FAILED: patch "[PATCH] io_uring: Use io_schedule* in cqring wait" failed to apply to 5.10-stable tree

FAILED: patch "[PATCH] io_uring: Use io_schedule* in cqring wait" failed to apply to 5.10-stable tree

[gregkh]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 8a796565cec3601071cbbd27d6304e202019d014
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023071623-deafness-gargle-5297@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

8a796565cec3 ("io_uring: Use io_schedule* in cqring wait")
d33a39e57768 ("io_uring: keep timeout in io_wait_queue")
46ae7eef44f6 ("io_uring: optimise non-timeout waiting")
846072f16eed ("io_uring: mimimise io_cqring_wait_schedule")
3fcf19d592d5 ("io_uring: parse check_cq out of wq waiting")
12521a5d5cb7 ("io_uring: fix CQ waiting timeout handling")
52ea806ad983 ("io_uring: finish waiting before flushing overflow entries")
35d90f95cfa7 ("io_uring: include task_work run after scheduling in wait for events")
1b346e4aa8e7 ("io_uring: don't check overflow flush failures")
a85381d8326d ("io_uring: skip overflow CQE posting for dying ring")
c0e0d6ba25f1 ("io_uring: add IORING_SETUP_DEFER_TASKRUN")
b4c98d59a787 ("io_uring: introduce io_has_work")
78a861b94959 ("io_uring: add sync cancelation API through io_uring_register()")
c34398a8c018 ("io_uring: remove __io_req_task_work_add")
ed5ccb3beeba ("io_uring: remove priority tw list optimisation")
4a0fef62788b ("io_uring: optimize io_uring_task layout")
253993210bd8 ("io_uring: introduce locking helpers for CQE posting")
305bef988708 ("io_uring: hide eventfd assumptions in eventfd paths")
affa87db9010 ("io_uring: fix multi ctx cancellation")
d9dee4302a7c ("io_uring: remove ->flush_cqes optimisation")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8a796565cec3601071cbbd27d6304e202019d014 Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Fri, 7 Jul 2023 09:20:07 -0700
Subject: [PATCH] io_uring: Use io_schedule* in cqring wait

I observed poor performance of io_uring compared to synchronous IO. That
turns out to be caused by deeper CPU idle states entered with io_uring,
due to io_uring using plain schedule(), whereas synchronous IO uses
io_schedule().

The losses due to this are substantial. On my cascade lake workstation,
t/io_uring from the fio repository e.g. yields regressions between 20%
and 40% with the following command:
./t/io_uring -r 5 -X0 -d 1 -s 1 -c 1 -p 0 -S$use_sync -R 0 /mnt/t2/fio/write.0.0

This is repeatable with different filesystems, using raw block devices
and using different block devices.

Use io_schedule_prepare() / io_schedule_finish() in
io_cqring_wait_schedule() to address the difference.

After that using io_uring is on par or surpassing synchronous IO (using
registered files etc makes it reliably win, but arguably is a less fair
comparison).

There are other calls to schedule() in io_uring/, but none immediately
jump out to be similarly situated, so I did not touch them. Similarly,
it's possible that mutex_lock_io() should be used, but it's not clear if
there are cases where that matters.

Cc: stable@vger.kernel.org # 5.10+
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: io-uring@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Andres Freund <andres@anarazel.de>
Link: https://lore.kernel.org/r/20230707162007.194068-1-andres@anarazel.de
[axboe: minor style fixup]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index e8096d502a7c..7505de2428e0 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2489,6 +2489,8 @@ int io_run_task_work_sig(struct io_ring_ctx *ctx)
 static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 					  struct io_wait_queue *iowq)
 {
+	int token, ret;
+
 	if (unlikely(READ_ONCE(ctx->check_cq)))
 		return 1;
 	if (unlikely(!llist_empty(&ctx->work_llist)))
@@ -2499,11 +2501,20 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 		return -EINTR;
 	if (unlikely(io_should_wake(iowq)))
 		return 0;
+
+	/*
+	 * Use io_schedule_prepare/finish, so cpufreq can take into account
+	 * that the task is waiting for IO - turns out to be important for low
+	 * QD IO.
+	 */
+	token = io_schedule_prepare();
+	ret = 0;
 	if (iowq->timeout == KTIME_MAX)
 		schedule();
 	else if (!schedule_hrtimeout(&iowq->timeout, HRTIMER_MODE_ABS))
-		return -ETIME;
-	return 0;
+		ret = -ETIME;
+	io_schedule_finish(token);
+	return ret;
 }
 
