| Message ID | 1464760594-30326-3-git-send-email-jasowang@redhat.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On Wed, Jun 01, 2016 at 01:56:34AM -0400, Jason Wang wrote: > We always poll tx for socket, this is sub optimal since: > > - it will be only used when we exceed the sndbuf of the socket. > - since we use two independent polls for tx and vq, this will slightly > increase the waitqueue traversing time and more important, vhost > could not benefit from commit > 9e641bdcfa4ef4d6e2fbaa59c1be0ad5d1551fd5 ("net-tun: restructure > tun_do_read for better sleep/wakeup efficiency") even if we've > stopped rx polling during handle_rx since tx poll were still left in > the waitqueue. > > Fix this by conditionally enable tx polling only when -EAGAIN were > met. > > Test shows about 8% improvement on guest rx pps. > > Before: ~1350000 > After: ~1460000 > > Signed-off-by: Jason Wang <jasowang@redhat.com> > --- > drivers/vhost/net.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index 1d3e45f..e75ffcc 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -378,6 +378,7 @@ static void handle_tx(struct vhost_net *net) > goto out; > > vhost_disable_notify(&net->dev, vq); > + vhost_net_disable_vq(net, vq); > > hdr_size = nvq->vhost_hlen; > zcopy = nvq->ubufs; > @@ -459,6 +460,8 @@ static void handle_tx(struct vhost_net *net) > % UIO_MAXIOV; > } > vhost_discard_vq_desc(vq, 1); > + if (err == -EAGAIN) > + vhost_net_enable_vq(net, vq); > break; > } > if (err != len) This seems rather risky. What if TX failed for some other reason? Polling won't ever be re-enabled ... > -- > 1.8.3.1
On 2016年06月07日 20:26, Michael S. Tsirkin wrote: > On Wed, Jun 01, 2016 at 01:56:34AM -0400, Jason Wang wrote: >> We always poll tx for socket, this is sub optimal since: >> >> - it will be only used when we exceed the sndbuf of the socket. >> - since we use two independent polls for tx and vq, this will slightly >> increase the waitqueue traversing time and more important, vhost >> could not benefit from commit >> 9e641bdcfa4ef4d6e2fbaa59c1be0ad5d1551fd5 ("net-tun: restructure >> tun_do_read for better sleep/wakeup efficiency") even if we've >> stopped rx polling during handle_rx since tx poll were still left in >> the waitqueue. >> >> Fix this by conditionally enable tx polling only when -EAGAIN were >> met. >> >> Test shows about 8% improvement on guest rx pps. >> >> Before: ~1350000 >> After: ~1460000 >> >> Signed-off-by: Jason Wang <jasowang@redhat.com> >> --- >> drivers/vhost/net.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c >> index 1d3e45f..e75ffcc 100644 >> --- a/drivers/vhost/net.c >> +++ b/drivers/vhost/net.c >> @@ -378,6 +378,7 @@ static void handle_tx(struct vhost_net *net) >> goto out; >> >> vhost_disable_notify(&net->dev, vq); >> + vhost_net_disable_vq(net, vq); >> >> hdr_size = nvq->vhost_hlen; >> zcopy = nvq->ubufs; >> @@ -459,6 +460,8 @@ static void handle_tx(struct vhost_net *net) >> % UIO_MAXIOV; >> } >> vhost_discard_vq_desc(vq, 1); >> + if (err == -EAGAIN) >> + vhost_net_enable_vq(net, vq); >> break; >> } >> if (err != len) > This seems rather risky. What if TX failed for some other reason? > Polling won't ever be re-enabled ... > But why we need to enable tx poll in this case? Even if we enable it, we wont' get any wakeup. >> -- >> 1.8.3.1
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 1d3e45f..e75ffcc 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -378,6 +378,7 @@ static void handle_tx(struct vhost_net *net) goto out; vhost_disable_notify(&net->dev, vq); + vhost_net_disable_vq(net, vq); hdr_size = nvq->vhost_hlen; zcopy = nvq->ubufs; @@ -459,6 +460,8 @@ static void handle_tx(struct vhost_net *net) % UIO_MAXIOV; } vhost_discard_vq_desc(vq, 1); + if (err == -EAGAIN) + vhost_net_enable_vq(net, vq); break; } if (err != len)
We always poll tx for socket, this is sub optimal since: - it will be only used when we exceed the sndbuf of the socket. - since we use two independent polls for tx and vq, this will slightly increase the waitqueue traversing time and more important, vhost could not benefit from commit 9e641bdcfa4ef4d6e2fbaa59c1be0ad5d1551fd5 ("net-tun: restructure tun_do_read for better sleep/wakeup efficiency") even if we've stopped rx polling during handle_rx since tx poll were still left in the waitqueue. Fix this by conditionally enable tx polling only when -EAGAIN were met. Test shows about 8% improvement on guest rx pps. Before: ~1350000 After: ~1460000 Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/vhost/net.c | 3 +++ 1 file changed, 3 insertions(+)