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From: idall@augean.OZ (Ian Dall)
Newsgroups: comp.unix.wizards
Subject: Re: When did paging get into System V
Message-ID: <331@augean.OZ>
Date: 19 May 88 08:36:26 GMT
References: <53@lazlo.UUCP> <142700033@occrsh.ATT.COM> <651@pyuxe.UUCP> <7878@brl-smoke.ARPA> <2934@ihlpe.ATT.COM> <7896@brl-smoke.ARPA>
Reply-To: idall@augean.OZ (Ian Dall)
Organization: Engineering Faculty, University of Adelaide, Australia
Lines: 36

In article <7896@brl-smoke.ARPA> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
>In article <2934@ihlpe.ATT.COM> daryl@ihlpe.ATT.COM (Daryl Monge) writes:
>>Strongly depends on the problem you are trying to solve, doesn't it.
>>Never place much on performance benchmarks unless it is YOUR application
>>that is being benchmarked.
>
>Exactly right.  The test I referred to was done by USG on what
>they considered a typical application job mix among their clients.
>
.
.
.
>
>It didn't take long for people to develop hopelessly BSD-dependent
>applications, though, so it's hard to dig our way out even if we
>wanted to.

And programs are developed to suit the available system. Sometimes
what is logically one program is split into small processes communicating
though pipes and temporary files etc. If one simply transplants that to
a demand paged environment there is not likely to be much performance
gain. But if the application is rewritten as fewer larger programs with
less communication overhead there may be a performance gain.

As someone who has spent a lot of time shoe horning things into
PDP-11's 64k address space, I suspect the REAL gain in a demand paged
virtual memory system is in programmer productivity rather than
program performance. It certainly saves a lot of time not having to
worry about overlays or using temporary files etc.

If I can have a system with infinite physical memory then maybe I
wont care if its paging or not. Till then...
-- 
 Ian Dall           "In any argument there will be people on your
                     side who you wish were on the other side."
idall@augean.oz