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vhost_net: tx batching

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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: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2017-01-18 15:02:02 +08:00 committed by David S. Miller
parent 275bf960ac
commit 0ed005ce02
1 changed files with 20 additions and 3 deletions
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23
drivers/vhost/net.c
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@ -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);