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From: torrie@cs.stanford.edu (Evan J Torrie)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Single user OS schedulers (Was Re: How do we change the scheduler?)
Message-ID: <1991Jan27.221224.17360@Neon.Stanford.EDU>
Date: 27 Jan 91 22:12:24 GMT
References: <1991Jan25.073516.29644@Neon.Stanford.EDU> <1991Jan26.035750.11786@NCoast.ORG> <1991Jan27.014242.2863@Neon.Stanford.EDU> <1991Jan27.070050.220@news.iastate.edu>
Sender: torrie@Neon.Stanford.EDU (Evan James Torrie)
Organization: Computer Science Department, Stanford University
Lines: 44

skank@iastate.edu (Skank George L) writes:

>In article <1991Jan27.014242.2863@Neon.Stanford.EDU> torrie@cs.stanford.edu (Evan J Torrie) writes:
>>  Even if I run a raytracer at priority -1, and then another compute
>>bound task, (say calculating Pi at priority 0), then the raytracer
>>will starve...  To a person coming from a Unix background, this is not
>>attractive (in fact, one might be tempted to not even call it "true"
>>multitasking [ducking for cover :-)]).

>     With all due respect the above is a rather silly example.  First, I doubt
>that you are actually running a ray tracer in the foreground, therefore, if it
>is starving you won't notice (same as on Unix so far).  

  Ah, why won't I notice it starving if it is running in the
background?  It's sitting there in a background window, doing nothing
at all on the Amiga, whereas under Unix, the XWindows display is
getting updated, albeit slowly, while the Pi generator is still
running (at a faster rate).

>The fact that you set
>the priority of the ray-tracer to -1 and the priority of the program
>calculating Pi at 10 says to me that you wanted the program calculating Pi to
>a *lot* have more CPU time (same as Unix).

  On the Amiga, though, this absolute difference in priority makes no
difference (does that make sense? :?)  Even if I set the difference in
priorities to be just 1, the ray tracer will still get ZERO time
slices and the PI calculator gets everything.  Under Unix, the
proportion of timeslices shared between two tasks is proportional to
the absolute difference in priorities.
  
>     Finally, AmigaDOS is not UNIX (and I think too many Amiga owners forget
>this also).  Comparing AmigaDOS and Exec to Unix and it's exec is fine but
>don't expect them to be the same because they are not.  

  A good point.  From what I've read so far, it seems that the Amiga
scheduler is a better than Unix for a single user system.  But I
wonder whether it could be made even better...

-- 
------------------------------------------------------------------------------
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