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From: sameer <sameer@c2.net>
Message-Id: <199612132205.OAA00366@blacklodge.c2.net>
Subject: Re: getdtablesize, OPEN_MAX, and sysctl
To: bde@zeta.org.au (Bruce Evans)
Date: Fri, 13 Dec 1996 14:05:02 -0800 (PST)
Cc: freebsd-hackers@FreeBSD.ORG, freebsd-questions@FreeBSD.ORG, sameer@c2.net
In-Reply-To: <199612130854.TAA26648@godzilla.zeta.org.au> from Bruce Evans at "Dec 13, 96 07:54:23 pm"
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> >	So I have a machine (2.1-STABLE) with OPEN_MAX set to 256.
> >When I do sysctl -a kern.maxfiles is 2088. Is there a relationship
> >between OPEN_MAX and something that shows up in sysctl?
> 
> No.  OPEN_MAX is broken and should never be used.  It is currently
> used in /usr/src only to configure the number of descriptors for the
> for the init process.  This value is inherited by child processes.

	By OPEN_MAX I am referring to the 

options OPEN_MAX=XX

	in the kernel config file. I thought that OPEN_MAX was the
thing to use for setting max # of fds in your kernel. If that isn't
it, what should I use?

> >	On the last two machines, the select runs fine On the first
> >two, the select (the result of the getdtablesize() is going to the
> >first arg of the select() call) returns EINVAL.
> 
> select() only supports a fixed maximum number of descriptors in
> -stable.  The default is FD_SETSIZE = 256.  2.2 and -current support
> any reasonable number provided the application is compiled with
> FD_SETSIZE defined as a larger number.
> 

	I'm pretty sure this is the problem. Are you saying that on
2.1-stable you can't do a select on more than 256 fds, and on 2.2 and
-current you can do a select on more than 256 fds but you need to make
sure you #define FD_SETSIZE first?

-- 
Sameer Parekh					Voice:   510-986-8770
President					FAX:     510-986-8777
C2Net
http://www.c2.net/				sameer@c2.net