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From: John Dyson <dyson@dyson.iquest.net>
Message-Id: <199612101919.OAA00466@dyson.iquest.net>
Subject: Re: Multiple Buffer allocation of Shared Memory
To: terry@lambert.org (Terry Lambert)
Date: Tue, 10 Dec 1996 14:19:26 -0500 (EST)
Cc: scrappy@hub.org, hackers@FreeBSD.ORG
In-Reply-To: <199612101803.LAA04496@phaeton.artisoft.com> from "Terry Lambert" at Dec 10, 96 11:03:25 am
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> 
> Administrative limit because of address space crowding... just like
> the limit on segment size.  You can override as necessary, and
> rebuild a kernel.  However, I would suggest you use mmap instead,
> if possible.
> 
SYSVSHM isn't that different from mmap, but it has a different namespace.

> 
> It would be much better to mmap a contiguous area, where each message
> fills up exactly 4k (even if you need pad to do it) and make sure the
> messages are on 4k boundries to ensure seperate protection domains.
> This is true, even if you use SVR4 primitives...
> 
I agree with this -- the larger the number of seperate mappings, the
more OS overhead there will be.

John