[Qemu-devel] [Bug 654913] Re: Windows XP uses 200% CPU when given 2 VCPUs

[Michael Tokarev]

I see no problems in my tests wrt SMP performance (tried two cores only
so far).  MPS variant in winXP works noticeable slower in my case,
apparently due to CPU wastage.  ACPI variant runs almost at native speed
(when run in winXP booted on bare metal) - I tried some simple multi-
treaded java benchmarks.  So I'm not quite sure what are you asking.

Yet again, on _slightly_ loaded guest, MPS variant works a bit better,
but I just confirmed by previous guess - switching to performance
cpufreq governor restores that, but without CPU wastage.

-- 
Windows XP uses 200% CPU when given 2 VCPUs
https://bugs.launchpad.net/bugs/654913
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Status in QEMU: Invalid

Bug description:
When using libvirt to give a domain 2 CPUs (<domain 
type='kvm'><vcpu>2</vcpu></domain>), the Windows XP kvm process will use 200% 
CPU when Windows is idle. Switching the number of CPUs back to 1, the kvm 
process gives normal idle percentages.

Using libvirt 0.8.3-1ubuntu9, tried with the following qemu-kvm packages:

qemu-kvm_0.12.4+noroms-0ubuntu7_amd64.deb
qemu-kvm_0.12.5+noroms-0ubuntu4_amd64.deb

The smp flag being set by libvirt is:

-smp 2,sockets=2,cores=1,threads=1