On Thu, Mar 30, 2017 at 10:16:15AM +0800, Jason Wang wrote:
>
>
> On 2017年03月29日 20:07, Michael S. Tsirkin wrote:
> > On Tue, Mar 21, 2017 at 12:04:47PM +0800, Jason Wang wrote:
> > > 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@xxxxxxxxxx>
> > > ---
> > > 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);
> > I don't see which patch adds __skb_array_empty.
>
> This is not something new, it was introduced by ad69f35d1dc0a ("skb_array:
> array based FIFO for skbs").
>
> Thanks
Same comment about a compiler barrier applies then.
> >
> > > @@ -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
