libvirt users - Jan 2011 - Getting CPU and memory usage statistics for the host

Hi,

I have noticed that virt-manager has the ability to show me the current cpu- and
memory-usage of both the host and running guest machines.

How does it do that?

I could make good use of that information myself in the client applications
I'm
writing, however, from what I can see on 
http://libvirt.org/html/libvirt-libvirt.html, I have no idea how to go about 
getting it from libvirt. In fact, before I've seen virt-manager, I just
assumed
libvirt cannot do that at all, and was planning to manually ssh to the host and 
read statistics from /proc when I'd need them.

I've tried looking at the virt-manager source code to find out how to do
this,
but it appears I would have to learn Python first in order to understand it.

Could someone please give me some pointers?

Regards,

	Guido

If your client application is being written in C, you might want to
take a look at the Host sFlow source code:

http://host-sflow.sourceforge.net/

The Host sFlow agent locally polls counters using libvirt and then
exports them using the sFlow protocol.

You might want to think about adding sFlow support to your
application. Passively receiving the counters over UDP is simpler and
more scalable than counter polling. You can also use sFlow to monitor
the physical server statistics and traffic through the virtual switch
to get a complete picture of performance.

http://blog.sflow.com/2010/10/sflowtrend-adds-server-performance.html



On Wed, Jan 19, 2011 at 8:18 AM, Guido Winkelmann
<guido-libvi at unknownsite.de> wrote:
> Hi,
>
> I have noticed that virt-manager has the ability to show me the current
cpu- and
> memory-usage of both the host and running guest machines.
>
> How does it do that?
>
> I could make good use of that information myself in the client applications
I'm
> writing, however, from what I can see on
> http://libvirt.org/html/libvirt-libvirt.html, I have no idea how to go
about
> getting it from libvirt. In fact, before I've seen virt-manager, I just
assumed
> libvirt cannot do that at all, and was planning to manually ssh to the host
and
> read statistics from /proc when I'd need them.
>
> I've tried looking at the virt-manager source code to find out how to
do this,
> but it appears I would have to learn Python first in order to understand
it.
>
> Could someone please give me some pointers?
>
> Regards,
>
> ? ? ? ?Guido
>
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>