vhost: restrict pointer aliasing for packed ring

Restrict pointer aliasing to allow the compiler to vectorize loop
more aggressively.

With this patch, a 9.6% improvement is observed in throughput for
the packed virtio-net PVP case, and a 2.8% improvement in throughput
for the packed virtio-user PVP case. All performance data are measured
on ThunderX-2 platform under 0.001% acceptable packet loss with 1 core
on both vhost and virtio side.

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
Acked-by: Adrián Moreno <amorenoz@redhat.com>

diff --git a/drivers/net/virtio/virtio_rxtx_simple_neon.c b/drivers/net/virtio/virtio_rxtx_simple_neon.c
index a9b6498..02520fd 100644 (file)
--- a/drivers/net/virtio/virtio_rxtx_simple_neon.c
+++ b/drivers/net/virtio/virtio_rxtx_simple_neon.c
@@ -36,8 +36,9 @@
  * - nb_pkts < RTE_VIRTIO_DESC_PER_LOOP, just return no packet
  */
 uint16_t
-virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf
-               **__rte_restrict rx_pkts, uint16_t nb_pkts)
+virtio_recv_pkts_vec(void *rx_queue,
+               struct rte_mbuf **__rte_restrict rx_pkts,
+               uint16_t nb_pkts)
 {
        struct virtnet_rx *rxvq = rx_queue;
        struct virtqueue *vq = rxvq->vq;

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 236498f..1d0be3d 100644 (file)
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -1353,8 +1353,8 @@ virtio_dev_rx_single_packed(struct virtio_net *dev,
 
 static __rte_noinline uint32_t
 virtio_dev_rx_packed(struct virtio_net *dev,
-                    struct vhost_virtqueue *vq,
-                    struct rte_mbuf **pkts,
+                    struct vhost_virtqueue *__rte_restrict vq,
+                    struct rte_mbuf **__rte_restrict pkts,
                     uint32_t count)
 {
        uint32_t pkt_idx = 0;
@@ -1439,7 +1439,7 @@ out_access_unlock:
 
 uint16_t
 rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
-       struct rte_mbuf **pkts, uint16_t count)
+       struct rte_mbuf **__rte_restrict pkts, uint16_t count)
 {
        struct virtio_net *dev = get_device(vid);
 
@@ -2671,9 +2671,9 @@ free_zmbuf(struct vhost_virtqueue *vq)
 
 static __rte_noinline uint16_t
 virtio_dev_tx_packed_zmbuf(struct virtio_net *dev,
-                          struct vhost_virtqueue *vq,
+                          struct vhost_virtqueue *__rte_restrict vq,
                           struct rte_mempool *mbuf_pool,
-                          struct rte_mbuf **pkts,
+                          struct rte_mbuf **__rte_restrict pkts,
                           uint32_t count)
 {
        uint32_t pkt_idx = 0;
@@ -2707,9 +2707,9 @@ virtio_dev_tx_packed_zmbuf(struct virtio_net *dev,
 
 static __rte_noinline uint16_t
 virtio_dev_tx_packed(struct virtio_net *dev,
-                    struct vhost_virtqueue *vq,
+                    struct vhost_virtqueue *__rte_restrict vq,
                     struct rte_mempool *mbuf_pool,
-                    struct rte_mbuf **pkts,
+                    struct rte_mbuf **__rte_restrict pkts,
                     uint32_t count)
 {
        uint32_t pkt_idx = 0;