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Date:      11 Apr 2001 10:05:53 -0400
From:      Lowell Gilbert <lowell@world.std.com>
To:        freebsd-questions@freebsd.org, oscars@mail.utexas.edu
Subject:   Re: Maxusers and max open files
Message-ID:  <44zodn351a.fsf@lowellg.ne.mediaone.net>
In-Reply-To: oscars@mail.utexas.edu's message of "9 Apr 2001 20:24:50 %2B0200"
References:  <5.0.2.1.2.20010409131651.00acad90@mail.utexas.edu>

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oscars@mail.utexas.edu (Oscar Ricardo Silva) writes:

> 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

> 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.

No, actually.  It means that if you define MAXFILES in your configuration
file, that value will override the one calculated from NPROC.  Also note
that maxfiles (and several related values) can now be adjusted dynamically
at runtime, via a sysctl(8).  A quick check of the history of the man page
for sysctl makes me think this was the case in 4.0 also.

>                                                  At the same time, I don't 
> want to place to much overhead on the machine to where it becomes unusable.

Very wise, although a maxusers setting of 128 is still well short of
causing that sort of problem.

> Any thoughts on what the usable limit is for MAXUSERS?  

I'm sorry not to offer more help, but I'm afraid that it really depends on
your application mix.  This sort of thing is generally determined by trial
and error.  It seems that running out of file slots is your *only*
problem, so some judicious experiments with adjusting those dynamically
will probably tune your system quite well.

Good luck.

 - Lowell Gilbert
-- 
Everything you know is wrong -- but some of it is a useful approximation!

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