Subject: Re: vm_mmap: pmap botch! / mb_map full
To: None <port-sparc@NetBSD.ORG, D.K.Brownlee@city.ac.uk>
From: Paul Kranenburg <pk@cs.few.eur.nl>
List: port-sparc
Date: 06/13/1995 13:12:40
> 	I keep getting 'pmap botch!'

This happens when a process requests a file to be mmap'ed at a fixed address
- either explicitly by using MAP_FIXED or implicitly because of a execve() -
while that file is already mapped at another virtual address (somewhere,
maybe in another process) which is not congruent modulo the cache distance.

It would interesting to know what processes are running at the time you
get the `botch' and what triggers it (e.g. the program you're starting).

Note that while `pmap_prefer()' eliminates a lot of unwanted cache aliasing
it does not work in all circumstances. Fixing this will probably require
changes to the MI VM code.

-pk