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

> I've just finished a simple Perl script that brings out a 
> whole domain from a directory (with a small config file and 
> some <device>.gz files), create Logical Volumes with each 
> device, starts the domain, wait for the domain to shutdown, 
> push back into the *.gz the content of the LVs and remove 
> them. This is quite handy to launch any test machine stored 
> on the NFS server on one of our Xenified hosts.

> My problem is the overhead of checking for the domain to shut 
> down as I intend to use the domUs not only for functional 
> testing but also to have a good guess of the performance we 
> can get on real hardware (with only one domU / real host).

We should introduce a call-out for domain exits. Kip's looking core
dumps, so I guess he's addressing this.

> After xm create, this script regularly calls :
> xm domid "domainname"
> The problem is that this check eats a small chunk of CPU 
> time: it takes
> 0.2 - 0.3s of real CPU time on each call. I've looked into 
> /proc/xen hoping to find the list of domains stored here, 
> allowing a simple file read or stat to give me the 
> information I need, but it seems there's nothing like this.

There's a bunch of improvements to xend waiting to be posted which will
likely help. There's certainly no good reason to be using CPU unless you
have console output active or something.

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