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[Xen-devel] pre-reservation of memory for domain creation

To: <dongxiao.xu@xxxxxxxxx>
Subject: [Xen-devel] pre-reservation of memory for domain creation
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Tue, 12 Jan 2010 14:47:32 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
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Close to the top of XendDomainInfo::_constructDomain() there's a
comment

        # Hack to pre-reserve some memory for initial domain creation.
        # There is an implicit memory overhead for any domain creation. This
        # overhead is greater for some types of domain than others. For
        # example, an x86 HVM domain will have a default shadow-pagetable
        # allocation of 1MB. We free up 4MB here to be on the safe side.
        # 2MB memory allocation was not enough in some cases, so it's 4MB now

which would seem inconsistent with the current implementation in the
hypervisor: sh_set_allocation() as called from shadow_enable() wants
*at least* 4Mb - modified from 1Mb by c/s 20389. It is not clear (to me)
from the changeset description why this change was needed (and even
less why it was needed uniformly for 64- and 32-bits). If indeed it is
needed, the tools should be adjusted accordingly.

Jan


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