Path: utzoo!utgpu!water!watmath!clyde!att!ttrdc!levy
From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: comp.unix.wizards
Subject: Re: When did paging get into System V
Message-ID: <2662@ttrdc.UUCP>
Date: 13 May 88 23:32:22 GMT
References: <53@lazlo.UUCP> <142700033@occrsh.ATT.COM> <651@pyuxe.UUCP> <7878@brl-smoke.ARPA>
Organization: AT&T, Skokie, IL
Lines: 26

In article <7878@brl-smoke.ARPA>, gwyn@brl-smoke.ARPA (Doug Gwyn ) writes:
# In article <382@cloud9.UUCP> bob@cloud9.UUCP (Bob Toxen) writes:
# >About five years after Berkeley came out with it!
# 
# So?  Performance tests showed no significant performance advantage of
# demand paging over the then-current UNIX System V scheme of partial
# swapping.  It was not until the additional advantages of an organized
# scheme like the UNIX System V region-oriented approach became apparent
# (e.g. shared libraries) that there was reason enough to implement it.
# Conversations I've had with kernel implementors indicate that, modulo
# a few glitches that can be readily corrected, the UNIX System V scheme
# (which resembles VMS's) is on the right track, and that Babaoglu's
# scheme embedded in 4BSD often has to be totally replaced.  (Sun
# designed their original memory management hardware to look virtually
# the same as the VAX's, to avoid this.  Not everyone has had that option.)

There is one very nice thing about SV paging (over swapping) that I have
noticed on 3B2 hardware:  very large executables start up almost instantly
instead of taking many seconds to load.  I don't know whether this
differential is true for Berkeley or not, or on VAXen, never having used
a non-paging Berkeley, or VAX UNIX system.  Wizards?
-- 
|------------Dan Levy------------|  Path: ihnp4,<most AT&T machines>!ttrdc!levy
|              AT&T              |  Weinberg's Principle:  An expert is a
|       Data Systems Group       |  person who avoids the small errors while
|--------Skokie, Illinois--------|  sweeping on to the grand fallacy.