[PATCH net-next V2 2/3] vhost_net: tx batching
From: Jason Wang <jasowang@redhat.com>
Date: 2016-12-28 08:10:23
Also in:
kvm, lkml, netdev
Subsystem:
the rest, virtio host (vhost) · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", Jason Wang
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. Signed-off-by: Jason Wang <jasowang@redhat.com> --- 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