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From: jlg@lanl.ARPA (Jim Giles)
Newsgroups: net.arch
Subject: Re: paging and loading
Message-ID: <7963@lanl.ARPA>
Date: Thu, 25-Sep-86 14:08:03 EDT
Article-I.D.: lanl.7963
Posted: Thu Sep 25 14:08:03 1986
Date-Received: Fri, 26-Sep-86 00:57:13 EDT
References: <832@hou2b.UUCP> <389@cci632.UUCP>
Reply-To: jlg@a.UUCP (Jim Giles)
Organization: Los Alamos National Laboratory
Lines: 20

In article <389@cci632.UUCP> rb@ccird1.UUCP (Rex Ballard) writes:
>Most applications spend 90% of their time executing only 10% of their
>code.  Interactive and transaction processing applications spend
>nearly 95% of their time in a "wait for I/O, parse, loop" with an
>occaisional "do special purpose 'case' processing".  There are more
>than a few stories of such applications where swapping that involved
>a loop smaller than 2K caused serious degradation due to the 64K to
>1Mb "tails" that would get swapped in with them.
>
I've seen codes that spend 99% of their time in just 1-2% of the code.
So what?  The code only occupies 2% of the memory image of the program.
The rest of the memory image is data, and 90% of it is being processed
repeatedly by that tight loop in the code.

Yes, when you job mix is composed mainly of small and/or interactive
processes, by all means you should have a VM system.  I question the
need for VM in contexts where this is not true.

J. Giles
Los Alamos