Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!ames!xanth!mcnc!uvaarpa!virginia!kesmai!kff
From: kff@kesmai.COM (Kelton Flinn)
Newsgroups: comp.sys.mac
Subject: Re: Virtual Memory and hard disk life
Summary: Thrashing
Keywords: Virtual Memory
Message-ID: <218@kesmai.COM>
Date: 17 Jun 89 00:06:24 GMT
References: <13548@ut-emx.UUCP> <109873@sun.Eng.Sun.COM>
Organization: Kesmai Corporation, Charlottesville, VA
Lines: 23

In article <109873@sun.Eng.Sun.COM>, landman%hanami@Sun.COM (Howard A. Landman) writes:
> In article <13548@ut-emx.UUCP> osmigo@ut-emx.UUCP writes:
> >It seems to me that if you used Virtual Memory as your "standard, everyday
> >setup," it would involve INSTENSE, CONTINUOUS hard disk accessing, in contrast
> >to the occasional "chirp" of the drive we now experience.
> 
> No, it only involves disk accessing when you want to read or write something
> and it's not in memory.  That means a "page fault".  With enough memory, or a
> program that doesn't really use all the memory it has allocated, you just
> don't page fault that often.

   Actually, this same thought first occurred to me as I listened to the
disk drive rumbling, when I switched from MPW to Versaterm for the
first time. Unlike our MicroVax, the Mac does seem to thrash a LOT when
you switch from one large task to another. I have 2 Mb of memory, about
enough to hold 1 1/2 applications. Obviously having Virtual is better than
not being able to run SADE and MPW at the same time at all! But it does
grind more than I had hoped...
    Kelton
P.S. A warning: Never run MS Word under Virtual under the Finder. It
seems to want to initialize all 8 Mb of memory, and then checks
it periodically. It took me 15 minutes just to get out! Beleive them
when they say use MultiFinder.