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Re: [Xen-devel] HVM and free_memory query
On 09/07/2009 20:28, "Apoorva Kulkarni" <apoorva@xxxxxxxxx> wrote:
> #xm list
> Name ID Mem VCPUs State
> Domain-0 0 512 1 r----- 25251.4
> controller 1 512 1 -b---- 39948.6
> vm.windows03 44 30720 1 r----- 22.0
> As you can see, the free_memory shown is 337M which is a good 241M less than
> what it should have been (31298M - 30720M = 578M) after the Windows VM was
> created. My question here is where/why does xen use that extra 241M. Any
> pointers much appreciated.
It's used for shadow pagetables and other memory book-keeping structures.
This reservation is sized as a fraction of the domain's configured memory
allocation -- the fraction is just under 0.8%. And 0.8% of 30720MB is 245MB,
so that works out just about right.
This is one of those cases where a small fraction of a very big number is
still a big number. ;-)
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