 /*

Re: FAILED: patch "[PATCH] io_uring: Use io_schedule* in cqring wait" failed to apply to 5.10-stable tree

[Jens Axboe]

[-- Attachment #1: Type: text/plain, Size: 825 bytes --]

On 7/16/23 2:41 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 5.10-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> To reproduce the conflict and resubmit, you may use the following commands:
> 
> git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
> git checkout FETCH_HEAD
> git cherry-pick -x 8a796565cec3601071cbbd27d6304e202019d014
> # <resolve conflicts, build, test, etc.>
> git commit -s
> git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023071623-deafness-gargle-5297@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Here's one for 5.10-stable and 5.15-stable.

-- 
Jens Axboe


[-- Attachment #2: 0001-io_uring-Use-io_schedule-in-cqring-wait.patch --]
[-- Type: text/x-patch, Size: 2707 bytes --]

From bc9ba1116c57882d7539af60adb1ee329c46b556 Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Sun, 16 Jul 2023 12:07:03 -0600
Subject: [PATCH] io_uring: Use io_schedule* in cqring wait

I observed poor performance of io_uring compared to synchronous IO. That
turns out to be caused by deeper CPU idle states entered with io_uring,
due to io_uring using plain schedule(), whereas synchronous IO uses
io_schedule().

The losses due to this are substantial. On my cascade lake workstation,
t/io_uring from the fio repository e.g. yields regressions between 20%
and 40% with the following command:
./t/io_uring -r 5 -X0 -d 1 -s 1 -c 1 -p 0 -S$use_sync -R 0 /mnt/t2/fio/write.0.0

This is repeatable with different filesystems, using raw block devices
and using different block devices.

Use io_schedule_prepare() / io_schedule_finish() in
io_cqring_wait_schedule() to address the difference.

After that using io_uring is on par or surpassing synchronous IO (using
registered files etc makes it reliably win, but arguably is a less fair
comparison).

There are other calls to schedule() in io_uring/, but none immediately
jump out to be similarly situated, so I did not touch them. Similarly,
it's possible that mutex_lock_io() should be used, but it's not clear if
there are cases where that matters.

Cc: stable@vger.kernel.org # 5.10+
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: io-uring@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Andres Freund <andres@anarazel.de>
Link: https://lore.kernel.org/r/20230707162007.194068-1-andres@anarazel.de
[axboe: minor style fixup]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/io_uring.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index e633799c9cea..010cc06df4e9 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -7785,7 +7785,7 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 					  struct io_wait_queue *iowq,
 					  ktime_t *timeout)
 {
-	int ret;
+	int token, ret;
 
 	/* make sure we run task_work before checking for signals */
 	ret = io_run_task_work_sig();
@@ -7795,9 +7795,17 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 	if (test_bit(0, &ctx->check_cq_overflow))
 		return 1;
 
+	/*
+	 * Use io_schedule_prepare/finish, so cpufreq can take into account
+	 * that the task is waiting for IO - turns out to be important for low
+	 * QD IO.
+	 */
+	token = io_schedule_prepare();
+	ret = 0;
 	if (!schedule_hrtimeout(timeout, HRTIMER_MODE_ABS))
-		return -ETIME;
-	return 1;
+		ret = -ETIME;
+	io_schedule_finish(token);
+	return ret;
 }
 
 /*
-- 
2.40.1

Re: FAILED: patch "[PATCH] io_uring: Use io_schedule* in cqring wait" failed to apply to 5.10-stable tree

[Greg KH]

On Sun, Jul 16, 2023 at 12:08:11PM -0600, Jens Axboe wrote:
> On 7/16/23 2:41 AM, gregkh@linuxfoundation.org wrote:
> > 
> > The patch below does not apply to the 5.10-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
> > 
> > To reproduce the conflict and resubmit, you may use the following commands:
> > 
> > git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
> > git checkout FETCH_HEAD
> > git cherry-pick -x 8a796565cec3601071cbbd27d6304e202019d014
> > # <resolve conflicts, build, test, etc.>
> > git commit -s
> > git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023071623-deafness-gargle-5297@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..
> 
> Here's one for 5.10-stable and 5.15-stable.

All now queued up, thanks!

greg k-h