[libvirt-users] Monitoring KVM Machine Uptimes

Hey folks. Currently, I am working on an accounting-solution for Private Cloud with Eucalyptus as my bachelor-thesis. Eucalyptus bases on libvirt providing the KVM machines. Part of the thesis is kind of measurement for the uptimes of each instance in the cloud. As Eucalyptus is based on libvirt, i want to know if there is kind of tool already setup for monitoring a vm in terms of uptimes, cputimes and disk i/o. If not, can anyone give me a hint, how i could grep these facts? I found a tool called "virt-top" which monitors the vm, but for me there is to much overhead. Thanks for you support. cheers, Karsten