[Xen-users] Re: XEN ans Windows SMP

["Oliver Wilcock" <oliver@xxxxxxx>]

> Date: Mon, 24 Nov 2008 08:01:35 -0500
> From: "Venefax" <venefax@xxxxxxxxx>
>
> There is an amazing problem between XEN and Windows 2003 SMP. For
> instance, a 1 CPU Windows VM takes 0.7 percent while running idle, but if
> you add a second CPU, still idle, the percentage shoots up to 3.6%. As a
> result, you can only have a few Windows SMP machines. Is there a solution
> to make the SMP simulation more efficient in XEN?
> Federico

By SMP so you mean you are using a non-ACPI HAL?  (perhaps acpi=0 in your
config?)  Or do you mean you played with the vcpus=2 setting?

CPU AMD 64?
64 bit hypervisor?
32 bit Windows?
Linux distribution and Xen version?

I'm trying to find out why my experience with a 64 bit hypervisor and 32
bit Windows gives such lousy performance (I've seen a few other people
mention it, but I believe most don't have the problem).

When using an ACPI Multiprocessor HAL I see idle CPU usage (xm top) closer
to 112% when vcpus=2 and the DomU guest VM is sluggish.  I'm using SLES 10
SP2 on AMD X2 with ASUS M2N-LR.  I plan to experiment with other CPUs and
kernels when I have a chance.



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