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From: tim@crackle.amd.com (Tim Olson)
Newsgroups: comp.unix.wizards
Subject: Re: System V Shared Memory applications
Message-ID: <24775@amdcad.AMD.COM>
Date: 9 Mar 89 01:57:38 GMT
References: <21499@shemp.CS.UCLA.EDU>
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Reply-To: tim@amd.com (Tim Olson)
Organization: Advanced Micro Devices, Inc. Sunnyvale CA
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In article <21499@shemp.CS.UCLA.EDU> brett@CS.UCLA.EDU () writes:
| I am interested in knowing if you have ANY software
| that makes use of System V's shared memory.

I'm not sure if this is the kind of thing you are looking for, but I
used shared memory to implement the communication between a "load
daemon" and the user-invokable load average reporter on an IBM RT/PC,
which didn't have the calculated load averages in the kernel.

The load daemon updated, at 1-second intervals, a circular buffer
holding the last 15 minutes worth of run-queue sizes.  The circular
buffer and its associated pointer were kept in a shared-memory segment,
so that they could be read by user-level programs to calculate load
averages.

One benefit of this is that no set-uid program is needed to read the
kernel and report load averages.


	-- Tim Olson
	Advanced Micro Devices
	(tim@amd.com)