Andrew Morton wrote:
> Linus Torvalds <torvalds@osdl.org> wrote:
> 
>>
>>
>>On Tue, 16 Nov 2004, David Howells wrote:
>>
>>>Do you have any objection to compound pages being made mandatory, even without
>>>HUGETLB support?
>>
>>I haven't really looked into it, so I cannot make an informed decision.  
>>How big is the overhead? And what's the _point_, since we don't seem to 
>>need them normally, but the code is there for people who _do_ need them? 
> 
> 
> Yes, it's just the single pointer chase.  Probably that's the common case
> now, because everyone will be enabling hugepages on lots of architectures.
> 
> But still, the non-compound code is well tested too, and leaving it in
> place does make a little microoptimisation available to those who want it,
> so I don't see a reason yet to make compound pages compulsory.
> 
> So I'd suggest that we make compound pages conditional on a new
> CONFIG_COMPOUND_PAGE and make that equal to HUGETLB_PAGE || !MMU.

Good idea. BTW, any reason why the following (very)micro optimisation
shouldn't go in?

It currently only picks up a couple of things under fs/, but might help
reduce other ifdefery around the place. For example mm.h: page_count and
get_page.