Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!agate!violet.berkeley.edu!edmoy
From: edmoy@violet.berkeley.edu (;;;;YF37)
Newsgroups: comp.sys.mac
Subject: Re: LightSpeed C gripes
Message-ID: <6662@agate.BERKELEY.EDU>
Date: 22 Jan 88 19:32:50 GMT
References: <4Vw6hny00WAK5w00JJ@andrew.cmu.edu> <1072@cpocd2.UUCP>
Sender: usenet@agate.BERKELEY.EDU
Reply-To: edmoy@violet.berkeley.edu.UUCP ()
Organization: University of California, Berkeley
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In article <1072@cpocd2.UUCP> howard@cpocd2.UUCP (Howard A. Landman) writes:
>I have a fairly simple UNIX application that I was hoping to port to the Mac.
>Unfortunately, the system architecture is such that the program's database is
>kept in (virtual) memory, in a couple of 2 MB arrays (will need to increase size
>soon, as that is almost all used).  Under a true VM system like UNIX, the
>program has a working set of about 160 KB - most of the database is not needed
>at any given instant, so it is automatically paged out to disk.  I can easily
>run the program on a machine with only 1 MB RAM, even though the program
>virtual image is about 4.5 MB (and growing), and the UNIX kernel (which is
>locked in core) eats up over 250 KB.
>
>Am I wrong in stating that this program simply cannot be made to run in 1 MB
>on a Mac without major recoding?  I like my Mac, but (because of stuff like
>this) don't plan to program on it until AUX is available on a system I can
>afford.

The only way to do this is to implement your own "virtual memory".  I remember
having to maintain a program on a 4BSD VAX Unix system (has 32 bit virtual
memory) and on a version 7 unix system on a PDP (has only 16 bit virtual
memory).  I have #ifdef's in many places, depending on whether I could index
into the array directly (on the VAX) or whether I had to read a piece of the
array from a disk file before indexing (on the PDP).  Fun, fun, fun :-)

Edward Moy
Workstation Software Support Group
University of California
Berkeley, CA  94720

edmoy@violet.Berkeley.EDU
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