net/virtio: restrict pointer aliasing for NEON

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

With this patch, a 9.6% improvement is observed in throughput for
the virtio-net PVP case, and a 2.4% perf improvement in throughput
for the virtio-user PVP case. All performance data are measured
on ThunderX-2 platform under the 0.001% acceptable packet loss with
2 cores on the vhost side and 1 core on the virtio side.

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

diff --git a/drivers/net/virtio/virtio_rxtx_simple_neon.c b/drivers/net/virtio/virtio_rxtx_simple_neon.c
index 8e6fa1f..a9b6498 100644 (file)
--- a/drivers/net/virtio/virtio_rxtx_simple_neon.c
+++ b/drivers/net/virtio/virtio_rxtx_simple_neon.c
@@ -36,8 +36,8 @@
  * - nb_pkts < RTE_VIRTIO_DESC_PER_LOOP, just return no packet
  */
 uint16_t
-virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **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;