Slow TCP performance from Win2k8R2 guests under Linux KVM

Slow TCP performance from Win2k8R2 guests under Linux KVM

[Gordon Messmer]

Would anyone be so kind as to test the performance of TCP streams on 
Windows 2k8R2 guests of KVM virt servers?

Red Hat's virtio-win-1.6.3 package was published to address a problem 
described as "low performance" on Win2k8 guests.  Actual performance was 
not recorded in the bug report.

On my KVM servers, Windows 2k8R2 guests are able to send data at less 
than 4Mbps.  I test this by using netcat on Windows and piping a file to 
its input.  The receiving end of the transfer is an un-virtualized 
CentOS system.  Transfer rate is measured by selecting the stream in 
iptraf while it is active.

UDP transfers, such as by CIFS, will send data at around 400Mbps.

TCP transfers from Windows 2012 or Windows 8 are not similarly affected.

The same driver for Win2k8 was published by Red Hat in virtio-win 1.6.3, 
1.6.4, and 1.6.5.

Does anyone see TCP transfer rates from Win2k8R2 that don't look 
ridiculously slow?

https://bugzilla.redhat.com/show_bug.cgi?id=859882
http://rhn.redhat.com/errata/RHBA-2013-0441.html
http://joncraton.org/blog/46/netcat-for-windows

Re: Slow TCP performance from Win2k8R2 guests under Linux KVM

[Yan Vugenfirer]

On Jul 16, 2013, at 1:10 AM, Gordon Messmer wrote:

> Would anyone be so kind as to test the performance of TCP streams on Windows 2k8R2 guests of KVM virt servers?
> 
> Red Hat's virtio-win-1.6.3 package was published to address a problem described as "low performance" on Win2k8 guests.  Actual performance was not recorded in the bug report.
> 
> On my KVM servers, Windows 2k8R2 guests are able to send data at less than 4Mbps.  I test this by using netcat on Windows and piping a file to its input.  The receiving end of the transfer is an un-virtualized CentOS system.  Transfer rate is measured by selecting the stream in iptraf while it is active.
> 

Can you provide results with iperf or netperf?


Thanks,
Yan.


> UDP transfers, such as by CIFS, will send data at around 400Mbps.
> 
> TCP transfers from Windows 2012 or Windows 8 are not similarly affected.
> 
> The same driver for Win2k8 was published by Red Hat in virtio-win 1.6.3, 1.6.4, and 1.6.5.
> 
> Does anyone see TCP transfer rates from Win2k8R2 that don't look ridiculously slow?
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=859882
> http://rhn.redhat.com/errata/RHBA-2013-0441.html
> http://joncraton.org/blog/46/netcat-for-windows
> 
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Re: Slow TCP performance from Win2k8R2 guests under Linux KVM

[Gordon Messmer]

On 07/21/2013 03:32 AM, Yan Vugenfirer wrote:
> Can you provide results with iperf or netperf?

Actually, iperf seems to operate at expected speeds, while some other 
applications don't.  I'm working on getting a list of some of the 
affected programs.  I believe my users first reported the problem with 
ftp.  I'll follow up as soon as possible.

Thanks for the suggestion.

Re: Slow TCP performance from Win2k8R2 guests under Linux KVM

[Yan Vugenfirer]

Can you try the latest drivers: http://alt.fedoraproject.org/pub/alt/virtio-win/latest/images/

Best regards,
Yan.


On Jul 23, 2013, at 8:24 AM, Gordon Messmer wrote:

> On 07/21/2013 03:32 AM, Yan Vugenfirer wrote:
>> Can you provide results with iperf or netperf?
> 
> Actually, iperf seems to operate at expected speeds, while some other applications don't.  I'm working on getting a list of some of the affected programs.  I believe my users first reported the problem with ftp.  I'll follow up as soon as possible.
> 
> Thanks for the suggestion.
> 
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