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From: Pavel Begunkov <[email protected]>
To: [email protected]
Cc: Jens Axboe <[email protected]>, [email protected]
Subject: [RFC v2 05/13] io_uring: parse check_cq out of wq waiting
Date: Tue,  3 Jan 2023 03:03:56 +0000	[thread overview]
Message-ID: <e28cb002457c26c6159de4d80e7c437fe13711b5.1672713341.git.asml.silence@gmail.com> (raw)
In-Reply-To: <[email protected]>

We already avoid flushing overflows in io_cqring_wait_schedule() but
only return an error for the outer loop to handle it. Minimise it even
further by moving all ->check_cq parsing there.

Signed-off-by: Pavel Begunkov <[email protected]>
---
 io_uring/io_uring.c | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index ff457e525e7c..e3c5de299baa 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2468,21 +2468,13 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 					  ktime_t timeout)
 {
 	int ret;
-	unsigned long check_cq;
 
+	if (unlikely(READ_ONCE(ctx->check_cq)))
+		return 1;
 	/* make sure we run task_work before checking for signals */
 	ret = io_run_task_work_sig(ctx);
 	if (ret || io_should_wake(iowq))
 		return ret;
-
-	check_cq = READ_ONCE(ctx->check_cq);
-	if (unlikely(check_cq)) {
-		/* let the caller flush overflows, retry */
-		if (check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT))
-			return 1;
-		if (check_cq & BIT(IO_CHECK_CQ_DROPPED_BIT))
-			return -EBADR;
-	}
 	if (!schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS))
 		return -ETIME;
 
@@ -2548,13 +2540,25 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 
 	trace_io_uring_cqring_wait(ctx, min_events);
 	do {
-		if (test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq)) {
-			finish_wait(&ctx->cq_wait, &iowq.wq);
-			io_cqring_do_overflow_flush(ctx);
-		}
+		unsigned long check_cq;
+
 		prepare_to_wait_exclusive(&ctx->cq_wait, &iowq.wq,
 						TASK_INTERRUPTIBLE);
 		ret = io_cqring_wait_schedule(ctx, &iowq, timeout);
+
+		check_cq = READ_ONCE(ctx->check_cq);
+		if (unlikely(check_cq)) {
+			/* let the caller flush overflows, retry */
+			if (check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT)) {
+				finish_wait(&ctx->cq_wait, &iowq.wq);
+				io_cqring_do_overflow_flush(ctx);
+			}
+			if (check_cq & BIT(IO_CHECK_CQ_DROPPED_BIT)) {
+				ret = -EBADR;
+				break;
+			}
+		}
+
 		if (__io_cqring_events_user(ctx) >= min_events)
 			break;
 		cond_resched();
-- 
2.38.1


  parent reply	other threads:[~2023-01-03  3:05 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-03  3:03 [RFC v2 00/13] CQ waiting and wake up optimisations Pavel Begunkov
2023-01-03  3:03 ` [RFC v2 01/13] io_uring: rearrange defer list checks Pavel Begunkov
2023-01-03  3:03 ` [RFC v2 02/13] io_uring: don't iterate cq wait fast path Pavel Begunkov
2023-01-03  3:03 ` [RFC v2 03/13] io_uring: kill io_run_task_work_ctx Pavel Begunkov
2023-01-03  3:03 ` [RFC v2 04/13] io_uring: move defer tw task checks Pavel Begunkov
2023-01-03  3:03 ` Pavel Begunkov [this message]
2023-01-03  3:03 ` [RFC v2 06/13] io_uring: mimimise io_cqring_wait_schedule Pavel Begunkov
2023-01-03  3:03 ` [RFC v2 07/13] io_uring: simplify io_has_work Pavel Begunkov
2023-01-03  3:03 ` [RFC v2 08/13] io_uring: set TASK_RUNNING right after schedule Pavel Begunkov
2023-01-03  3:04 ` [RFC v2 09/13] io_uring: separate wq for ring polling Pavel Begunkov
2023-01-04 18:08   ` Jens Axboe
2023-01-04 20:28     ` Pavel Begunkov
2023-01-04 20:34       ` Jens Axboe
2023-01-04 20:45         ` Pavel Begunkov
2023-01-04 20:53           ` Jens Axboe
2023-01-04 20:52         ` Jens Axboe
2023-01-03  3:04 ` [RFC v2 10/13] io_uring: add lazy poll_wq activation Pavel Begunkov
2023-01-03  3:04 ` [RFC v2 11/13] io_uring: wake up optimisations Pavel Begunkov
2023-01-03  3:04 ` [RFC v2 12/13] io_uring: waitqueue-less cq waiting Pavel Begunkov
2023-01-03  3:04 ` [RFC v2 13/13] io_uring: add io_req_local_work_add wake fast path Pavel Begunkov
2023-01-04 18:05 ` (subset) [RFC v2 00/13] CQ waiting and wake up optimisations Jens Axboe
2023-01-04 20:25 ` Pavel Begunkov

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