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Message-Id: <1482912571-3157-3-git-send-email-jasowang@redhat.com> Date: Wed, 28 Dec 2016 16:09:30 +0800 From: Jason Wang <jasowang@...hat.com> To: mst@...hat.com, kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Cc: Jason Wang <jasowang@...hat.com> Subject: [PATCH net-next V2 2/3] 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. Signed-off-by: Jason Wang <jasowang@...hat.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
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