Hi everyone,
using libvirt I'm trying to calculate cpu utilization of a node in
percent. But sometimes values beyond 100.0% are being calculated.
This is because a domain spend more time on a cpu than time is
elapsed in the meantime.
A short explanation of the way how cpu utilization is computed in my
case:
1. - open two connections with
conn_cur/conn_old = virConnectOpenReadOnly(NULL);
2. - get current time
gettimeofday(&time_old, NULL);
- get domain by id with
dom_old = virDomainLookupByID(conn_old, id)
- get domain information
virDomainGetInfo(dom_old, &info_old);
3. - sleep a second
4. - doing same stuff like in 2. but with _cur
5. - compute cpu utilization by dividing used cputime by elapsed time
and multiply with 100
Am I right if I suppose that cpuTime for _virDomainInfo structure
will be directly acquired from the hypervisor in virDomainGetInfo
(dom_old, &info_old) or is it already present with getting the domain
itself? Is there any better solution of doing this, which is more
precise?
And another general question:
The monitoring utility of xen, called xentop, provides also
statistics about networking and vbds. Are there any plans to provide
this values by libvirt in the future?
Cheers,
Jan
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