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io_uring: remove extra barrier for non-sqpoll iopoll

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smp_mb() in io_cqring_ev_posted_iopoll() is only there because of
waitqueue_active(). However, non-SQPOLL IOPOLL ring doesn't wake the CQ
and so the barrier there is useless. Kill it, it's usually pretty
expensive.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d72e8ef6f7a3f6a72e18fad8409f7d47afc8da7d.1647481208.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2022-03-17 02:03:39 +00:00 committed by Jens Axboe
parent b91ef18728
commit 0f84747177
1 changed files with 1 additions and 4 deletions
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5
fs/io_uring.c
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@ -1877,11 +1877,8 @@ static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
{
/* see waitqueue_active() comment */
smp_mb();
if (ctx->flags & IORING_SETUP_SQPOLL) {
if (waitqueue_active(&ctx->cq_wait))
if (wq_has_sleeper(&ctx->cq_wait))
wake_up_all(&ctx->cq_wait);
}
io_eventfd_signal(ctx);