Commit be294a51 authored by Toshiaki Makita's avatar Toshiaki Makita Committed by David S. Miller
Browse files

vhost_net: Avoid rx queue wake-ups during busypoll 



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: default avatarToshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 027b1760

drivers/vhost/net.c

+19 −7
Original line number Diff line number Diff line
@@ -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,
@@ -905,6 +914,9 @@ static void handle_rx(struct vhost_net *net) 
			goto out;

		}

	}

	if (unlikely(busyloop_intr))

		vhost_poll_queue(&vq->poll);

	else

		vhost_net_enable_vq(net, vq);

out:

	vhost_rx_signal_used(nvq);

CRA Git | Maintained and supported by SUSTech CRA and CCSE