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Re: [Xen-devel] Patches for stable

On Thu, Apr 5, 2018 at 6:11 PM, Juergen Gross <jgross@xxxxxxxx> wrote:
>> Option 1: Put the RSDP in lowmem unless we know the guest will use the
>> address in start_info
>> Pro: Existing Linux instances boot
>> Con: Existing BSD instances whose memory is an exact multiple of 1 GiB
>> will have slightly slower TLB miss times.
> ... whose memory is >=1GiB ...

No, the performance benefit only applies to sections of ram that are
complete 1GiB-aligned sections.  If you have 1.75GiB, then the first
gigabyte will be a 1GiB page in the p2m (and get the performance
benefit) but the other 0.75GiB will be 2MiB aligned (and not).

We can be pedantic and nail down exactly who will get what benefit
when, but all it will do is demonstrate how limited this performance
benefit is.


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