[fedora-virt] Idle VM is hogging host cpu

[Daniel P. Berrange]

On Mon, Nov 08, 2010 at 04:00:09AM +0100, Dennis Jacobfeuerborn wrote:
> Hi,
> I just migrated from Fedora 11 to Fedora 14 (via a fresh install) and so 
> far everything seems fine kvm seems to have major issues.
> After starting one Centos 5 VM qemu-kvm keeps using 20% of the cpu 
> according to top even though the VM is completely idle. Does anyone have a 
> clue what might cause this because I wasn't seeing this behavior under 
> Fedora 11.

Try adding   divider=10  to the kernel boot command line for the guest.
This will make it use a 100HZ tick rate, instead of 1000HZ, lowering the
background idle load on the host. I doubt it accounts for 20%, but it is
always worth doing for RHEL5 kernels since they don't have tickless mode.

Regards,
Daniel
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