From 90291099f24a82863e00de136d95ad7e73560107 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Mon, 9 Aug 2021 09:07:32 -0600 Subject: [PATCH] io_uring: optimise io_cqring_wait() hot path Turns out we always init struct io_wait_queue in io_cqring_wait(), even if it's not used after, i.e. there are already enough of CQEs. And often it's exactly what happens, for instance, requests may have been completed inline, or in case of io_uring_enter(submit=N, wait=1). It shows up in my profiler, so optimise it by delaying the struct init. Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/r/6f1b81c60b947d165583dc333947869c3d85d037.1628471125.git.asml.silence@gmail.com [axboe: fixed up for new cqring wait] Signed-off-by: Jens Axboe --- fs/io_uring.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index ff17c4e9aa425..14aaeb87b149b 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -7063,14 +7063,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, const sigset_t __user *sig, size_t sigsz, struct __kernel_timespec __user *uts) { - struct io_wait_queue iowq = { - .wq = { - .private = current, - .func = io_wake_function, - .entry = LIST_HEAD_INIT(iowq.wq.entry), - }, - .ctx = ctx, - }; + struct io_wait_queue iowq; struct io_rings *rings = ctx->rings; signed long timeout = MAX_SCHEDULE_TIMEOUT; int ret; @@ -7104,8 +7097,13 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, timeout = timespec64_to_jiffies(&ts); } + init_waitqueue_func_entry(&iowq.wq, io_wake_function); + iowq.wq.private = current; + INIT_LIST_HEAD(&iowq.wq.entry); + iowq.ctx = ctx; iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts); iowq.cq_tail = READ_ONCE(ctx->rings->cq.head) + min_events; + trace_io_uring_cqring_wait(ctx, min_events); do { /* if we can't even flush overflow, don't wait for more */ -- 2.30.2