Re: [PATCH net-next RFC 4/4] virtio-net: clean tx descriptors from rx napi

quoted

+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);
+
+       __netif_tx_lock(txq, smp_processor_id());
+       free_old_xmit_skbs(sq, sq->napi.weight);
+       __netif_tx_unlock(txq);

Should we check tx napi weight here? Or this was treated as an independent
optimization?

Good point. This was not intended to run in no-napi mode as is.
With interrupts disabled most of the time in that mode, I don't
expect it to be worthwhile using in that case. I'll add the check
for sq->napi.weight != 0.

quoted

+
+       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 =

@@ -1039,6 +1056,8 @@ static int virtnet_poll(struct napi_struct *napi,

int budget)
        received = virtnet_receive(rq, budget);
  +     virtnet_poll_cleantx(rq);
+

Better to do the before virtnet_receive() consider refill may allocate
memory for rx buffers.

Will do.

Btw, if this is proved to be more efficient. In the future we may consider
to:

1) use a single interrupt for both rx and tx
2) use a single napi to handle both rx and tx

Agreed, I think that's sensible.