| Message ID | 1490069087-4783-9-git-send-email-jasowang@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@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); > I don't see which patch adds __skb_array_empty. > @@ -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
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@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); >> > 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 > >> @@ -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
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@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); > > 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
On 2017年03月30日 10:33, Michael S. Tsirkin wrote: > 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@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); >>> 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. Ok, rethink about this, since skb_array could be resized, using lockless version seems wrong. For the comment of using compiler barrier, caller (vhost_net_rx_peek_head_len) uses cpu_relax(). But I haven't figured out why a compiler barrier is needed here. Could you please explain? Thanks > >>>> @@ -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
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();
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@redhat.com> --- drivers/vhost/net.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)