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Re: [libvirt] Is it possible to use more then 2 CPUs in the guest?

Tom Hughes schrieb:
On 06/08/09 12:36, Daniel P. Berrange wrote:
On Wed, Aug 05, 2009 at 10:11:07AM +0200, Mirko Raasch wrote:

in my server i use an Intel Quad Core CPU and i want to use in one
WindowsXP guest all 4 cores.
The device manager shows four CPU (Qemu Virtual CPU version 0.10.5).
When i start prime95 or superpi, only 2 of them are in use. CPU-Z shows
also 2 Cores, instead of 4 like the device manager.

I don't know what those apps are, but they sound broken to me. If the
guest has been launched with 4 virtual CPus, the guest OS should be
able to use them, regardless of what your host core/socket/thread cpu
topology is. KVM/QEMU allow upto 16  virtual CPUs IIRC, and this is
totally independant of how many physical CPUs you have.

As other people have already said, it's a Windows licensing thing where some versions of Windows are designed to only work on a limited number of physical CPU packages. So they will run 4-way on a quad core but not on four single core CPUs.

So it is seeing all the cores and reporting them in task manager but only allowing two to be used by programs.


I tried Windows 7 Ultimate and its the same like in WinXP, only two Cores are in use. The other two cores are bored. It does not matter whether I emulate four, six or eight cpu in the guest, in the host only two of four cores are in use.

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