[PATCH net-next 8/8] vhost_net: use lockless peeking for skb array during busy polling

Jason Wang
Tue, 21 Mar 2017 04:04:47 -0000

For the socket that exports its skb array, we can use lockless polling
to avoid touching spinlock during busy polling.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/net.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 53f09f2..41153a3 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -551,10 +551,13 @@ static int peek_head_len(struct vhost_net_virtqueue *rvq,
struct sock *sk)
 	return len;
 }

-static int sk_has_rx_data(struct sock *sk)
+static int sk_has_rx_data(struct vhost_net_virtqueue *rvq, struct sock *sk)
 {
 	struct socket *sock = sk->sk_socket;

+	if (rvq->rx_array)
+		return !__skb_array_empty(rvq->rx_array);
+
 	if (sock->ops->peek_len)
 		return sock->ops->peek_len(sock);

@@ -579,7 +582,7 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net,
 		endtime = busy_clock() + vq->busyloop_timeout;

 		while (vhost_can_busy_poll(&net->dev, endtime) &&
-		       !sk_has_rx_data(sk) &&
+		       !sk_has_rx_data(rvq, sk) &&
 		       vhost_vq_avail_empty(&net->dev, vq))
 			cpu_relax();

--
2.7.4