From owner-freebsd-questions  Mon Apr  9 11:24:40 2001
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Date: Mon, 09 Apr 2001 13:22:59 -0500
To: questions@freebsd.org
From: Oscar Ricardo Silva <oscars@mail.utexas.edu>
Subject: Maxusers and max open files
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I know that the max number of open files is related to the maxusers number 
in the kernel config file.  /usr/src/sys/conf/param.c indicates:

#define NPROC (20 + 16 * MAXUSERS)
#ifndef MAXFILES
#define MAXFILES (NPROC*2)
#endif
int     maxproc = NPROC;                        /* maximum # of processes */
int     maxprocperuid = NPROC-1;                /* maximum # of processes 
per user */
int     maxfiles = MAXFILES;                    /* system wide open files 
limit */
int     maxfilesperproc = MAXFILES;             /* per-process open files 
limit */

So, that means that if I want to raise the max number of open files, I need 
to change MAXUSERS in the kernel and recompile.  At the same time, I don't 
want to place to much overhead on the machine to where it becomes unusable.

Any thoughts on what the usable limit is for MAXUSERS?  The machine I'm 
asking about is currently running FreeBSD 4.0. acting as a dns cache server 
for our campus (approx. 50,000 hosts) and is running djbdns-1.05.  We had 
problems this weekend where the dnscache portion of the djbdns package 
reported that it could not open more files.  I would like to raise the 
number (currently, max number of open files set to 4136, maxusers 128) but 
don't want to suffer to much of a performance hit.

I've tried looking for more information on open files and max number of 
open files but have only found one or two sentences in the FreeBSD 
handbook.  Any other resources for this kind of information?  I found the 
piece of code above but admit that I'm not a programmer.

Any information would be extremely appreciated.


Oscar


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