Re: [Libvir] libvirt and accessing remote systems

On Wed, Jan 24, 2007 at 11:48:47PM +0000, Daniel P. Berrange wrote: > On Wed, Jan 24, 2007 at 02:17:31PM +0000, Richard W.M. Jones wrote: > > * Another proposal was to make all libvirt calls remote > > (http://people.redhat.com/berrange/libvirt/libvirt-arch-remote-3.png) > > but I don't think this is a going concern because (1) it requires > > a daemon always be run, which is another installation problem and > > another chance for sysadmins to give up, and (2) the perception will > > be that this is slow, whether or not that is actually true. > > I'd never compared performance of direct hypercalls vs libvirt_proxy > before, so I did a little test. The most commonly called method is > virt-manager is virDomainGetInfo for fetching current status of a > running domain - we call that once a second per guest. > > So I wrote a simple program in C which calls virDomainGetInfo 100,000 > times for 3 active guest VMs. I ran the test under a couple of different > libvirt backends. The results were: > > 1. As root, direct hypercalls -> 1.4 seconds > 2. As non-root, hypercalls via libvirt_proxy -> 9 seconds > 3. As non-root, via XenD -> 45 minutes [1] > > So although it is x10 slower than hypercalls, the libvirt_proxy is > actaully pretty damn fast - 9 seconds for 300,000 calls. Interesting figures, I has expected the proxy inter-process communication to slow things down more, I guess it works well because scheduling follows exactly the message passing so there is little latency in the RPC, was that on a uniprocessor machine ?

> [1] It didn't actually finish after 45 seconds. I just got bored of waiting. s/seconds/minutes/ I guess, and you checked CPU was at 100% not a bad deadlock somewhere, right ;-) ?