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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> |
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| .. | ||
| advise.c | ||
| advise.h | ||
| alloc_cache.h | ||
| cancel.c | ||
| cancel.h | ||
| epoll.c | ||
| epoll.h | ||
| fdinfo.c | ||
| fdinfo.h | ||
| filetable.c | ||
| filetable.h | ||
| fs.c | ||
| fs.h | ||
| io_uring.c | ||
| io_uring.h | ||
| io-wq.c | ||
| io-wq.h | ||
| kbuf.c | ||
| kbuf.h | ||
| Makefile | ||
| msg_ring.c | ||
| msg_ring.h | ||
| net.c | ||
| net.h | ||
| nop.c | ||
| nop.h | ||
| notif.c | ||
| notif.h | ||
| opdef.c | ||
| opdef.h | ||
| openclose.c | ||
| openclose.h | ||
| poll.c | ||
| poll.h | ||
| refs.h | ||
| rsrc.c | ||
| rsrc.h | ||
| rw.c | ||
| rw.h | ||
| slist.h | ||
| splice.c | ||
| splice.h | ||
| sqpoll.c | ||
| sqpoll.h | ||
| statx.c | ||
| statx.h | ||
| sync.c | ||
| sync.h | ||
| tctx.c | ||
| tctx.h | ||
| timeout.c | ||
| timeout.h | ||
| uring_cmd.c | ||
| uring_cmd.h | ||
| xattr.c | ||
| xattr.h | ||