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

David S. Miller
2002-03-18T03:11:26Z

From: Paul Mackerras <paulus@samba.org>
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.