X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;ds=sidebyside;f=lib%2Flibrte_vhost%2Fvirtio_net.c;h=ea027f1405777347ab2fb7280a4c7dc3abf39415;hb=9365d6cfd641d5ade83591c5f5dfa2bf32808e4e;hp=337470d64ad3875722e3934a940c217890e20dea;hpb=98b330d5d42b569850026263bbda81511c583252;p=deb_dpdk.git

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 337470d6..ea027f14 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -905,6 +905,8 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vring_desc *descs,
 					"allocate memory for mbuf.\n");
 				return -1;
 			}
+			if (unlikely(dev->dequeue_zero_copy))
+				rte_mbuf_refcnt_update(cur, 1);
 
 			prev->next = cur;
 			prev->data_len = mbuf_offset;
@@ -1056,9 +1058,21 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
 	 * array, to looks like that guest actually send such packet.
 	 *
 	 * Check user_send_rarp() for more information.
+	 *
+	 * broadcast_rarp shares a cacheline in the virtio_net structure
+	 * with some fields that are accessed during enqueue and
+	 * rte_atomic16_cmpset() causes a write if using cmpxchg. This could
+	 * result in false sharing between enqueue and dequeue.
+	 *
+	 * Prevent unnecessary false sharing by reading broadcast_rarp first
+	 * and only performing cmpset if the read indicates it is likely to
+	 * be set.
 	 */
-	if (unlikely(rte_atomic16_cmpset((volatile uint16_t *)
-					 &dev->broadcast_rarp.cnt, 1, 0))) {
+
+	if (unlikely(rte_atomic16_read(&dev->broadcast_rarp) &&
+			rte_atomic16_cmpset((volatile uint16_t *)
+				&dev->broadcast_rarp.cnt, 1, 0))) {
+
 		rarp_mbuf = rte_pktmbuf_alloc(mbuf_pool);
 		if (rarp_mbuf == NULL) {
 			RTE_LOG(ERR, VHOST_DATA,