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Re: [Xen-devel] Memory allocation with rebooted HVM

On 11/10/2009 21:54, "John" <lists.xen@xxxxxxxxxxxxxxxxxx> wrote:

> Is there a known bug in xen-unstable with rebooting of HVMs w/stubdom, and
> having the new domU come up before the old domU has been shut down and its
> memory fully reclaimed? I have had a couple of problems recently when
> customers rebooted their HVM domU through the OS; the last time, Xend froze,
> complaining in the log that it couldn't free up enough memory to start the
> rebooted domain. Of course, that memory should have been free, if the old
> domain had been fully shut down.

Yes. Perhaps there is a race between shutting down the stubdom and creating
the new domU? The stubdom maps a lot of the old domU's memory, and that
wouldn't get freed until the stubdom is destroyed.

> After that, Xend was unresponsive. Killing it and restarting it killed all the
> other domU's, but new ones still couldn't be created, forcing me to reboot the
> physical machine.

Odd, since it should be possible to restart just xend (but not xenstored and
other daemons) and have the system continue to work okay. Could new ones
still not be created due to lack of memory? If you use Xen's 'q' debug key,
how many domains does Xen itself think are still alive?

 -- Keir

> Unfortunately, this doesn't seem to happen every time. I'm still trying to
> determine how I can reproduce it reliably.
> -John

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