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vhost_net: remove tx polling state

Browse source 
After commit 2b8b328b61 (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: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2013-04-10 20:50:48 +00:00 committed by David S. Miller
parent 16e3d9648a
commit 70181d5120
2 changed files with 9 additions and 68 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

74
drivers/vhost/net.c
View file

@ -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,

3
drivers/vhost/vhost.c
View file

@ -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);