Patchwork [5/5] virtio-net: Switch default to new bottom half TX handler for iothread

login
register
mail settings
Submitter Alex Williamson
Date Aug. 27, 2010, 10:37 p.m.
Message ID <20100827223745.2696.18845.stgit@s20.home>
Download mbox | patch
Permalink /patch/62881/
State New
Headers show

Comments

Alex Williamson - Aug. 27, 2010, 10:37 p.m.
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.williamson@redhat.com>
---

 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(-)
Michael S. Tsirkin - Aug. 31, 2010, 8:25 p.m.
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.williamson@redhat.com>

parameter having different settings based on config
options might surprise some users. I don't think
we really need a parameter here ...

> ---
> 
>  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 majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
Alex Williamson - Aug. 31, 2010, 10:32 p.m.
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.williamson@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.  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?
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 majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
Anthony Liguori - Aug. 31, 2010, 10:46 p.m.
On 08/31/2010 05:32 PM, 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.williamson@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.  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?
>    

No, at this stage, we should ignore no --enable-io-thread with -enable-kvm.

Regards,

Anthony Liguori

> 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 majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>        
>
>
>
Stefan Hajnoczi - Sept. 1, 2010, 6:21 a.m.
On Tue, Aug 31, 2010 at 11:32 PM, Alex Williamson
<alex.williamson@redhat.com> 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.williamson@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.  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?
> Thanks,
>
> Alex

qemu-kvm uses its own iothread implementation by default.  It doesn't
need --enable-io-thread because it already uses a similar model.

Stefan

>
>> > ---
>> >
>> >  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 majordomo@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 majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
Michael S. Tsirkin - Sept. 1, 2010, 8:47 a.m.
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.williamson@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 majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
>

Patch

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
+
 /* Base devices.  */
 VirtIODevice *virtio_blk_init(DeviceState *dev, BlockConf *conf);
 VirtIODevice *virtio_net_init(DeviceState *dev, NICConf *conf,