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

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> if Balloon driver is not present in the guest OS then how xen control
> the memory of the that Guest OS

It can't; Xen depends on guest OS co-operation in order to resize the guest's 
physical memory footprint.

> 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 
be controlled within the guest by echoing something into a special file.  If 
there's no balloon driver, there's no way to change the memory footprint (as 
of 3.1 the balloon driver can work in HVM, though).

Other hypervisors / virtual machine software is able to page guest memory out 
to disk in order to vary the machine RAM allocation used by each guest; Xen 
doesn't do this.

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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