[libvirt] Horrible performance of virDomainGetInfo()

[Jiri Denemark]

On Wed, Dec 07, 2011 at 18:20:16 +0000, Daniel P. Berrange wrote:
> On Wed, Dec 07, 2011 at 03:45:10PM +0100, Jiri Denemark wrote:
> > On Wed, Dec 07, 2011 at 14:30:10 +0000, Daniel P. Berrange wrote:
> > > While investigating the RPC problems I've noticed that we have had a
> > > huge performance regression for virDomainGetInfo() due to the change
> > > which makes virDomainEndJob() save the XML status file every time it
> > > is called.
> > > 
> > > Previous to this change, 2000 calls to virDomainGetInfo() took ~2.5 seconds
> > > 
> > > After this change, 2000 calls to virDomainGetInfo() take 2 *minutes* 45 secs
> > > 
> > > I don't have an answer right now and it shouldnt block the release, but we
> > > have todo something to avoid this overhead.
> > 
> > I think we could change job APIs to only save XML status if async job is
> > active since we are currently not really interested in other jobs anyway.
> 
> Ok, that sounds like a reasonable idea. Could you cook up a patch for
> that.

Oops, this completely slipped my mind. The fix seems to be a bit more
complicated since async job is not the only one we are interested in. I'll
send it to the list next week once I test that it didn't break anything.

Jirka