6.4-stable patches

added patches:
	io_uring-use-io_schedule-in-cqring-wait.patch

diff --git a/queue-6.4/io_uring-use-io_schedule-in-cqring-wait.patch b/queue-6.4/io_uring-use-io_schedule-in-cqring-wait.patch
new file mode 100644 (file)
index 0000000..12d0dff
--- /dev/null
+++ b/queue-6.4/io_uring-use-io_schedule-in-cqring-wait.patch
@@ -0,0 +1,81 @@
+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: io_uring: Use io_schedule* in cqring wait
+
+From: Andres Freund <andres@anarazel.de>
+
+commit 8a796565cec3601071cbbd27d6304e202019d014 upstream.
+
+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>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ io_uring/io_uring.c |   15 +++++++++++++--
+ 1 file changed, 13 insertions(+), 2 deletions(-)
+
+--- a/io_uring/io_uring.c
++++ b/io_uring/io_uring.c
+@@ -2575,6 +2575,8 @@ int io_run_task_work_sig(struct io_ring_
+ 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)))
+@@ -2585,11 +2587,20 @@ static inline int io_cqring_wait_schedul
+               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;
+ }
+ 
+ /*

diff --git a/queue-6.4/series b/queue-6.4/series
index beeaeefa68f8b6ddd551926ca91a3ae541d9f42a..e07f88dac4bdb4ad09eb730a06c510c2a21a07f5 100644 (file)
--- a/queue-6.4/series
+++ b/queue-6.4/series
@@ -715,3 +715,4 @@ i2c-xiic-don-t-try-to-handle-more-interrupt-events-a.patch
 writeback-account-the-number-of-pages-written-back.patch
 lib-dhry-fix-sleeping-allocations-inside-non-preempt.patch
 revert-drm-amd-display-move-dcn314-domain-power-cont.patch
+io_uring-use-io_schedule-in-cqring-wait.patch