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Commit 0ed005ce authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

vhost_net: tx batching 



This patch tries to utilize tuntap rx batching by peeking the tx
virtqueue during transmission, if there's more available buffers in
the virtqueue, set MSG_MORE flag for a hint for backend (e.g tuntap)
to batch the packets.

Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 275bf960

drivers/vhost/net.c

+20 −3
Original line number Diff line number Diff line
@@ -351,6 +351,15 @@ static int vhost_net_tx_get_vq_desc(struct vhost_net *net, 
	return r;

}



static bool vhost_exceeds_maxpend(struct vhost_net *net)

{

	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];

	struct vhost_virtqueue *vq = &nvq->vq;



	return (nvq->upend_idx + vq->num - VHOST_MAX_PEND) % UIO_MAXIOV

		== nvq->done_idx;

}



/* Expects to be always run from workqueue - which acts as

 * read-size critical section for our kind of RCU. */

static void handle_tx(struct vhost_net *net)
@@ -394,8 +403,7 @@ static void handle_tx(struct vhost_net *net) 
		/* If more outstanding DMAs, queue the work.

		 * Handle upend_idx wrap around

		 */

		if (unlikely((nvq->upend_idx + vq->num - VHOST_MAX_PEND)

			      % UIO_MAXIOV == nvq->done_idx))

		if (unlikely(vhost_exceeds_maxpend(net)))

			break;



		head = vhost_net_tx_get_vq_desc(net, vq, vq->iov,
@@ -454,6 +462,16 @@ static void handle_tx(struct vhost_net *net) 
			msg.msg_control = NULL;

			ubufs = NULL;

		}



		total_len += len;

		if (total_len < VHOST_NET_WEIGHT &&

		    !vhost_vq_avail_empty(&net->dev, vq) &&

		    likely(!vhost_exceeds_maxpend(net))) {

			msg.msg_flags |= MSG_MORE;

		} else {

			msg.msg_flags &= ~MSG_MORE;

		}



		/* TODO: Check specific error and bomb out unless ENOBUFS? */

		err = sock->ops->sendmsg(sock, &msg, len);

		if (unlikely(err < 0)) {
@@ -472,7 +490,6 @@ static void handle_tx(struct vhost_net *net) 
			vhost_add_used_and_signal(&net->dev, vq, head, 0);

		else

			vhost_zerocopy_signal_used(net, vq);

		total_len += len;

		vhost_net_tx_packet(net);

		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {

			vhost_poll_queue(&vq->poll);