PAE question

[Aviv Greenberg]

I think that the reason for installing PAE kernel as a default is
because the No Execute (aka NX bit) CPU feature is available only when
the CPU is configured to PAE mode. AFAIK the other OS from Redmond
also uses PAE by default (using the ntkrpamp image).

I don't know about performance implication of PAE, but i assume it is
minimal: It is supported by the CPU HW. When PTE is ebabled, the CPU
page tables are changed slightly to support a bigger address space.
The difference is in the PGD and PTE structures (IIRC there is another
middle PMD struct when in PAE mode). All the page table entries are
cached by using the TLB, so you should not see any real performance
difference.

Also, i don't think going x64 will improve anything (especially if you
dont really need a 64 bit address space) - it will only make your
programs consume more RAM.

On Sun, Aug 2, 2009 at 23:46, Oron Peled<oron at actcom.co.il> wrote:
> On 02.08.2009 Hetz Ben Hamo wrote:
>> The Fedora 11 default installation installs the kernel with PAE
>> installation *regardless* of how much RAM I have.
>>
>> I was wondering: are there any performance "penalties" when using PAE
>> enabled kernel instead of the i686 version?
>
> Two links with some more reasoning/info:
> http://thorstenl.blogspot.com/2009/05/fedora-11-kernel-pae-and-what-it-
> means.html
>  https://fedoraproject.org/wiki/Features/ArchitectureSupport
>
> --
> Oron Peled                                 Voice: +972-4-8228492
> oron at actcom.co.il                  http://users.actcom.co.il/~oron
> ... Complex problems have simple, easy to understand wrong answers.
>
>
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