Does anyone know the history behind pmap_extract?  

I have been looking through the 4.4 daemon book and that routine was never
mentioned.  In fact, it states that the pmap module is free to discard any
mapping information about non-wired pages at any time.  

On the other hand, the vm sources use pmap_extract in several places to
get information about virtual-to-physical mappings.  I don't understand
why the vm system does that because that's precisely what the vm system
was designed to track.

At the moment it seems as if ports either have standard forward-mapped mmu
tables in hardware or emulate them in software.  This seems redundant to
me, and I think it will cause problems when moving to a full 64-bit (or at
least the current 40-bit) VAs.  

=========================================================================
Eduardo Horvath				eeh@btr.com
"Cliffs are for climbing.  That's why God invented grappling hooks."
					- Benton Frasier