Red Hat Bugzilla – Bug 277771
qemu-kvm utilizes large amounts of CPU on Windows XP
Last modified: 2008-08-02 19:40:36 EDT
Description of problem:
A Windows XP Virtual Machine (VM) uses 50% CPU according to Virtual Machine
Manager, even when Windows is idle (Core 2 Duo hardware).
Changing "/usr/bin/qemu-kvm" to "/usr/bin/qemu" creates a slower performing VM,
but with around 1-3% CPU utilization when Windows is idle.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Create a Windows XP virtual machine, with hardware acceleration enabled.
2. Install Windows XP and upgrade to Windows XP SP2 and install all latest
updates. You will see the high CPU utilization even when the install is waiting
for a prompt.
3. Within Windows, set Computer to "Standard PC", using Device Manager (or
during installation). Set graphics adapter hardware acceleration to None.
4. CPU utilization is still high.
CPU utilization is high when Windows XP is idle, using qemu-kvm, but low when
When Windows is idle, the CPU should have low utilization.
qemu-kvm is part of the kvm package, not of qemu, changing component and
Which kernel is this with? Does kvm-36 from -updates-testing help?
It's with 22.214.171.124-65.fc7 and 126.96.36.199-65.fc7PAE.
I haven't tried it on the older XEN kernel.
I'll try kvm-36 from updates testing and let you know.
updates-testing has this, according to yum:
kvm.i386 35-2.fc7 updates-testing
Do you want me to download the package from somewhere else?
BTW, I'm using Fedora 7.
I just tried kvm-35-2 and it doesn't boot my VMs.
No error message anywhere and silly libvirt doesn't let you look at the console
to see any messages (it flashes off very quickly).
Hope that helps, but doubt it does.
See #310591 for why -35 is not booting at all.
I do not see this problem with kvm-24. 2-4% CPU usage when the guest is idle.
Russell, you can boot the guest by hand outside virt-manager to see why it is
qemu-kvm -hda <path to disk image> -localtime -m 512
Grrr, bug #310591 ? HOw to get the auto bug link to work.
Sorry for the spam.
This link might be of use. ACPI virtualization is very slow in KVM. Disabling
ACPI in the guest makes it run with sane amounts of CPU.
kvm-36 is now in updates. If that does not work, I've just used kvm-60 from Rawhide on my F-8 machine
(Core 2 Duo, x86_64) with WinXP SP2 and it does not seem to be affected by the problem anymore.
The information we've requested above is required in order
to review this problem report further and diagnose/fix the
issue if it is still present. Since there have not been any
updates to the report since thirty (30) days or more since we
requested additional information, we're assuming the problem
is either no longer present in the current Fedora release, or
that there is no longer any interest in tracking the problem.
Setting status to "CLOSED INSUFFICIENT_DATA". If you still
experience this problem after updating to our latest Fedora
release and can provide the information previously requested,
please feel free to reopen the bug report.
Thank you in advance.
Note that maintenance for Fedora 7 will end 30 days after the GA of Fedora 9.