Subject: Re: Accounting for differences in physical memory performance
To: Jason R Thorpe <>
From: Ken Seefried <>
List: tech-kern
Date: 05/22/2002 22:27:55
Thanks Jason.  Is there any doco that explains how this works, or can you 
point me to a source file to plow through? 


Jason R Thorpe writes: 

> On Thu, May 16, 2002 at 02:27:17AM +0000, Ken Seefried wrote: 
>  > Is there a way, implimented or theoretical, that would maximize the 
>  > performance of systems with different physical memory performance 
>  > characteristics?  
> Yes, NetBSD currently has a way to handle this (I added it a couple
> of years ago). 
> What it does is break up the memory into multiple free lists, sorted in
> order of descending priority.  The way this is used is that you would put
> your fastest memory on freelist 0, next fastest on freelist 1, and so on. 
> The mvme68k port currently uses this facility for VME expansion memory. 
> It's not perfect (in particular, if a process gets stuck with a crappy
> page, it could wind up using it for quite some time), but it seems to
> be pretty effective at minimizing the bad effects. 
> -- 
>         -- Jason R. Thorpe <>