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Is there a reason to give a VM a round base-2 amount (2048MB, 4096MB, etc) of memory?

14

The title pretty much says it all, is there any advantage to giving a VM 2048MB of memory instead of rounding to base-10 and doing 2000MB?

2 Answers

4

The physical memory in the server is a multiple of a power of two, so it will slice evenly if you use other multiples. There may be some incredibly minor improvements with SLAT and such if they're properly aligned too. Otherwise no.

3

Hyper-V internally allocates memory in 2MB chunks. The hypervisor itself will use 2MB page table entries for efficiency, if possible, if your processor supports Second-Level Address Translation (SLAT.) This will be possible for pretty much any VM with Dynamic Memory turned off.

Other than that, no it doesn't matter.


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Is there a reason to give a VM a round base-2 amount (2048MB, 4096MB, etc) of memory?

14

The title pretty much says it all, is there any advantage to giving a VM 2048MB of memory instead of rounding to base-10 and doing 2000MB?


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9

The physical memory in the server is a multiple of a power of two, so it will slice evenly if you use other multiples. There may be some incredibly minor improvements with SLAT and such if they're properly aligned too. Otherwise no.

edit

@poige As best I know, yep, no issues... We'd really need someone who know SLAT (et alii) inside and out for a definitive answer. - Chris S Apr 9, 2012 at 2:16

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