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

From: Michael Tokarev
Subject: [Qemu-devel] [Bug 654913] Re: Windows XP uses 200% CPU when given 2 VCPUs
Date: Wed, 20 Oct 2010 20:44:22 -0000

What I mean is that ACPI is required nowadays for any sane SMP.  Yes,
enabling ACPI.

Speaking of 200% CPU for "MPS" being faster than ACPI version - maybe
it's your cpufreq code, and switching from 'ondemand' to 'performance'
governer will make ACPI version faster?

I see no difference in speed between ACPI and non-ACPI version of a
_single_-CPU winXP, and my winXP does not boot at all (BSOD) with -smp 2
and -no-acpi.  I never tried to find out why, because felt it's not the
right way anyway (and it shows similar BSOD when wrongly switching
between ACPI and non-ACPI in winXP on many older (PIII etc) - again,
non-smp - boxes).


Windows XP uses 200% CPU when given 2 VCPUs
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Status in QEMU: New

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:


The smp flag being set by libvirt is:

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

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