From e39c34dc8aeacacf082145abea7273e4871b2746 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Fri, 21 Dec 2018 14:47:34 -0700
Subject: [PATCH 1/1] t/aio-ring: update for continually rolling ring

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 t/aio-ring.c | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/t/aio-ring.c b/t/aio-ring.c
index c813c4e7..0d53b574 100644
--- a/t/aio-ring.c
+++ b/t/aio-ring.c
@@ -70,13 +70,15 @@ struct aio_cq_ring {
 #define IORING_FLAG_GETEVENTS	(1 << 1)
 
 #define DEPTH			32
-#define RING_SIZE		(DEPTH + 1)
 
 #define BATCH_SUBMIT		8
 #define BATCH_COMPLETE		8
 
 #define BS			4096
 
+static unsigned sq_ring_mask = DEPTH - 1;
+static unsigned cq_ring_mask = (2 * DEPTH) - 1;
+
 struct submitter {
 	pthread_t thread;
 	unsigned long max_blocks;
@@ -141,20 +143,18 @@ static void init_io(struct submitter *s, int fd, struct iocb *iocb)
 static int prep_more_ios(struct submitter *s, int fd, int max_ios)
 {
 	struct aio_sq_ring *ring = s->sq_ring;
-	u32 tail, next_tail, prepped = 0;
+	u32 index, tail, next_tail, prepped = 0;
 
 	next_tail = tail = ring->tail;
 	do {
 		next_tail++;
-		if (next_tail == ring->nr_events)
-			next_tail = 0;
-
 		barrier();
 		if (next_tail == ring->head)
 			break;
 
-		init_io(s, fd, &s->iocbs[tail]);
-		s->sq_ring->array[tail] = tail;
+		index = tail & sq_ring_mask;
+		init_io(s, fd, &s->iocbs[index]);
+		s->sq_ring->array[index] = index;
 		prepped++;
 		tail = next_tail;
 	} while (prepped < max_ios);
@@ -201,7 +201,7 @@ static int reap_events(struct submitter *s)
 		barrier();
 		if (head == ring->tail)
 			break;
-		ev = &ring->events[head];
+		ev = &ring->events[head & cq_ring_mask];
 		if (ev->res != BS) {
 			struct iocb *iocb = ev->obj;
 
@@ -215,8 +215,6 @@ static int reap_events(struct submitter *s)
 			s->cachemiss++;
 		reaped++;
 		head++;
-		if (head == ring->nr_events)
-			head = 0;
 	} while (1);
 
 	s->inflight -= reaped;
@@ -361,30 +359,30 @@ int main(int argc, char *argv[])
 
 	arm_sig_int();
 
-	size = sizeof(struct iocb) * RING_SIZE;
+	size = sizeof(struct iocb) * DEPTH;
 	if (posix_memalign(&p, 4096, size))
 		return 1;
 	memset(p, 0, size);
 	s->iocbs = p;
 
-	size = sizeof(struct aio_sq_ring) + RING_SIZE * sizeof(u32);
+	size = sizeof(struct aio_sq_ring) + DEPTH * sizeof(u32);
 	if (posix_memalign(&p, 4096, size))
 		return 1;
 	s->sq_ring = p;
 	memset(p, 0, size);
-	s->sq_ring->nr_events = RING_SIZE;
+	s->sq_ring->nr_events = DEPTH;
 	s->sq_ring->iocbs = (u64) s->iocbs;
 
 	/* CQ ring must be twice as big */
 	size = sizeof(struct aio_cq_ring) +
-			2 * RING_SIZE * sizeof(struct io_event);
+			2 * DEPTH * sizeof(struct io_event);
 	if (posix_memalign(&p, 4096, size))
 		return 1;
 	s->cq_ring = p;
 	memset(p, 0, size);
-	s->cq_ring->nr_events = 2 * RING_SIZE;
+	s->cq_ring->nr_events = 2 * DEPTH;
 
-	for (j = 0; j < RING_SIZE; j++) {
+	for (j = 0; j < DEPTH; j++) {
 		struct iocb *iocb = &s->iocbs[j];
 
 		if (posix_memalign(&iocb->u.c.buf, BS, BS)) {
@@ -406,7 +404,7 @@ int main(int argc, char *argv[])
 		s->sq_ring->sq_thread_cpu = sq_thread_cpu;
 	}
 
-	err = io_setup2(RING_SIZE, flags, s->sq_ring, s->cq_ring, &s->ioc);
+	err = io_setup2(DEPTH, flags, s->sq_ring, s->cq_ring, &s->ioc);
 	if (err) {
 		printf("ctx_init failed: %s, %d\n", strerror(errno), err);
 		return 1;
-- 
2.25.1