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From: eeh@public.BTR.COM (Eduardo E. Horvath  eeh@btr.com)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: How do we change the scheduler? (Was Re: Multitasking at home...)
Message-ID: <1497@public.BTR.COM>
Date: 29 Jan 91 04:54:58 GMT
References: <1991Jan18.231330.16290@Neon.Stanford.EDU> <7553@sugar.hackercorp.com> <1991Jan23.213736.28220@Neon.Stanford.EDU> <7609@sugar.hackercorp.com> <1991Jan27.005727.1196@Neon.Stanford.EDU>
Organization: BTR Public Access UNIX, MtnView CA, Contact: cs@btr.com 415-966-1429
Lines: 47

In article <1991Jan27.005727.1196@Neon.Stanford.EDU> torrie@cs.stanford.edu (Evan J Torrie) writes:
>peter@sugar.hackercorp.com (Peter da Silva) writes:
>
>>In article <1991Jan23.213736.28220@Neon.Stanford.EDU>, torrie@cs.stanford.edu (Evan J Torrie) writes:
>>> priority).  But normally, the code to regenerate the window's view
>>> (what I call an Update event) is located in the main word processor
>>> task.

>>A word processor would probably not be split up this way, because they don't
>>tend to be compute bound. This would be more like a spreadsheet.

>>Also, the display would be handled by the user-interface task. The compute
>>task just updates internal tables... the display selects the portions of those
>>tables the user wants to see and presents them.

>  So the two tasks share the same address space/structures etc??  Do
>the commercially available programs on the Amiga actually DO this?
>(e.g. the WordPerfect, Advantage, or whatever the WPs, SSs and DBs
>are...)


	Yes, as a matter of fact WordPerfect does spawn several tasks.  There
is WordPerfect itself, the printer process, and the spell-checker/thesaurus.
These are completely separate programs, and can be invoked separately.  I often
print out documents while editing text and percieve no slowdown in the interface
at all.  As a matter of fact, WordPerfect spawns a new task for each document
that is being editted (a fact that wasn't easy to find because these tasks are
called "kashmir".  Wonder why.)  I suppose that this means two users could 
both be running WordPerfect on the same machine concurrently, if the input
re-direction problem could be solved.

	On the Amiga, all tasks share the same address space.  Structure
sharing is a more complicated question.  In general, shared memory is not
a good solution to the problem of inter-process communication because it
makes programs unreasonably complicated.  It becomes impossible to keep
track of which task modified a location last, and makes debugging next
to impossible.  What's more important is that the tasks are sharing the
same code.  WP is implemented with a heavy reliance on dynamic libraries
and lightweight threads, so several instances of WP editing different
documents take up very little room.


-- 
=========================================================================
Eduardo Horvath				eeh@btr.com
					..!{decwrl,mips,fernwood}!btr!eeh
	"Trust me, I am cognizant of what I am doing." - Hammeroid