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 5b46015aa394175bb9167cf02e95a9cc8ccf2f6a..9d580b5af11b529af3233298547f8ed051ae88d7 100644 (file)
--- 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;
 }