object-based rmap and pte-highmem

[Martin J. Bligh]

> So whole stole the remaining 1.85 seconds?   Looks like pte_highmem.

I have a plan for that (UKVA) ... we reserve a per-process area with 
kernel type protections (either at the top of user space, changing
permissions appropriately, or inside kernel space, changing per-process
vs global appropriately). 

This area is permanently mapped into each process, so that there's no
kmap_atomic / tlb_flush_one overhead ... it's highmem backed still.
In order to do fork efficiently, we may need space for 2 sets of 
pagetables (12Mb on PAE).

Dave McCracken had an earlier implementation of that, but we never saw
an improvement (quite possibly because the fork double-space wasn't
there) - Dave Hansen is now trying to get something work with current
kernels ... will let you know.

M.