From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 1 Sep 2022 14:34:32 +0000 (-0600)
Subject: t/io_uring: minor optimizations to IO init fast path
X-Git-Tag: fio-3.33~52
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=6b6f52b9b74219d5d7c93e61d21250bb47ecfe66

t/io_uring: minor optimizations to IO init fast path

1) Only read SQ ring head at the start of prep, we don't need to read
   it at every iteration.
2) Initialize SQ ring index at init time, rather than in the fast path.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/t/io_uring.c b/t/io_uring.c
index 5b46015a..9d580b5a 100644
--- a/t/io_uring.c
+++ b/t/io_uring.c
@@ -658,11 +658,12 @@ static int prep_more_ios_uring(struct submitter *s, int max_ios)
 {
 	struct io_sq_ring *ring = &s->sq_ring;
 	unsigned index, tail, next_tail, prepped = 0;
+	unsigned int head = atomic_load_acquire(ring->head);
 
 	next_tail = tail = *ring->tail;
 	do {
 		next_tail++;
-		if (next_tail == atomic_load_acquire(ring->head))
+		if (next_tail == head)
 			break;
 
 		index = tail & sq_ring_mask;
@@ -670,7 +671,6 @@ static int prep_more_ios_uring(struct submitter *s, int max_ios)
 			init_io_pt(s, index);
 		else
 			init_io(s, index);
-		ring->array[index] = index;
 		prepped++;
 		tail = next_tail;
 	} while (prepped < max_ios);
@@ -908,7 +908,7 @@ static int setup_ring(struct submitter *s)
 	struct io_sq_ring *sring = &s->sq_ring;
 	struct io_cq_ring *cring = &s->cq_ring;
 	struct io_uring_params p;
-	int ret, fd;
+	int ret, fd, i;
 	void *ptr;
 	size_t len;
 
@@ -1003,6 +1003,10 @@ static int setup_ring(struct submitter *s)
 	cring->ring_entries = ptr + p.cq_off.ring_entries;
 	cring->cqes = ptr + p.cq_off.cqes;
 	cq_ring_mask = *cring->ring_mask;
+
+	for (i = 0; i < p.sq_entries; i++)
+		sring->array[i] = i;
+
 	return 0;
 }