[libvirt] Slow libvirtd startup

[Daniel P. Berrange]

On Wed, Jan 09, 2013 at 11:38:07PM +0200, Zeeshan Ali (Khattak) wrote:
> Hi,
>   Too lazy to explain again so I'll just c&p conversation I had about
> the issue with Eric on IRC:
> 
> <zeenix> is timeouts on session libvirt (or in general) something new?
> <zeenix> libvirtd startup seems to now take a few seconds so Boxes UI
> is all empty for that amount of time
> <eblake> it's been around for a while; qemu.conf has settings to
> control how long it should take
> <zeenix> unless Boxes is launched before libvirtd timesout
> <eblake> but there is a relatively new patch that makes the libvirtd
> -t actually be useful for qemu:///session
> <zeenix> don't think i ever changed that, at least not recently
> <zeenix> that could be it
> <zeenix> i only saw it happening after i update libvirtd (after a month)
> <eblake> if you're seeing some delays in starting libvirtd, those are
> probably worth fixing
> <zeenix> s/update/recently updated/
> <zeenix> yeah
> <zeenix> i'll try to write a test app
> <zeenix> no need, i can reproduce with virsh :)
> 
> [zeenix at z-laptop virt]$ time virsh list
>  Id    Name                           State
> ----------------------------------------------------
> 
> 
> real	0m6.349s
> user	0m0.016s
> sys	0m0.010s
> [zeenix at z-laptop virt]$ time virsh list
>  Id    Name                           State
> ----------------------------------------------------
> 
> 
> real	0m0.024s
> user	0m0.010s
> sys	0m0.011s

If I had to guess I'd blame the QEMU capabilities extraction.
I have a feeling probing via QMP is slower than just parsing
-help output. Though we cache the data, so in the future it
is much faster.

If this is correct diagnosis, perhaps we need to switch over
to a parse-on-first-use approach rather than on startup

Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|