On Thu, Jan 25, 2007 at 04:56:23AM -0500, Daniel Veillard wrote:
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 ?
It was a dual core machine, so there wasn't so much process-contention as you'd get on UP.
[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 ;-) ?
Of course I meant minutes here :-) At least 60% of the CPU time was the usual XenStoreD doing stupid amounts of I/O problem. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|