Re: CVS commit: src/sys/uvm

["Toru Nishimura" <locore64%alkyltechnology.com@localhost>]

Matt Thomas modified UVM colour matching scheme;

> Modified Files:
>        src/sys/uvm: uvm_extern.h uvm_fault.c uvm_km.c uvm_page.c
>
> Log Message:
> Add better color matching selecting free pages.  KM pages will now allocated
> so that VA and PA have the same color.  On a page fault, choose a physical
> page that has the same color as the virtual address.

This change is a big forward-reap to have VIPT-safe NetBSD VM for R4000 and
modern ARM.  Combined with matched KVA selection against UVA, found in
vm_machdep.c::vmapbuf(), there remains little ocasion where VM chooses
mistakenly wrong colour combination to bind VPN and PFN.

The entire effect is to eliminate the necessity of VIPT fixup efforts in 
port-specific
pmap.c and ends up with improving the cache effeciency in large degree.  This
is _the intent_behind VIPT design.  So far OS virtual memory strategy paid 
little
attention to make VIPT cache work correctly.

Toru Nishimura / ALKYL Technology