Re: larger default page sizes...

["H. Peter Anvin" <hpa@zytor.com>]

J.C. Pizarro wrote:
> 
> But there is a general problem of larger pages in systems that
> don't support them natively (in hardware) depending in how it's
> implemented the memory manager in the kernel:
> 
>    "Doubling the soft page size implies
>       halfing the TLB soft-entries in the old hardware".
> 
>    "x4 soft page size=> 1/4 TLB soft-entries, ... and so on."
> 
> Assuming one soft double-sized page represents 2 real-sized pages,
> one replacing of one soft double-sized page implies replacing
> 2 TLB's entries containing the 2 real-sized pages.
> 
> The TLB is very small, its entries are around 24 entries aprox. in
> some processors!.
> 

That's not a problem, actually, since the TLB entries can get shuffled 
like any other (for software TLBs it's a little different, but it can be 
dealt with there too.)

The *real* problem is ABI breakage.

	-hpa