[PATCH V2 1/2] vhost_net: stop polling socket during rx processing

[Jason Wang]

We don't stop rx polling socket during rx processing, this will lead
unnecessary wakeups from under layer net devices (E.g
sock_def_readable() form tun). Rx will be slowed down in this
way. This patch avoids this by stop polling socket during rx
processing. A small drawback is that this introduces some overheads in
light load case because of the extra start/stop polling, but single
netperf TCP_RR does not notice any change. In a super heavy load case,
e.g using pktgen to inject packet to guest, we get about ~8.8%
improvement on pps:

before: ~1240000 pkt/s
after:  ~1350000 pkt/s

Signed-off-by: Jason Wang <jasow...@redhat.com>
---
 drivers/vhost/net.c | 56 +++++++++++++++++++++++++++--------------------------
 1 file changed, 29 insertions(+), 27 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 10ff494..e91603b 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -301,6 +301,32 @@ static bool vhost_can_busy_poll(struct vhost_dev *dev,
               !vhost_has_work(dev);
 }
 
+static void vhost_net_disable_vq(struct vhost_net *n,
+                                struct vhost_virtqueue *vq)
+{
+       struct vhost_net_virtqueue *nvq =
+               container_of(vq, struct vhost_net_virtqueue, vq);
+       struct vhost_poll *poll = n->poll + (nvq - n->vqs);
+       if (!vq->private_data)
+               return;
+       vhost_poll_stop(poll);
+}
+
+static int vhost_net_enable_vq(struct vhost_net *n,
+                               struct vhost_virtqueue *vq)
+{
+       struct vhost_net_virtqueue *nvq =
+               container_of(vq, struct vhost_net_virtqueue, vq);
+       struct vhost_poll *poll = n->poll + (nvq - n->vqs);
+       struct socket *sock;
+
+       sock = vq->private_data;
+       if (!sock)
+               return 0;
+
+       return vhost_poll_start(poll, sock->file);
+}
+
 static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
                                    struct vhost_virtqueue *vq,
                                    struct iovec iov[], unsigned int iov_size,
@@ -627,6 +653,7 @@ static void handle_rx(struct vhost_net *net)
        if (!sock)
                goto out;
        vhost_disable_notify(&net->dev, vq);
+       vhost_net_disable_vq(net, vq);
 
        vhost_hlen = nvq->vhost_hlen;
        sock_hlen = nvq->sock_hlen;
@@ -715,9 +742,10 @@ static void handle_rx(struct vhost_net *net)
                total_len += vhost_len;
                if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
                        vhost_poll_queue(&vq->poll);
-                       break;
+                       goto out;
                }
        }
+       vhost_net_enable_vq(net, vq);
 out:
        mutex_unlock(&vq->mutex);
 }
@@ -796,32 +824,6 @@ static int vhost_net_open(struct inode *inode, struct file 
*f)
        return 0;
 }
 
-static void vhost_net_disable_vq(struct vhost_net *n,
-                                struct vhost_virtqueue *vq)
-{
-       struct vhost_net_virtqueue *nvq =
-               container_of(vq, struct vhost_net_virtqueue, vq);
-       struct vhost_poll *poll = n->poll + (nvq - n->vqs);
-       if (!vq->private_data)
-               return;
-       vhost_poll_stop(poll);
-}
-
-static int vhost_net_enable_vq(struct vhost_net *n,
-                               struct vhost_virtqueue *vq)
-{
-       struct vhost_net_virtqueue *nvq =
-               container_of(vq, struct vhost_net_virtqueue, vq);
-       struct vhost_poll *poll = n->poll + (nvq - n->vqs);
-       struct socket *sock;
-
-       sock = vq->private_data;
-       if (!sock)
-               return 0;
-
-       return vhost_poll_start(poll, sock->file);
-}
-
 static struct socket *vhost_net_stop_vq(struct vhost_net *n,
                                        struct vhost_virtqueue *vq)
 {
-- 
1.8.3.1