On Mon, May 30, 2016 at 02:47:53AM -0400, Jason Wang wrote:
> 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,
BTW we might want to rename these functions, name no longer
reflects function ...
> @@ -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);
OK so if sock is readable but RX VQ is empty, this will
immediately schedule another round of handle_rx and so ad
infinitum,
Looks like a bug.
> 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
