virtio-net: clean tx descriptors from rx napi

Amortize the cost of virtual interrupts by doing both rx and tx work
on reception of a receive interrupt if tx napi is enabled. With
VIRTIO_F_EVENT_IDX, this suppresses most explicit tx completion
interrupts for bidirectional workloads.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4ec79e5d7a8643f0d5fe48645992b189a85d9a8c..9dd978f34c1fb00790faebbbae5b5b051dbf8a98 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1075,12 +1075,33 @@ static void free_old_xmit_skbs(struct send_queue *sq)
        u64_stats_update_end(&stats->tx_syncp);
 }
 
+static void virtnet_poll_cleantx(struct receive_queue *rq)
+{
+       struct virtnet_info *vi = rq->vq->vdev->priv;
+       unsigned int index = vq2rxq(rq->vq);
+       struct send_queue *sq = &vi->sq[index];
+       struct netdev_queue *txq = netdev_get_tx_queue(vi->dev, index);
+
+       if (!sq->napi.weight)
+               return;
+
+       if (__netif_tx_trylock(txq)) {
+               free_old_xmit_skbs(sq);
+               __netif_tx_unlock(txq);
+       }
+
+       if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
+               netif_tx_wake_queue(txq);
+}
+
 static int virtnet_poll(struct napi_struct *napi, int budget)
 {
        struct receive_queue *rq =
                container_of(napi, struct receive_queue, napi);
        unsigned int received;
 
+       virtnet_poll_cleantx(rq);
+
        received = virtnet_receive(rq, budget);
 
        /* Out of packets? */