[libvirt] Re: [Libvir] How to get the memory used by a guest domin

On Wed, Apr 30, 2008 at 01:57:21PM +0100, Daniel P. Berrange wrote: Dan means collectd, from http://collectd.org/ I'll emphasize what Dan said: The only way to reliably get things like real memory usage, process lists and so on from the guest is to run some agent/program inside the guest. This is how VMWare does it. I've been chipping away at these restrictions, because I think it'd be useful for sysadmins to be able to see guest status from the dom0 without needing to install software in the guests. For disk usage, we now have virt-df (http://et.redhat.com/~rjones/virt-df/) which runs entirely in the dom0. Virt-df works by parsing the guest's disk image -- a hard but tractable problem that turns out to give pretty reliable results in most scenarios. However for getting guest memory / process lists the situation is much more complicated. You'd need to peek into the guest's memory and read kernel structures, a very complex problem indeed (and not even tractable on a certain popular closed-source operating system). A more tractable alternative is to run an agent in the guest which is common and widely available, such as a simple kernel module that shares data over a common host <-> guest bus. It would be kind of like virtio [http://lwn.net/Articles/239238/] for monitoring. Rich. -- Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into Xen guests. http://et.redhat.com/~rjones/virt-p2v