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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.works
Subject: Re: WORKS Digest   V4 #1
Message-ID: <3446@utzoo.UUCP>
Date: Fri, 6-Jan-84 17:39:01 EST
Article-I.D.: utzoo.3446
Posted: Fri Jan  6 17:39:01 1984
Date-Received: Fri, 6-Jan-84 17:39:01 EST
References: <15014@sri-arpa.UUCP>
Organization: U of Toronto Zoology
Lines: 21

"I guess you mean that a demand-paging virtual memory system is de
facto "more powerful" than a smart, automatic segment-swapping system
you'd rather not try to implement.  An anticipatory scheme of this
sort is even MORE powerful than dp-vm, and requires no extra hardware,
only a non-trivial software development environment, some work, and an
open mind."

There is only one real problem with anticipatory virtual-memory
schemes.  (Note that I am addressing anticipatory-vs-demand issues
*without* attempting to address segments-vs-pages issues.)  The only
ones I'm aware of that actually got *implemented* didn't work nearly
as well as demand strategies.  I am not up on recent work in this area;
perhaps the millenium has arrived.  But the last I heard was a general
conclusion that it is ***NOT*** easy to anticipate the program's demands
well enough to get any large advantage out of it.

(Please do not cite the awesome calculated performance of wonderful
strategy X as a rebuttal; real results on real loads only, please.)
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry