Merge tag 'sound-fix-4.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai...

[linux-2.6-microblaze.git] / drivers / net / virtio_net.c

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 59b0e97..63c7810 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -749,9 +749,9 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
 {
        struct receive_queue *rq =
                container_of(napi, struct receive_queue, napi);
-       unsigned int r, received = 0;
+       unsigned int r, received;
 
-       received += virtnet_receive(rq, budget - received);
+       received = virtnet_receive(rq, budget);
 
        /* Out of packets? */
        if (received < budget) {
@@ -939,8 +939,16 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
        skb_orphan(skb);
        nf_reset(skb);
 
-       /* Apparently nice girls don't return TX_BUSY; stop the queue
-        * before it gets out of hand.  Naturally, this wastes entries. */
+       /* If running out of space, stop queue to avoid getting packets that we
+        * are then unable to transmit.
+        * An alternative would be to force queuing layer to requeue the skb by
+        * returning NETDEV_TX_BUSY. However, NETDEV_TX_BUSY should not be
+        * returned in a normal path of operation: it means that driver is not
+        * maintaining the TX queue stop/start state properly, and causes
+        * the stack to do a non-trivial amount of useless work.
+        * Since most packets only take 1 or 2 ring slots, stopping the queue
+        * early means 16 slots are typically wasted.
+        */
        if (sq->vq->num_free < 2+MAX_SKB_FRAGS) {
                netif_stop_subqueue(dev, qnum);
                if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {