[Xen-users] Xen 3.0.3 Multiple VCPU performance issue

["Jeroen Torrekens" <jeroen.torrekens@xxxxxxxxxxx>]

Dear List,

 

We are running Xen 3.0.3 with a ubuntu dom0 (2.6.16 linux kernel). We have done some tests with a tool that calculate prime numbers. On a VM with one core, it takes 2.5 seconds to calculate a series of prime numbers. If I create a VM with 2 VCPUs it takes 9 seconds. The domU is also an Ubuntu Dapper. The physical hardware consists of 2x Xeon 5160 inside an Intel barebone (SR2500ALLX) with an LSI raid controller and 16GB of memory. VT is enabled in the bios.

 

I know the tool only uses one thread, but it should take the same amount of time on both machines. The rest of the machine is identical (disk, memory, OS version, …). Someone has a hint on this where I can start my search on what is causing this behavior?

 

If you need more info, I’ll be happy to give it to you.

 

Thanks in advance!

 

Jeroen

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