Subject: Re: bufpages
To: Tom T. Thai <>
From: Greg Wohletz <greg@duke.CS.UNLV.EDU>
List: current-users
Date: 06/24/1998 17:09:13
>On Tue, 2 Jun 1998, Jukka Marin wrote:
>> I want to improve performance of a largish news server which has 80 MB
>> of RAM.  According to options(4), I have to set options NBUF and/or
>> BUFPAGES.  However, there is no information of the range of these
>> constants - not even in the sample kerne config files.
> I'm building a NetBSD 1.3.2 kernel.  How should I set these constants?
>maxusers        200             # estimated number of users
>options         NMBCLUSTERS=4096
>options         BUFPAGES=4096   # 16MB for disk buffering
>options         NBUF=4096

What are the limitations for these paramters?  On one of our fileservers
that has 32meg of ram, if I set BUFPGES/NBUF > 1024 it panics during
autoconfig (pmap_pte returns null causing a ``ptdi'' panic in
arch/i386/i386/pmap.c).  Is there a maximum ratio of BUFPAGES to real mem?

Also, are any statistics kept by the kernel that I can query on the
effectiveness of the disk buffer cache?