[PATCH net-next 3/3] virtio-net: clean tx descriptors from rx napi

[Willem de Bruijn]

From: Willem de Bruijn <will...@google.com>

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 <will...@google.com>
---
 drivers/net/virtio_net.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 95d938e82080..af830eb212bf 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1030,12 +1030,34 @@ static int virtnet_receive(struct receive_queue *rq, 
int budget)
        return received;
 }
 
+static void free_old_xmit_skbs(struct send_queue *sq);
+
+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;
+
+       __netif_tx_lock(txq, smp_processor_id());
+       free_old_xmit_skbs(sq);
+       __netif_tx_unlock(txq);
+
+       if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
+               netif_wake_subqueue(vi->dev, vq2txq(sq->vq));
+}
+
 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? */
-- 
2.12.2.564.g063fe858b8-goog