On 7/16/23 12:13 PM, Jens Axboe wrote: > On 7/16/23 2:41 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote: >> >> The patch below does not apply to the 6.1-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@xxxxxxxxxxxxxxx>. >> >> 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-6.1.y >> git checkout FETCH_HEAD >> git cherry-pick -x 8a796565cec3601071cbbd27d6304e202019d014 >> # <resolve conflicts, build, test, etc.> >> git commit -s >> git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023071620-litigate-debunk-939a@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. > > Here's one for 6.1-stable. And here's a corrected one for 6.1. -- Jens Axboe
From f5f24ec27340daf12177fd09c2d107a589cbf527 Mon Sep 17 00:00:00 2001 From: Andres Freund <andres@xxxxxxxxxxx> Date: Sun, 16 Jul 2023 12:13:06 -0600 Subject: [PATCH] io_uring: Use io_schedule* in cqring wait 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@xxxxxxxxxxxxxxx # 5.10+ Cc: Pavel Begunkov <asml.silence@xxxxxxxxx> Cc: io-uring@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Andres Freund <andres@xxxxxxxxxxx> Link: https://lore.kernel.org/r/20230707162007.194068-1-andres@xxxxxxxxxxx [axboe: minor style fixup] Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- io_uring/io_uring.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index cc35aba1e495..6d7b358e71f1 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2346,7 +2346,7 @@ 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; unsigned long check_cq; /* make sure we run task_work before checking for signals */ @@ -2362,9 +2362,18 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx, if (check_cq & BIT(IO_CHECK_CQ_DROPPED_BIT)) return -EBADR; } + + /* + * 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 = 1; if (!schedule_hrtimeout(timeout, HRTIMER_MODE_ABS)) - return -ETIME; - return 1; + ret = -ETIME; + io_schedule_finish(token); + return ret; } /* -- 2.40.1
