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From: chrisp@mks.com (Chris Phillips)
Newsgroups: comp.arch
Subject: Re: Tradeoffs
Message-ID: <1990Jun8.171955.24673@mks.com>
Date: 8 Jun 90 17:19:55 GMT
References: <640@sibyl.eleceng.ua.OZ> <2662CE6C.3E68@tct.uucp> <26798@eerie.acsu.Buffalo.EDU> <266576A7.6D17@tct.uucp> <9494@pt.cs.cmu.edu> <1990Jun3.041822.13548@utzoo.uucp> <27416@eerie.acsu.Buffalo.EDU> <.5X3-ZB@xds13.ferranti.com> <671@sibyl.eleceng.ua.OZ> <13684
Reply-To: chrisp@mks.com (Chris Phillips)
Organization: Mortice Kern Systems, Waterloo, Ontario, Canada
Lines: 21

In article <136844@sun.Eng.Sun.COM> martyi@sun.UUCP (Marty Itzkowitz) writes:
>In article <671@sibyl.eleceng.ua.OZ> ian@sibyl.OZ (Ian Dall) writes:
>>
>>operating system does. So why not *let* the virtual memory operating
>>system do it? (*) Why does it matter that "ps" shows a large number for
>
>The main argument for NOT letting the virtual memory system deal with it
>is that the program has a much better idea of an appropriate strategy
>for page replacement than the OS can infer from past behavior.  When the
>user switches to a new file the editor can infer that the pages from the
>previous edit can be discarded, whereas the OS will assume that if
>they were recently used they ought to be kept.
>
>	Marty Itzkowitz

This is only an argument for better interfaces between the Virtual Memory Manager
and the programmer.  MMAP techniques and ideas from MACH allow use of VM features
without duplicating the mechanisms.

Chris Phillips
chrisp@mks.com -or- chrisp@telly.on.ca