virtio: optimize avail ring update

[dpdk.git] / drivers / net / virtio / virtqueue.h

diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 4e9239e..8c46a83 100644 (file)
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -302,7 +302,8 @@ vq_update_avail_ring(struct virtqueue *vq, uint16_t desc_idx)
         * descriptor.
         */
        avail_idx = (uint16_t)(vq->vq_avail_idx & (vq->vq_nentries - 1));
-       vq->vq_ring.avail->ring[avail_idx] = desc_idx;
+       if (unlikely(vq->vq_ring.avail->ring[avail_idx] != desc_idx))
+               vq->vq_ring.avail->ring[avail_idx] = desc_idx;
        vq->vq_avail_idx++;
 }