[Libvir] Add a timestamp to virDomainInfo ?

The primary use of the virDomainInfo data is in calculating resource utilization over time. The CPU runtime data, however, is represented as a counter, so to calulate utilization requires some transformations. Basically subtract the CPU runtime value for time X, from the value at time Y, and divide the result by Y-X. Obviously this requires us to know the times X & Y. Currently the virDomainInfo structure does not contain this information though, so apps have to call something like gettimeofday() before virDomainGetInfo(), to record the timestamp of each virDomainInfo record. The problem is that this is a pretty poor approximation - particularly if libvirt is talking via XenD, a non-trivial period of time can pass between the call to gettimeofday() and the values for virDomainInfo actually sampled. Thus I would like to suggest that the virtDomainInfo structure be expanded to add an extra data field of type 'struct timeval' to record a high resolution timestamp. Now currently this wouldn't help accuracy all that much, since libvirt would still be filling this in much the same way as the app did. It does however, open the door to having Xen itself provide an accurate timestamp back to libvirt, which would in turn benefit apps without requiring further code change. Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|