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From: darrell@sdcsvax.UUCP
Newsgroups: comp.os.research
Subject: Re: UNIX Facilities for Interpreters
Message-ID: <3326@sdcsvax.UCSD.EDU>
Date: Sat, 13-Jun-87 02:05:01 EDT
Article-I.D.: sdcsvax.3326
Posted: Sat Jun 13 02:05:01 1987
Date-Received: Thu, 18-Jun-87 03:36:52 EDT
Organization: AT&T Bell Laboratories, Holmdel
Lines: 39
Approved: mod-os@sdcsvax.uucp


In article <3293@sdcsvax.UCSD.EDU>, boba@iscuva.ISCS.COM (Bob Alexander) writes:
+> Modern, memory managed operating systems (like UNIX) have addressed
+> quite nicely certain special requirements of executable files.  In
+> particular (1) the file (text and data) need not be loaded into memory
+> in its entirety to begin executing, and (2) the pages can be shared
+> among processes that are executing them (both on disk and in memory).
+> 
				:
+> 
+> For interpreters to take full advantage of this facility, they would
+> have to interpret their p-code "as is" as it sits on disk.  If they
+> modify the code, much of the advantage would be lost.
+> 
+> I'd be interested in hearing your comments and suggestions regarding
+> this idea; alternative ideas to solve this problem, ways other OSs have
+> dealt with it, implementation problems, or gross oversights.  What
+> would you think of a "read only" option for this function (a fourth
+> argument?), where the data would be mapped as read only (i.e.
+> protected).
+> -- 
+> 
more recent versions of system v have improved support for interpreters.
for one, there is a new region type called "doubly mapped memory".  a
single region can be treated as both text and data (exactly what interpreters
do with their p-code).  add that with the copy on write feature of
the demand paging system and you have most of the advantages that you
desire.

danny chen
ihnp4!homxc!dwc



-- 
Darrell Long
Department of Computer Science & Engineering, UC San Diego, La Jolla CA 92093
ARPA: Darrell@Beowulf.UCSD.EDU  UUCP: darrell@sdcsvax.uucp
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