[libvirt-users] cpu time totals

Igor Serebryany igor47 at moomers.org
Tue Sep 13 21:46:24 UTC 2011


	I'm comparing the cpu usage of a VM from virDomainGetInfo and the
	usages returned per-vcpu from virDomainGetVcpus and the totals do
	not match up. 

	I expect that the cpu usages reported per-vcpu, when summed, should
	equal the total cpu usage of the domain, but there is quite a large
	gap between them. Is there something I'm missing?

	See this example code using the python bindings:

>>> import libvirt
>>> c = libvirt.open('qemu:///system')
>>> d = c.lookupByID(51)
>>> d.info()[4]
>>> d.vcpus()[0]
[(0, 1, 12720000000L, 1), (1, 1, 2980000000L, 0), (2, 1, 3150000000L, 1), (3, 1, 2600000000L, 0)]
>>> sum([vcpu[2] for vcpu in d.vcpus()[0]])
>>> d.info()[4] - sum([vcpu[2] for vcpu in d.vcpus()[0]])

	Why is this additional 91 seconds not reflected in time spent by the
	vcpus? What exactly is the meaning of the cpuTime parameter of the
	virVcpuInfo struct?

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