Re: [Xen-users] How to detect a domain shutdown with as less overheadas possible?

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Kip Macy wrote:

> In tools/python/xen/xend/XendDomain.py you'll see that reap is called
> by onVirq which in turn is a handler registered for xend.virq.
> xend.virq is an event-channel used by xend for notifications. It is
> set up in tools/python/xen/xend/server/channel.py. In -testing reap
> appears to be called as soon as a domain crashes, meaning that
> everything is working as it should. In -unstable a guest doesn't get
> reaped until 'xm list' gets called awakening xend to the fact that it
> has work to do.
>  
There's a bug under bugzilla (#7) about this.  It appears xcs is not 
delivering VIRQs properly.
The DOM_EXC virq won't be delivered for every possible shutdown case 
either.  It's delivered for a crash or for a shutdown (a domain 
initiated shutdown) but not for a domain destroy.
I've found the best way to detect shutdown reliably is with a polling 
loop.  There's code in xenctld to do just this (and I believe Mike Wray 
is doing this too in the new Xend).
I've done performance testing with querying every 2 seconds and the 
overhead is trivial.
As Mark mentioned, there is an event socket for Xend.  Be warned though 
that right now, those event are probably not very reliable.
If you're looking for a cheap solution that can be done with the shell, 
I'd suggesting grabbing VM-Tools and using the vm-list command to query 
the flags of a domain.  It will have significantly less overhead than xm 
list.
Regards,
Anthony Liguori

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users