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vhost_net: Avoid rx queue wake-ups during busypoll

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We may run handle_rx() while rx work is queued. For example a packet can
push the rx work during the window before handle_rx calls
vhost_net_disable_vq().
In that case busypoll immediately exits due to vhost_has_work()
condition and enables vq again. This can lead to another unnecessary rx
wake-ups, so poll rx work instead of enabling the vq.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Toshiaki Makita 2018-07-03 16:31:33 +09:00 committed by David S. Miller
parent 027b17603b
commit be294a51ad
1 changed files with 19 additions and 7 deletions
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26
drivers/vhost/net.c
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@ -653,7 +653,8 @@ static void vhost_rx_signal_used(struct vhost_net_virtqueue *nvq)
nvq->done_idx = 0;
}
static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
bool *busyloop_intr)
{
struct vhost_net_virtqueue *rnvq = &net->vqs[VHOST_NET_VQ_RX];
struct vhost_net_virtqueue *tnvq = &net->vqs[VHOST_NET_VQ_TX];
@ -671,11 +672,16 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
preempt_disable();
endtime = busy_clock() + tvq->busyloop_timeout;
while (vhost_can_busy_poll(endtime) &&
!vhost_has_work(&net->dev) &&
!sk_has_rx_data(sk) &&
vhost_vq_avail_empty(&net->dev, tvq))
while (vhost_can_busy_poll(endtime)) {
if (vhost_has_work(&net->dev)) {
*busyloop_intr = true;
break;
}
if (sk_has_rx_data(sk) ||
!vhost_vq_avail_empty(&net->dev, tvq))
break;
cpu_relax();
}
preempt_enable();
@ -795,6 +801,7 @@ static void handle_rx(struct vhost_net *net)
s16 headcount;
size_t vhost_hlen, sock_hlen;
size_t vhost_len, sock_len;
bool busyloop_intr = false;
struct socket *sock;
struct iov_iter fixup;
__virtio16 num_buffers;
@ -818,7 +825,9 @@ static void handle_rx(struct vhost_net *net)
vq->log : NULL;
mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk))) {
while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk,
&busyloop_intr))) {
busyloop_intr = false;
sock_len += sock_hlen;
vhost_len = sock_len + vhost_hlen;
headcount = get_rx_bufs(vq, vq->heads + nvq->done_idx,
@ -905,7 +914,10 @@ static void handle_rx(struct vhost_net *net)
goto out;
}
}
vhost_net_enable_vq(net, vq);
if (unlikely(busyloop_intr))
vhost_poll_queue(&vq->poll);
else
vhost_net_enable_vq(net, vq);
out:
vhost_rx_signal_used(nvq);
mutex_unlock(&vq->mutex);