syslet: make sure ring buffer is a power-of-2

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/engines/syslet-rw.c b/engines/syslet-rw.c
index d74fcdf86e3d6f021c31915b169d91eb8acea70c..2e23fc937fee6fca810c694f0dfa7f96563bbb4d 100644 (file)
--- a/engines/syslet-rw.c
+++ b/engines/syslet-rw.c
@@ -225,13 +225,30 @@ static int fio_syslet_init(struct thread_data *td)
 {
        struct syslet_data *sd;
        void *ring = NULL, *stack = NULL;
+       unsigned int ring_size, ring_nr;
 
        sd = malloc(sizeof(*sd));
        memset(sd, 0, sizeof(*sd));
 
        sd->events = malloc(sizeof(struct io_u *) * td->o.iodepth);
        memset(sd->events, 0, sizeof(struct io_u *) * td->o.iodepth);
-       if (posix_memalign(&ring, sizeof(uint64_t), sizeof(struct syslet_ring)))
+
+       /*
+        * The ring needs to be a power-of-2, so round it up if we have to
+        */
+       ring_nr = td->o.iodepth;
+       if (ring_nr & (ring_nr - 1)) {
+               int bits = 1;
+
+               while (ring_nr >>= 1)
+                       bits++;
+
+               ring_nr = 1 << bits;
+       }
+
+       ring_size = sizeof(struct syslet_ring) +
+                       ring_nr * sizeof(struct syslet_completion);
+       if (posix_memalign(&ring, sizeof(uint64_t), ring_size))
                goto err_mem;
        if (posix_memalign(&stack, page_size, page_size))
                goto err_mem;
@@ -239,8 +256,8 @@ static int fio_syslet_init(struct thread_data *td)
        sd->ring = ring;
        sd->stack = stack;
 
-       memset(sd->ring, 0, sizeof(*sd->ring));
-       sd->ring->elements = td->o.iodepth;
+       memset(sd->ring, 0, ring_size);
+       sd->ring->elements = ring_nr;
 
        if (!check_syslet_support(sd)) {
                td->io_ops->data = sd;