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

[su disheng]

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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