[libvirt] Current cpu and memory usage for Host and Domains

su disheng disheng.su at gmail.com
Mon Jan 18 20:10:46 UTC 2010

On Sun, Jan 17, 2010 at 5:02 AM, Daniel P. Berrange <berrange at redhat.com>wrote:

> On Fri, Jan 15, 2010 at 11:52:09AM -0800, su disheng wrote:
> > Seem there is no way to get host CPU usage in libvirt API? I can get
> > freeMemory by  virNodeGetFreeMemory, but no cpu usage API.
> > How about add a new api for it? The host CPU usage is also important for
> VM
> > creation and migration decision, like the free memory.
> > Yes, I know, I can got it from "top"...:)
> We've historically thought that monitoring of the host OS is out of
> scope of the libvirt API, since there are already a huge variety of
> monitoring services / APIs available for people.  I wonder if we need
> to reconsider that now we have the VMWare drivers though - apps using
> libvirt don't get to installl stuff in VMWare host OS, so the only
> access to some of this host CPU data is probably via the VMWare APIs.
> Which in turn suggests we'd need to expose some minimal hosting API
> for this in libvirt
Like this happened in the future, one APIs for both host and guest.
Especially, for KVM,
there is no much difference to get the both host and guest, cpu/disk/nic
statistic data.

> FWIW, virt-top/virt-manager calculates host CPU usage by summing the usage
> of all guests over a fixed time slice. This will be an underestimate of
> true host utilization though, since it can't see CPU usage for non-guest
> related processes

For Xen like hypervisors, by summing the usage of all guests is OK, but for
KVM, it's
better to include other non-guest related processes.

> Daniel
> --
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