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RE: [Xen-devel] [RFC][PATCH] 0/9 Populate-on-demand memory

To: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Subject: RE: [Xen-devel] [RFC][PATCH] 0/9 Populate-on-demand memory
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Wed, 24 Dec 2008 07:35:11 -0800 (PST)
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> We could to allocate a new page at that point; but it's likely that
> the allocation will fail unless there happens to be memory lying
> around somewhere, not used by dom0 or any other doamin.  And if that
> were the case, why not just start it with that much memory to begin
> with?

Actually, if dom0_mem is used rather than the default of letting
domain0 absorb all free memory and dole it as needed to launching
VMs, there will almost always be some memory lying around.

And in the not-to-distant future, when live migration is
more widely used, there had better be memory lying around
or migration won't work.

As for "why not just start it with that much memory to begin
with?"... because in most environments VMs are sized once
(e.g. 512MB) and almost never changed... because sysadmins
rarely want to be bothered with constantly fine tuning
just to use an extra spare few MB of memory.

That's why your patch is so important!


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