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From: danc%sri-tsca@turtlevax.UUCP
Newsgroups: net.unix-wizards
Subject: Question on VAX Page Table Entry in 4.2BSD
Message-ID: <9162@brl-tgr.ARPA>
Date: Tue, 12-Mar-85 19:47:33 EST
Article-I.D.: brl-tgr.9162
Posted: Tue Mar 12 19:47:33 1985
Date-Received: Fri, 15-Mar-85 02:40:29 EST
Sender: news@brl-tgr.ARPA
Lines: 17

In machine/pte.h there are two fields in the VAX "struct pte" that
don't seem to be used for anything.  They are "pg_vreadm" and "pg_swapm".
From looking at vm_mem.c and vm_page.c, it seems that pg_vreadm was
a remnant from something Berkeley never got around to doing.  It
relates to "pg_fod" (Fill-on-demand) and "pg_fileno" in "struct fpte".
My guess is pg_vreadm has something to do with being able to
pagein text/data from files other than the file that was exec-ed
(maybe part of a shared-memory scheme or something)???
I have no idea what pg_swapm was intended for.  Anyone know for
sure what the origin and/or use of these fields are?  We are porting
the virtual-memory code to a 68020, and I don't want to eliminate them
if 4.3BSD (or whatever they plan to call it) makes use of them.  Thanks!

	-Dan Chernikoff
	Cadlinc, Inc
	Arpanet: dan@sri-tsc
	Usenet: {decwrl,hplabs}!turtlevax!danc