[Qemu-devel] qemu-kvm idle guest using 10% cpu and causes significant increase of read_hpet calls on host

[Qemu-devel] qemu-kvm idle guest using 10% cpu and causes significant increase of read_hpet calls on host

[Dennis Jacobfeuerborn]

Hi,
I've started running a Centos6 minimal install virtual machine on a 
Centost6 host and noticed that even when the guest is completely idle the 
qemu-kvm process on the host shows up with 10% cpu usage on in "top".

Using perf and oprofile I noticed that once the guest is running the amount 
of read_hpet calls increases by a factor of 10. So I went and booted the 
host with "hpet=disable" which resulted in the qemu-kvm process now showing 
up with 15% cpu usage instead of 10%. So this seems to have an impact but 
certainly not the intended one.

I'm not well versed in these matters so I'm looking for any pointers in 
terms of for example kernel options I could test on the guest/host to find 
out what the cause of this is.

I opened a bug here:
http://bugs.centos.org/view.php?id=5028

According to one developer this is also seen by users on RHEL6 and SL6 
which is why I decided to ask for help here since it doesn't seem to be a 
distribution specific problem.

Regards,
   Dennis