Re: [PATCH 03/10] x86, mm: get early page table from BRK

[Yinghai Lu]

On Wed, Oct 10, 2012 at 7:17 AM, Konrad Rzeszutek Wilk
<konrad@xxxxxxxxxx> wrote:
> On Tue, Oct 09, 2012 at 06:03:33PM -0700, Yinghai Lu wrote:

>> good point, i add one line comment to the revised patch.
>>
>> +/* need 3 4k for initial PMD_SIZE, 4k for 0-ISA_END_ADDRESS */
>
> Can you explain the math please? It sounds like this is based on
> the assumption that this you are using huge pages. But what if you
> are not? What if you can only do 4KB pages?

yes that is some extreme case:
assume that 2M range is [2T-2M, 2T),
one page for PGD-[2T-512g, 2T), one for PUD - [2T-1G, 2T), and one for
PMD -: [2T-2M, 2T)
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