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RE: [Xen-devel] [PATCH] PoD: Handle operations properly when domain is d

To: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] PoD: Handle operations properly when domain is dying
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Wed, 11 Nov 2009 09:58:50 -0800 (PST)
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Thanks for the detailed explanation.  I think
"Populate on Demand" connotes too much like
"Copy on Write" and doesn't really describe
the essence of what is going on: Booting pre-ballooned.
Thus my confusion.

> If this pre-allocated amount of RAM is used up, no
> more memory is allocated; the domain crashes.

This is of course less than ideal as it ensures that
administrators will choose some safe (probably fairly large)
amount of memory, a significant portion of which will often
be wasted.  But I suppose its better than the (much larger)

> So if you're using PoD, you can trust that the memory used by the VM 
> will not change "under your feet" so to speak.

That answers my question then.

The problem still applies to ballooning... at least in Linux
there are ways that a guest sysadmin can manually adjust
the balloon without tools knowledge.  But I guess that's
a different discussion.

Thanks again,

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