[Xen-users] Windows DomU VT-d SMP Issues

[Darren Foo <darrenfoo@xxxxxxxxx>]

Hi,

I'm having some CPU usage issues with my Windows DomU (vcpu=1). Initially, 
CPU-Z, CPU Rightmark would show that the CPU multiplier on my Intel quad core 
Q6600 (2.4Ghz) was constantly flipping between x9 and x6. I ended up disabling 
Intel SpeedStep, C1E, and hardcoded the multiplier which seemed to stop the 
flipping. Now my problem is my TV streaming app will sometimes hit 100% CPU 
utilization and the streaming client stutters. When I try and set vcpu=2  it 
boots fine and all apps seem to work ok. But when I try to stream my TV, it 
fails. Application logs say that the client timed out. I ran a tcpdump to 
compare betwee vcpu=1 and 2 the only difference I can see is an RTSP ACK from 
the client with vcpu=2 which I don't see with vcpu=1. The TV streaming app uses 
my VT-d passed through DVB PCI card. I'm not running the GPLPV drivers since 
they currently disable my DVB card. I initially suspected UDP traffic might be 
affected in SMP Windows HVM, so I tried
 Iperf with UDP. When the Windows DomU has vcpu=2, remote IPerf UDP client to 
Windows DomU works, but Windows DomU to remote IPerf UDP server fails. However, 
I also tried a UDP connection using netcat which worked fine. Not sure what 
else to try. Any ideas? I have 4 cores, I'd like for my Windows DomU to use 2 
of them if possible.

Thanks

Darren


      

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