Re: [Xen-devel] ballon driver interaction with native page allocator.

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > It can't; Xen depends on guest OS co-operation in order to resize the
> > guest's physical memory footprint.
>
> ok it means if during domU creation if config file says memory is 64MB
> then it can't be resize.

As long as the guest has the balloon driver, then you can change the memory 
allocation using the command line tools in dom0 (or the domain can 
voluntarily change its allocation).

> > > or there is some other mechanism also with which the guest OS page
> > > allocator can inftate or deflate the balloon.
> >
> > The balloon can be controlled from outside Xen using xm mem-set.  It can
> > also
>
> outside xen means guest OS can use xm-mem set tool to inflate and
> deflate the ballon.

xm mem-set is run in dom0 and sends messages to the guest, telling it to 
change its memory footprint (and by how much).

> I think so many control for the ballon driver may cause the conflit if
> xen and guest OS is simultaneously trying to resize the ballon.

Correct - it does cause problems.  It won't crash, or anything nasty like 
that.  But if the guest does a voluntary resize on its balloon then the dom0 
tools won't know about it, and may get confused about the current memory size 
of the domain.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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