Imported Upstream version 16.11.2

[deb_dpdk.git] / lib / librte_vhost / virtio_net.c

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 337470d..ea027f1 100644 (file)
--- 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,