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Re: [Xen-devel] Is it possiable to use domU's balloon in dom0 user program?

> From: Ian Campbell [mailto:Ian.Campbell@xxxxxxxxxx]
> Sent: Monday, April 15, 2013 3:19 AM
> To: Demon King
> Cc: xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Is it possiable to use domU's balloon in dom0 user 
> program?
> On Sat, 2013-04-13 at 11:21 +0100, Demon King wrote:
> > Our team want designed a program in dom0 to control vm's memory
> > through balloon, such as to increasing balloon memery of vm1 and then
> > other vm will use it later. Is it possiable to do this?Thank you!
> I'm not 100% what you are asking but if you are asking if you can reduce
> a domain's memory with ballooning and the subsequently (either
> immediately or later) increase the memory allocation of another domain
> using that slack memory then the answer is yes.
> The only constraint is that in the absence of memory hotplug (which is
> present in mainline kernels but not AFAIK support yet by most
> toolstacks) you cannot balloon a guest up to more than its original
> memmax= value, note that it is possible to boot a PV domain with less
> current allocation than its maxmem ("preballooned") and using PoD and
> suitable PV drivers the same can be done with some types of HVM guest.

Any chance you are trying to do what xenballoond does?  See
the source tree under tools/xenballoon (or google "xenballoond.README").
Note that this code is five years old, is distro dependent, and is now
completely unsupported.  It was the first step toward transcendent
memory, which has replaced it.

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