Linux Virtualization - Sep 2018 - [PATCH net-next v8 3/7] net: vhost: factor out busy polling logic to vhost_net_busy_poll()

On Tue, Aug 21, 2018 at 11:15 AM Jason Wang <jasowang at redhat.com>
wrote:
>
>
>
> On 2018?08?19? 20:11, xiangxia.m.yue at gmail.com wrote:
> > From: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> >
> > Factor out generic busy polling logic and will be
> > used for in tx path in the next patch. And with the patch,
> > qemu can set differently the busyloop_timeout for rx queue.
> >
> > To avoid duplicate codes, introduce the helper functions:
> > * sock_has_rx_data(changed from sk_has_rx_data)
> > * vhost_net_busy_poll_try_queue
> >
> > Signed-off-by: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> > ---
> >   drivers/vhost/net.c | 111
+++++++++++++++++++++++++++++++++-------------------
> >   1 file changed, 71 insertions(+), 40 deletions(-)
> >
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > index 32c1b52..453c061 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -440,6 +440,75 @@ static void vhost_net_signal_used(struct
vhost_net_virtqueue *nvq)
> >       nvq->done_idx = 0;
> >   }
> >
> > +static int sock_has_rx_data(struct socket *sock)
> > +{
> > +     if (unlikely(!sock))
> > +             return 0;
> > +
> > +     if (sock->ops->peek_len)
> > +             return sock->ops->peek_len(sock);
> > +
> > +     return skb_queue_empty(&sock->sk->sk_receive_queue);
> > +}
> > +
> > +static void vhost_net_busy_poll_try_queue(struct vhost_net *net,
> > +                                       struct vhost_virtqueue *vq)
> > +{
> > +     if (!vhost_vq_avail_empty(&net->dev, vq)) {
> > +             vhost_poll_queue(&vq->poll);
> > +     } else if (unlikely(vhost_enable_notify(&net->dev, vq)))
{
> > +             vhost_disable_notify(&net->dev, vq);
> > +             vhost_poll_queue(&vq->poll);
> > +     }
> > +}
> > +
> > +static void vhost_net_busy_poll(struct vhost_net *net,
> > +                             struct vhost_virtqueue *rvq,
> > +                             struct vhost_virtqueue *tvq,
> > +                             bool *busyloop_intr,
> > +                             bool poll_rx)
> > +{
> > +     unsigned long busyloop_timeout;
> > +     unsigned long endtime;
> > +     struct socket *sock;
> > +     struct vhost_virtqueue *vq = poll_rx ? tvq : rvq;
> > +
> > +     mutex_lock_nested(&vq->mutex, poll_rx ? VHOST_NET_VQ_TX:
VHOST_NET_VQ_RX);
> > +     vhost_disable_notify(&net->dev, vq);
> > +     sock = rvq->private_data;
> > +
> > +     busyloop_timeout = poll_rx ? rvq->busyloop_timeout:
> > +                                  tvq->busyloop_timeout;
> > +
> > +     preempt_disable();
> > +     endtime = busy_clock() + busyloop_timeout;
> > +
> > +     while (vhost_can_busy_poll(endtime)) {
> > +             if (vhost_has_work(&net->dev)) {
> > +                     *busyloop_intr = true;
> > +                     break;
> > +             }
> > +
> > +             if ((sock_has_rx_data(sock) &&
> > +                  !vhost_vq_avail_empty(&net->dev, rvq)) ||
> > +                 !vhost_vq_avail_empty(&net->dev, tvq))
> > +                     break;
> > +
> > +             cpu_relax();
> > +     }
> > +
> > +     preempt_enable();
> > +
> > +     if (poll_rx)
> > +             vhost_net_busy_poll_try_queue(net, tvq);
> > +     else if (sock_has_rx_data(sock))
> > +             vhost_net_busy_poll_try_queue(net, rvq);
>
> This could be simplified like:
>
> if (poll_rx || sock_has_rx_data(sock))
>      vhost_net_busy_poll_try_queue(net, vq);
done, thanks
> Thanks
>
> > +     else /* On tx here, sock has no rx data. */
> > +             vhost_enable_notify(&net->dev, rvq);
> > +
> > +     mutex_unlock(&vq->mutex);
> > +}
> > +
> >   static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
> >                                   struct vhost_net_virtqueue *nvq,
> >                                   unsigned int *out_num, unsigned int
*in_num,
> > @@ -753,16 +822,6 @@ static int peek_head_len(struct
vhost_net_virtqueue *rvq, struct sock *sk)
> >       return len;
> >   }
> >
> > -static int sk_has_rx_data(struct sock *sk)
> > -{
> > -     struct socket *sock = sk->sk_socket;
> > -
> > -     if (sock->ops->peek_len)
> > -             return sock->ops->peek_len(sock);
> > -
> > -     return skb_queue_empty(&sk->sk_receive_queue);
> > -}
> > -
> >   static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct
sock *sk,
> >                                     bool *busyloop_intr)
> >   {
> > @@ -770,41 +829,13 @@ static int vhost_net_rx_peek_head_len(struct
vhost_net *net, struct sock *sk,
> >       struct vhost_net_virtqueue *tnvq =
&net->vqs[VHOST_NET_VQ_TX];
> >       struct vhost_virtqueue *rvq = &rnvq->vq;
> >       struct vhost_virtqueue *tvq = &tnvq->vq;
> > -     unsigned long uninitialized_var(endtime);
> >       int len = peek_head_len(rnvq, sk);
> >
> > -     if (!len && tvq->busyloop_timeout) {
> > +     if (!len && rvq->busyloop_timeout) {
> >               /* Flush batched heads first */
> >               vhost_net_signal_used(rnvq);
> >               /* Both tx vq and rx socket were polled here */
> > -             mutex_lock_nested(&tvq->mutex, VHOST_NET_VQ_TX);
> > -             vhost_disable_notify(&net->dev, tvq);
> > -
> > -             preempt_disable();
> > -             endtime = busy_clock() + tvq->busyloop_timeout;
> > -
> > -             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,
rvq)) ||
> > -                         !vhost_vq_avail_empty(&net->dev,
tvq))
> > -                             break;
> > -                     cpu_relax();
> > -             }
> > -
> > -             preempt_enable();
> > -
> > -             if (!vhost_vq_avail_empty(&net->dev, tvq)) {
> > -                     vhost_poll_queue(&tvq->poll);
> > -             } else if
(unlikely(vhost_enable_notify(&net->dev, tvq))) {
> > -                     vhost_disable_notify(&net->dev, tvq);
> > -                     vhost_poll_queue(&tvq->poll);
> > -             }
> > -
> > -             mutex_unlock(&tvq->mutex);
> > +             vhost_net_busy_poll(net, rvq, tvq, busyloop_intr, true);
> >
> >               len = peek_head_len(rnvq, sk);
> >       }
>