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

To: "Tim Deegan" <Tim.Deegan@xxxxxxxxxx>
Subject: Re: [Xen-devel] pre-reservation of memory for domain creation
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Tue, 09 Feb 2010 12:41:05 +0000
Cc: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>
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>>> Tim Deegan <Tim.Deegan@xxxxxxxxxx> 09.02.10 12:34 >>>
>At 11:21 +0000 on 09 Feb (1265714487), Jan Beulich wrote:
>> The Xen crash was what Keir talked about; I was referring to the
>> increased early allocation which continues to be out of sync with the
>> ballooning happening in the tools (and hence in environments where
>> ballooning is being used likely has no chance of succeeding).
>
>OK; the early allocation, for a domain with no vcpus and no RAM, is a
>constant 4 MiB, and just needs to be added to whatever overheads are
>already being taken into account (domain and vcpu structs, VMCBs, &c).

The issue is that this used to be 1Mb. Hence the question whether
in fact it needs to be 4Mb now (which it got increased to when max
HVM vCPU-s got grown to 128). And if indeed the increase was
necessary, then to make it depend on the number of vCPU-s the
VM will actually have (hence the question on how much memory is
needed at this stage per vCPU).

The point here is that on one hand there's no clear picture how
much memory is really needed before the full shadow allocation
gets set up, and on the other hand Keir is recalling issues
resulting from not growing the amount to 4Mb.

Jan


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