Re: Strange (???) xl behavior for save, migrate and migrate-receive

[Olaf Hering <olaf@aepfle.de>]

On Mon, Oct 17, Daniel Kiper wrote:

> During work on memory hotplug for Xen I have received some notices
> that it breaks machine migration. I had some time and I done some
> tests a few days ago. It looks that source of this problem is
> xl command itself. I discovered that generic save/restore mechanism
> is used for machine migration. xl save store machine config which
> was used at machine startup with current machine state. It means
> that it does not take into account any config changes which were made
> during machine run. This behavior does not allow migrating domain,
> on which memory hotplug was used, to restore on destination host
> because current size of memory allocated for machine is larger than
> size of memory allocated at startup by memory option. Yes, it is
> memory option not maxmem option. However, it is not important here
> because I think that generic behavior of xl save, migrate and migrate-receive
> should be changed (fix for memory hotplug case is workaround for the
> generic problem which will return sooner or later). I think that xl save,
> migrate and migrate-receive should use current machine state and __CURRENT__
> config (from xenstore ???) to do their tasks. However, I am aware that
> this change could have large impact on current users. That is why I decided
> to ask you about your opinion and suggested solutions in that case
> (in general not memory hotplug only).

Its easy to implement in xl by throwing some xenstore watches into the
code.

http://lists.xensource.com/archives/html/xen-devel/2011-10/msg00778.html

Olaf