Re: [Lse-tech] Re: 10.31 second kernel compile

[David S. Miller]

   From: Paul Mackerras <[e-mail]>
   Date: Sat, 16 Mar 2002 22:55:40 +1100 (EST)
   
   IMHO it would be interesting to compare the size and complexity of
   using a hash table for the page tables with a 5-level tree.  For a
   32-bit address space I think the tree wins hands down but for a full
   64-bit address space I am not convinced either way at present.

You only need a 4-level tree for a full 64-bit address space as long
as you can guarentee less than (32 + PAGE_SHIFT) bits of physical
addressing (ie. you can use 32-bit pmd_t's and pgd_t's in that case).

At least this is how I remember the numbers working out.