On Tue, Aug 31, 2010 at 04:32:54PM -0600, Alex Williamson wrote: > On Tue, 2010-08-31 at 23:25 +0300, Michael S. Tsirkin wrote: > > On Fri, Aug 27, 2010 at 04:37:45PM -0600, Alex Williamson wrote: > > > The bottom half handler shows big improvements over the timer > > > with few downsides, default to it when the iothread is enabled. > > > > > > Using the following tests, with the guest and host connected > > > via tap+bridge: > > > > > > guest> netperf -t TCP_STREAM -H $HOST > > > host> netperf -t TCP_STREAM -H $GUEST > > > guest> netperf -t UDP_STREAM -H $HOST > > > host> netperf -t UDP_STREAM -H $GUEST > > > guest> netperf -t TCP_RR -H $HOST > > > > > > Results: base throughput, exits/throughput -> > > > patched throughput, exits/throughput > > > > > > --enable-io-thread > > > TCP guest->host 2737.77, 47.82 -> 6767.09, 29.15 = 247%, 61% > > > TCP host->guest 2231.33, 74.00 -> 4125.80, 67.61 = 185%, 91% > > > UDP guest->host 6281.68, 14.66 -> 12569.27, 1.98 = 200%, 14% > > > UDP host->guest 275.91, 289.22 -> 264.80, 293.53 = 96%, 101% > > > interations/s 1949.65, 82.97 -> 7417.56, 84.31 = 380%, 102% > > > > > > No --enable-io-thread > > > TCP guest->host 3041.57, 55.11 -> 1038.93, 517.57 = 34%, 939% > > > TCP host->guest 2416.03, 76.67 -> 5655.92, 55.52 = 234%, 72% > > > UDP guest->host 12255.82, 6.11 -> 7775.87, 31.32 = 63%, 513% > > > UDP host->guest 587.92, 245.95 -> 611.88, 239.92 = 104%, 98% > > > interations/s 1975.59, 83.21 -> 8935.50, 88.18 = 452%, 106% > > > > > > Signed-off-by: Alex Williamson <alex.william...@redhat.com> > > > > parameter having different settings based on config > > options might surprise some users. I don't think > > we really need a parameter here ... > > I'm not a bit fan of this either, but I'd also prefer not to introduce a > regression for a performance difference we know about in advance.
I agree. The comment was mainly about a parameter. If we make it a hidden parameter (mainbe with x- prefix), this won't be an issue. > It gets even more complicated when we factor in qemu-kvm, as it doesn't > build with iothread enabled, but seems to get and even better boost in > performance across the board thanks largely to the kvm-irqchip. Should > we instead make this a configure option? --enable-virtio-net-txbh? That'll work too. > Thanks, > > Alex > > > > --- > > > > > > hw/s390-virtio-bus.c | 3 ++- > > > hw/syborg_virtio.c | 3 ++- > > > hw/virtio-pci.c | 3 ++- > > > hw/virtio.h | 6 ++++++ > > > 4 files changed, 12 insertions(+), 3 deletions(-) > > > > > > diff --git a/hw/s390-virtio-bus.c b/hw/s390-virtio-bus.c > > > index 1483362..985f99a 100644 > > > --- a/hw/s390-virtio-bus.c > > > +++ b/hw/s390-virtio-bus.c > > > @@ -328,7 +328,8 @@ static VirtIOS390DeviceInfo s390_virtio_net = { > > > .qdev.size = sizeof(VirtIOS390Device), > > > .qdev.props = (Property[]) { > > > DEFINE_NIC_PROPERTIES(VirtIOS390Device, nic), > > > - DEFINE_PROP_UINT32("txtimer", VirtIOS390Device, txtimer, 1), > > > + DEFINE_PROP_UINT32("txtimer", VirtIOS390Device, txtimer, > > > + TXTIMER_DEFAULT), > > > DEFINE_PROP_INT32("txburst", VirtIOS390Device, txburst, 256), > > > DEFINE_PROP_END_OF_LIST(), > > > }, > > > diff --git a/hw/syborg_virtio.c b/hw/syborg_virtio.c > > > index 7b76972..ee5746d 100644 > > > --- a/hw/syborg_virtio.c > > > +++ b/hw/syborg_virtio.c > > > @@ -300,7 +300,8 @@ static SysBusDeviceInfo syborg_virtio_net_info = { > > > .qdev.props = (Property[]) { > > > DEFINE_NIC_PROPERTIES(SyborgVirtIOProxy, nic), > > > DEFINE_VIRTIO_NET_FEATURES(SyborgVirtIOProxy, host_features), > > > - DEFINE_PROP_UINT32("txtimer", SyborgVirtIOProxy, txtimer, 1), > > > + DEFINE_PROP_UINT32("txtimer", SyborgVirtIOProxy, txtimer, > > > + TXTIMER_DEFAULT), > > > DEFINE_PROP_INT32("txburst", SyborgVirtIOProxy, txburst, 256), > > > DEFINE_PROP_END_OF_LIST(), > > > } > > > diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c > > > index e025c09..9740f57 100644 > > > --- a/hw/virtio-pci.c > > > +++ b/hw/virtio-pci.c > > > @@ -695,7 +695,8 @@ static PCIDeviceInfo virtio_info[] = { > > > DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 3), > > > DEFINE_VIRTIO_NET_FEATURES(VirtIOPCIProxy, host_features), > > > DEFINE_NIC_PROPERTIES(VirtIOPCIProxy, nic), > > > - DEFINE_PROP_UINT32("txtimer", VirtIOPCIProxy, txtimer, 1), > > > + DEFINE_PROP_UINT32("txtimer", VirtIOPCIProxy, txtimer, > > > + TXTIMER_DEFAULT), > > > DEFINE_PROP_INT32("txburst", VirtIOPCIProxy, txburst, 256), > > > DEFINE_PROP_END_OF_LIST(), > > > }, > > > diff --git a/hw/virtio.h b/hw/virtio.h > > > index 4051889..a1a17a2 100644 > > > --- a/hw/virtio.h > > > +++ b/hw/virtio.h > > > @@ -183,6 +183,12 @@ void virtio_update_irq(VirtIODevice *vdev); > > > void virtio_bind_device(VirtIODevice *vdev, const VirtIOBindings > > > *binding, > > > void *opaque); > > > > > > +#ifdef CONFIG_IOTHREAD > > > + #define TXTIMER_DEFAULT 0 > > > +#else > > > + #define TXTIMER_DEFAULT 1 > > > +#endif > > > + > > > > Add a comment explaning that this is just a performance optimization? > > > > > /* Base devices. */ > > > VirtIODevice *virtio_blk_init(DeviceState *dev, BlockConf *conf); > > > VirtIODevice *virtio_net_init(DeviceState *dev, NICConf *conf, > > > > > > -- > > > To unsubscribe from this list: send the line "unsubscribe kvm" in > > > the body of a message to majord...@vger.kernel.org > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html