.
If we return to the wait loop without running task_work, we'll end up
adding the task to the waitqueue again, only to call
io_cqring_wait_schedule() again which will run the task_work. This is
less efficient than it could be, as it requires adding to the cq_wait
queue again. It also triggers the wakeup path for completions as
cq_wait is now non-empty with the task itself, and it'll require another
lock grab and deletion to remove ourselves from the waitqueue.

Signed-off-by: Jens Axboe <[email protected]>
---
 io_uring/io_uring.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 16a323a9ff70..945bea3e8e5f 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2481,7 +2481,7 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 	}
 	if (!schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS))
 		return -ETIME;
-	return 1;
+	return io_run_task_work_sig(ctx);
 }
 
 /*
@@ -2546,6 +2546,8 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 		prepare_to_wait_exclusive(&ctx->cq_wait, &iowq.wq,
 						TASK_INTERRUPTIBLE);
 		ret = io_cqring_wait_schedule(ctx, &iowq, timeout);
+		if (__io_cqring_events_user(ctx) >= min_events)
+			break;
 		cond_resched();
 	} while (ret > 0);
 
-- 
2.35.1


  parent reply	other threads:[~2022-12-17 20:49 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-17 20:48 [PATCHSET 0/2] tw/wakeup tweaks Jens Axboe
2022-12-17 20:48 ` [PATCH 1/2] io_uring: don't use TIF_NOTIFY_SIGNAL to test for availability of task_work Jens Axboe
2022-12-17 20:48 ` Jens Axboe [this message]
2022-12-18  3:37   ` [PATCH v2 2/2] io_uring: include task_work run after scheduling in wait for events Jens Axboe

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] \
    /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