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Re: [virt-tools-list] [PATCH] manager: show guest machine stats under Details -> Performance.



On Mon, 2013-04-29 at 17:30 +0100, Daniel P. Berrange wrote: 
> On Mon, Apr 29, 2013 at 12:23:27PM -0400, Cole Robinson wrote:
> > 
> > Thanks, pushed now.

Cole, thanks for accepting the patch.

> > This screen needs some work though. The memory stats are basically useless,
> > since it's a very rare operation that VM memory allocation is changed, so the
> > graph will always appear to be a straight line.

Yes, I completely agree. When I was preparing this patch, I also wanted
to plot the actual memory usage inside the guest. However, since I
didn't know how to obtain this info, I left it as is.

> There is an API for fetching
> > actual memory usage from inside the guest, however I think it's fairly
> > heavyweight so we couldn't just plug it in to the existing graph.
> 
> There is the virDomainGetMemoryStats API which on QEMU is wired through
> to the 'query-balloon' monitor command. This doesn't do calls into the
> guest OS at all - the guest pushes stats down the host asynchronously
> from this. So performance / scalability is on a par with the existing
> APIs for querying disk stats.

I've searched for 'virDomainGetMemoryStats' in the libvirt's API
(http://libvirt.org/html/libvirt-libvirt.html), but I couldn't find
anything. Though, there is a function with a similar name:
'virNodeGetMemoryStats'.
Could it be used to obtain guest memory usage stats?

Tadej


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