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Commit 8241a1e4 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

vhost_net: stop polling socket during rx processing 



We don't stop rx polling socket during rx processing, this will lead
unnecessary wakeups from under layer net devices (E.g
sock_def_readable() form tun). Rx will be slowed down in this
way. This patch avoids this by stop polling socket during rx
processing. A small drawback is that this introduces some overheads in
light load case because of the extra start/stop polling, but single
netperf TCP_RR does not notice any change. In a super heavy load case,
e.g using pktgen to inject packet to guest, we get about ~8.8%
improvement on pps:

before: ~1240000 pkt/s
after:  ~1350000 pkt/s

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 aaa76724

drivers/vhost/net.c

+33 −31
Original line number Diff line number Diff line
@@ -301,6 +301,32 @@ static bool vhost_can_busy_poll(struct vhost_dev *dev, 
	       !vhost_has_work(dev);

}



static void vhost_net_disable_vq(struct vhost_net *n,

				 struct vhost_virtqueue *vq)

{

	struct vhost_net_virtqueue *nvq =

		container_of(vq, struct vhost_net_virtqueue, vq);

	struct vhost_poll *poll = n->poll + (nvq - n->vqs);

	if (!vq->private_data)

		return;

	vhost_poll_stop(poll);

}



static int vhost_net_enable_vq(struct vhost_net *n,

				struct vhost_virtqueue *vq)

{

	struct vhost_net_virtqueue *nvq =

		container_of(vq, struct vhost_net_virtqueue, vq);

	struct vhost_poll *poll = n->poll + (nvq - n->vqs);

	struct socket *sock;



	sock = vq->private_data;

	if (!sock)

		return 0;



	return vhost_poll_start(poll, sock->file);

}



static int vhost_net_tx_get_vq_desc(struct vhost_net *net,

				    struct vhost_virtqueue *vq,

				    struct iovec iov[], unsigned int iov_size,
@@ -613,6 +639,7 @@ static void handle_rx(struct vhost_net *net) 
	if (!sock)

		goto out;

	vhost_disable_notify(&net->dev, vq);

	vhost_net_disable_vq(net, vq);



	vhost_hlen = nvq->vhost_hlen;

	sock_hlen = nvq->sock_hlen;
@@ -629,7 +656,7 @@ static void handle_rx(struct vhost_net *net) 
					likely(mergeable) ? UIO_MAXIOV : 1);

		/* On error, stop handling until the next kick. */

		if (unlikely(headcount < 0))

			break;

			goto out;

		/* On overrun, truncate and discard */

		if (unlikely(headcount > UIO_MAXIOV)) {

			iov_iter_init(&msg.msg_iter, READ, vq->iov, 1, 1);
@@ -648,7 +675,7 @@ static void handle_rx(struct vhost_net *net) 
			}

			/* Nothing new?  Wait for eventfd to tell us

			 * they refilled. */

			break;

			goto out;

		}

		/* We don't need to be notified again. */

		iov_iter_init(&msg.msg_iter, READ, vq->iov, in, vhost_len);
@@ -676,7 +703,7 @@ static void handle_rx(struct vhost_net *net) 
					 &fixup) != sizeof(hdr)) {

				vq_err(vq, "Unable to write vnet_hdr "

				       "at addr %p\n", vq->iov->iov_base);

				break;

				goto out;

			}

		} else {

			/* Header came from socket; we'll need to patch
@@ -692,7 +719,7 @@ static void handle_rx(struct vhost_net *net) 
				 &fixup) != sizeof num_buffers) {

			vq_err(vq, "Failed num_buffers write");

			vhost_discard_vq_desc(vq, headcount);

			break;

			goto out;

		}

		vhost_add_used_and_signal_n(&net->dev, vq, vq->heads,

					    headcount);
@@ -701,9 +728,10 @@ static void handle_rx(struct vhost_net *net) 
		total_len += vhost_len;

		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {

			vhost_poll_queue(&vq->poll);

			break;

			goto out;

		}

	}

	vhost_net_enable_vq(net, vq);

out:

	mutex_unlock(&vq->mutex);

}
@@ -782,32 +810,6 @@ static int vhost_net_open(struct inode *inode, struct file *f) 
	return 0;

}



static void vhost_net_disable_vq(struct vhost_net *n,

				 struct vhost_virtqueue *vq)

{

	struct vhost_net_virtqueue *nvq =

		container_of(vq, struct vhost_net_virtqueue, vq);

	struct vhost_poll *poll = n->poll + (nvq - n->vqs);

	if (!vq->private_data)

		return;

	vhost_poll_stop(poll);

}



static int vhost_net_enable_vq(struct vhost_net *n,

				struct vhost_virtqueue *vq)

{

	struct vhost_net_virtqueue *nvq =

		container_of(vq, struct vhost_net_virtqueue, vq);

	struct vhost_poll *poll = n->poll + (nvq - n->vqs);

	struct socket *sock;



	sock = vq->private_data;

	if (!sock)

		return 0;



	return vhost_poll_start(poll, sock->file);

}



static struct socket *vhost_net_stop_vq(struct vhost_net *n,

					struct vhost_virtqueue *vq)

{