On Wed, Jan 18, 2017 at 03:02:02PM +0800, Jason Wang wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> drivers/vhost/net.c | 23 ++++++++++++++++++++---
> 1 file changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 5dc3465..c42e9c3 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -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);
> --
> 2.7.4
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