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From: torrie@cs.stanford.edu (Evan J Torrie)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: How do we change the scheduler? (Was Re: Multitasking at home...)
Message-ID: <1991Jan27.214435.15976@Neon.Stanford.EDU>
Date: 27 Jan 91 21:44:35 GMT
References: <1991Jan18.231330.16290@Neon.Stanford.EDU> <7553@sugar.hackercorp.com>     <1991Jan21.004720.25985@ncsuvx.ncsu.edu> <12880@life.ai.mit.edu>     <1991Jan21.072642.23587@Neon.Stanford.EDU> <10620.tnews@templar.actrix.gen.nz>  <1991Jan22.215801.4557@Neon.Sta
Sender: torrie@Neon.Stanford.EDU (Evan James Torrie)
Organization: Computer Science Department, Stanford University
Lines: 49

jbickers@templar.actrix.gen.nz (John Bickers) writes:

>Quoted from <1991Jan23.213736.28220@Neon.Stanford.EDU> by torrie@cs.stanford.edu (Evan J Torrie):
>> jbickers@templar.actrix.gen.nz (John Bickers) writes:

>>   How does a program become an input handler?  I presume you can spawn
>> off a task, and tell it to be an input handler...   

>[lots of good explanations deleted]
>    constructs a message, and then executes this list of handlers. So
>    your code will be executed as part of the input.device task. This
>    means the programmer needs to pay attention to what stack and local
>    variables their handler expects to be using. Not hard.

  Just as a matter of interest, it seems to me that this design would
be somewhat difficult to graft virtual memory/memory protection onto
without some serious backward compatibility problems...  
  Has anyone thought about adding VM/protection onto AmigaDos??  Is it
going to be a problem?  


>>   I'm just wondering if you would get better response by having the OS
>> temporarily boosting the priority of an interactive task (e.g. raising

>    I don't believe there is a good OS solution. A user may not want
>    a download halted while their word-processor scrolls its display
>    a bit faster.

>    Or whatever. The interactions involved between Intuition and all the
>    tasks involved seem too complicated to me for an OS solution to be
>    practical. A user can send time-consuming events to a number of
>    tasks at the same time, for example. No, I'd leave this for the user
>    to decide with something like Xoper, and only make broad assumptions
>    at the application design level.

  Perhaps that may be best.  My question was whether there have been
any studies done in this area.  If you read all the classic OS design
textbooks, they're all written around the assumption of large
timesharing multiuser OSes... none that I've seen give much thought to
a single user multitasking OS.
  For example, I believe the Amiga OS was derived from Tripos? by
Metacomco?.  What was the original design decision behind the Amiga OS
ancestors?

-- 
------------------------------------------------------------------------------
Evan Torrie.  Stanford University, Class of 199?       torrie@cs.stanford.edu   
"If it weren't for your gumboots, where would you be?   You'd be in the
hospital, or in-firm-ary..."  F. Dagg