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Re: [Xen-devel] [PATCH v3 1/3] libxl: xl mem-max et consortes must update static-max in xenstore too [and 1 more messages]

On Thu, Apr 11, 2013 at 11:15:15AM +0100, George Dunlap wrote:
> On Wed, Apr 10, 2013 at 4:56 PM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> 
> wrote:
> > Daniel Kiper writes ("Re: [Xen-devel] [PATCH v3 3/3] xl: Improve xl 
> > documentation in regards to guest memory management"):
> >> No, memory hotplug should not change "static maximum" in any case.
> >
> > Why shouldn't it ?
> FWIW, at least XenServer uses "static max" to mean "cannot be changed
> except by rebooting".  It *also* uses *that* for HVM guests to say
> "how much memory to advertize to the guest".  That is, if you boot a
> VM with memory = X and static_max = Y, then it will put Y amount of
> memory in the virtual e820 map, allocate X memory for the PoD, and
> then rely on the balloon driver to balloon from Y down to X during
> boot.
> This is two slightly different meanings -- "how much to put in the
> guest e820" and "how much maximum a guest is ever allowed to have".
> The plain meaning of "static max" should be the second (i.e., can't be
> changed dynamically at run time).  If we want a "max in the e820 at
> build time" we should probably come up with a new term; and if "how
> much the guest is ever allowed to have without rebooting" is not a
> useful concept, we should probably just discard it.

George, thanks for this clarification.


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