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Commit 70181d51 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

vhost_net: remove tx polling state 



After commit 2b8b328b (vhost_net: handle polling
errors when setting backend), we in fact track the polling state through
poll->wqh, so there's no need to duplicate the work with an extra
vhost_net_polling_state. So this patch removes this and make the code simpler.

This patch also removes the all tx starting/stopping code in tx path according
to Michael's suggestion.

Netperf test shows almost the same result in stream test, but gets improvements
on TCP_RR tests (both zerocopy or copy) especially on low load cases.

Tested between multiqueue kvm guest and external host with two direct
connected 82599s.

zerocopy disabled:

sessions|transaction rates|normalize|
before/after/+improvements
1 | 9510.24/11727.29/+23.3%    | 693.54/887.68/+28.0%   |
25| 192931.50/241729.87/+25.3% | 2376.80/2771.70/+16.6% |
50| 277634.64/291905.76/+5%    | 3118.36/3230.11/+3.6%  |

zerocopy enabled:

sessions|transaction rates|normalize|
before/after/+improvements
1 | 7318.33/11929.76/+63.0%    | 521.86/843.30/+61.6%   |
25| 167264.88/242422.15/+44.9% | 2181.60/2788.16/+27.8% |
50| 272181.02/294347.04/+8.1%  | 3071.56/3257.85/+6.1%  |

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 16e3d964

drivers/vhost/net.c

+6 −68
Original line number Diff line number Diff line
@@ -64,20 +64,10 @@ enum { 
	VHOST_NET_VQ_MAX = 2,

};



enum vhost_net_poll_state {

	VHOST_NET_POLL_DISABLED = 0,

	VHOST_NET_POLL_STARTED = 1,

	VHOST_NET_POLL_STOPPED = 2,

};



struct vhost_net {

	struct vhost_dev dev;

	struct vhost_virtqueue vqs[VHOST_NET_VQ_MAX];

	struct vhost_poll poll[VHOST_NET_VQ_MAX];

	/* Tells us whether we are polling a socket for TX.

	 * We only do this when socket buffer fills up.

	 * Protected by tx vq lock. */

	enum vhost_net_poll_state tx_poll_state;

	/* Number of TX recently submitted.

	 * Protected by tx vq lock. */

	unsigned tx_packets;
@@ -155,28 +145,6 @@ static void copy_iovec_hdr(const struct iovec *from, struct iovec *to, 
	}

}



/* Caller must have TX VQ lock */

static void tx_poll_stop(struct vhost_net *net)

{

	if (likely(net->tx_poll_state != VHOST_NET_POLL_STARTED))

		return;

	vhost_poll_stop(net->poll + VHOST_NET_VQ_TX);

	net->tx_poll_state = VHOST_NET_POLL_STOPPED;

}



/* Caller must have TX VQ lock */

static int tx_poll_start(struct vhost_net *net, struct socket *sock)

{

	int ret;



	if (unlikely(net->tx_poll_state != VHOST_NET_POLL_STOPPED))

		return 0;

	ret = vhost_poll_start(net->poll + VHOST_NET_VQ_TX, sock->file);

	if (!ret)

		net->tx_poll_state = VHOST_NET_POLL_STARTED;

	return ret;

}



/* In case of DMA done not in order in lower device driver for some reason.

 * upend_idx is used to track end of used idx, done_idx is used to track head

 * of used idx. Once lower device DMA done contiguously, we will signal KVM
@@ -242,7 +210,7 @@ static void handle_tx(struct vhost_net *net) 
		.msg_flags = MSG_DONTWAIT,

	};

	size_t len, total_len = 0;

	int err, wmem;

	int err;

	size_t hdr_size;

	struct socket *sock;

	struct vhost_ubuf_ref *uninitialized_var(ubufs);
@@ -253,19 +221,9 @@ static void handle_tx(struct vhost_net *net) 
	if (!sock)

		return;



	wmem = atomic_read(&sock->sk->sk_wmem_alloc);

	if (wmem >= sock->sk->sk_sndbuf) {

		mutex_lock(&vq->mutex);

		tx_poll_start(net, sock);

		mutex_unlock(&vq->mutex);

		return;

	}



	mutex_lock(&vq->mutex);

	vhost_disable_notify(&net->dev, vq);



	if (wmem < sock->sk->sk_sndbuf / 2)

		tx_poll_stop(net);

	hdr_size = vq->vhost_hlen;

	zcopy = vq->ubufs;
@@ -285,23 +243,14 @@ static void handle_tx(struct vhost_net *net) 
		if (head == vq->num) {

			int num_pends;



			wmem = atomic_read(&sock->sk->sk_wmem_alloc);

			if (wmem >= sock->sk->sk_sndbuf * 3 / 4) {

				tx_poll_start(net, sock);

				set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);

				break;

			}

			/* If more outstanding DMAs, queue the work.

			 * Handle upend_idx wrap around

			 */

			num_pends = likely(vq->upend_idx >= vq->done_idx) ?

				    (vq->upend_idx - vq->done_idx) :

				    (vq->upend_idx + UIO_MAXIOV - vq->done_idx);

			if (unlikely(num_pends > VHOST_MAX_PEND)) {

				tx_poll_start(net, sock);

				set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);

			if (unlikely(num_pends > VHOST_MAX_PEND))

				break;

			}

			if (unlikely(vhost_enable_notify(&net->dev, vq))) {

				vhost_disable_notify(&net->dev, vq);

				continue;
@@ -364,8 +313,6 @@ static void handle_tx(struct vhost_net *net) 
					UIO_MAXIOV;

			}

			vhost_discard_vq_desc(vq, 1);

			if (err == -EAGAIN || err == -ENOBUFS)

				tx_poll_start(net, sock);

			break;

		}

		if (err != len)
@@ -628,7 +575,6 @@ static int vhost_net_open(struct inode *inode, struct file *f) 


	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev);

	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);

	n->tx_poll_state = VHOST_NET_POLL_DISABLED;



	f->private_data = n;
@@ -638,32 +584,24 @@ static int vhost_net_open(struct inode *inode, struct file *f) 
static void vhost_net_disable_vq(struct vhost_net *n,

				 struct vhost_virtqueue *vq)

{

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

	if (!vq->private_data)

		return;

	if (vq == n->vqs + VHOST_NET_VQ_TX) {

		tx_poll_stop(n);

		n->tx_poll_state = VHOST_NET_POLL_DISABLED;

	} else

		vhost_poll_stop(n->poll + VHOST_NET_VQ_RX);

	vhost_poll_stop(poll);

}



static int vhost_net_enable_vq(struct vhost_net *n,

				struct vhost_virtqueue *vq)

{

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

	struct socket *sock;

	int ret;



	sock = rcu_dereference_protected(vq->private_data,

					 lockdep_is_held(&vq->mutex));

	if (!sock)

		return 0;

	if (vq == n->vqs + VHOST_NET_VQ_TX) {

		n->tx_poll_state = VHOST_NET_POLL_STOPPED;

		ret = tx_poll_start(n, sock);

	} else

		ret = vhost_poll_start(n->poll + VHOST_NET_VQ_RX, sock->file);



	return ret;

	return vhost_poll_start(poll, sock->file);

}



static struct socket *vhost_net_stop_vq(struct vhost_net *n,

drivers/vhost/vhost.c

+3 −0
Original line number Diff line number Diff line
@@ -89,6 +89,9 @@ int vhost_poll_start(struct vhost_poll *poll, struct file *file) 
	unsigned long mask;

	int ret = 0;



	if (poll->wqh)

		return 0;



	mask = file->f_op->poll(file, &poll->table);

	if (mask)

		vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);