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

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> 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.

Nice.
 
> 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.
Ian

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