Commit 03088137 authored by Jason Wang's avatar Jason Wang Committed by Michael S. Tsirkin

vhost_net: basic polling support

This patch tries to poll for new added tx buffer or socket receive
queue for a while at the end of tx/rx processing. The maximum time
spent on polling were specified through a new kind of vring ioctl.
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent d4a60603
......@@ -287,6 +287,43 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
rcu_read_unlock_bh();
}
static inline unsigned long busy_clock(void)
{
return local_clock() >> 10;
}
static bool vhost_can_busy_poll(struct vhost_dev *dev,
unsigned long endtime)
{
return likely(!need_resched()) &&
likely(!time_after(busy_clock(), endtime)) &&
likely(!signal_pending(current)) &&
!vhost_has_work(dev);
}
static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
struct vhost_virtqueue *vq,
struct iovec iov[], unsigned int iov_size,
unsigned int *out_num, unsigned int *in_num)
{
unsigned long uninitialized_var(endtime);
int r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
out_num, in_num, NULL, NULL);
if (r == vq->num && vq->busyloop_timeout) {
preempt_disable();
endtime = busy_clock() + vq->busyloop_timeout;
while (vhost_can_busy_poll(vq->dev, endtime) &&
vhost_vq_avail_empty(vq->dev, vq))
cpu_relax_lowlatency();
preempt_enable();
r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
out_num, in_num, NULL, NULL);
}
return r;
}
/* 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)
......@@ -331,10 +368,9 @@ static void handle_tx(struct vhost_net *net)
% UIO_MAXIOV == nvq->done_idx))
break;
head = vhost_get_vq_desc(vq, vq->iov,
ARRAY_SIZE(vq->iov),
&out, &in,
NULL, NULL);
head = vhost_net_tx_get_vq_desc(net, vq, vq->iov,
ARRAY_SIZE(vq->iov),
&out, &in);
/* On error, stop handling until the next kick. */
if (unlikely(head < 0))
break;
......@@ -435,6 +471,38 @@ static int peek_head_len(struct sock *sk)
return len;
}
static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
{
struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
struct vhost_virtqueue *vq = &nvq->vq;
unsigned long uninitialized_var(endtime);
int len = peek_head_len(sk);
if (!len && vq->busyloop_timeout) {
/* Both tx vq and rx socket were polled here */
mutex_lock(&vq->mutex);
vhost_disable_notify(&net->dev, vq);
preempt_disable();
endtime = busy_clock() + vq->busyloop_timeout;
while (vhost_can_busy_poll(&net->dev, endtime) &&
skb_queue_empty(&sk->sk_receive_queue) &&
vhost_vq_avail_empty(&net->dev, vq))
cpu_relax_lowlatency();
preempt_enable();
if (vhost_enable_notify(&net->dev, vq))
vhost_poll_queue(&vq->poll);
mutex_unlock(&vq->mutex);
len = peek_head_len(sk);
}
return len;
}
/* This is a multi-buffer version of vhost_get_desc, that works if
* vq has read descriptors only.
* @vq - the relevant virtqueue
......@@ -553,7 +621,7 @@ static void handle_rx(struct vhost_net *net)
vq->log : NULL;
mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
while ((sock_len = peek_head_len(sock->sk))) {
while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk))) {
sock_len += sock_hlen;
vhost_len = sock_len + vhost_hlen;
headcount = get_rx_bufs(vq, vq->heads, vhost_len,
......
......@@ -303,6 +303,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq->memory = NULL;
vhost_reset_is_le(vq);
vhost_disable_cross_endian(vq);
vq->busyloop_timeout = 0;
}
static int vhost_worker(void *data)
......@@ -937,6 +938,19 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
case VHOST_GET_VRING_ENDIAN:
r = vhost_get_vring_endian(vq, idx, argp);
break;
case VHOST_SET_VRING_BUSYLOOP_TIMEOUT:
if (copy_from_user(&s, argp, sizeof(s))) {
r = -EFAULT;
break;
}
vq->busyloop_timeout = s.num;
break;
case VHOST_GET_VRING_BUSYLOOP_TIMEOUT:
s.index = idx;
s.num = vq->busyloop_timeout;
if (copy_to_user(argp, &s, sizeof(s)))
r = -EFAULT;
break;
default:
r = -ENOIOCTLCMD;
}
......
......@@ -115,6 +115,7 @@ struct vhost_virtqueue {
/* Ring endianness requested by userspace for cross-endian support. */
bool user_be;
#endif
u32 busyloop_timeout;
};
struct vhost_dev {
......
......@@ -126,6 +126,12 @@ struct vhost_memory {
#define VHOST_SET_VRING_CALL _IOW(VHOST_VIRTIO, 0x21, struct vhost_vring_file)
/* Set eventfd to signal an error */
#define VHOST_SET_VRING_ERR _IOW(VHOST_VIRTIO, 0x22, struct vhost_vring_file)
/* Set busy loop timeout (in us) */
#define VHOST_SET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x23, \
struct vhost_vring_state)
/* Get busy loop timeout (in us) */
#define VHOST_GET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x24, \
struct vhost_vring_state)
/* VHOST_NET specific defines */
......
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