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From: pha@zippy.eecs.umich.edu (Paul Anderson)
Newsgroups: comp.sys.amiga.tech
Subject: Re: IRQ virus (and a personal note to Steve)
Message-ID: <1387@zippy.eecs.umich.edu>
Date: 5 Jan 89 19:31:54 GMT
References: <10788@s.ms.uky.edu> <1410014@hpcvca.HP.COM>
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Reply-To: pha@zippy.eecs.umich.edu (Paul Anderson)
Organization: University of Michigan EECS Dept. Ann Arbor
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In article <1410014@hpcvca.HP.COM> charles@hpcvca.HP.COM (Charles Brown) writes:
>
>So Amiga could be modified to use VM and even demand paging and still
>have provisions for real time.
>
>I expect to get flamed for this.  There are several people who read
>this notes group who are violently opposed to demand paging for
>performance reasons.  However, they simply do not know what they are
>talking about.  Its really very simple.  There are two cases:
>  1.  All processes will fit into physical RAM.
>     Not demand paged:  Runs fast.
>     Demand paged:  No paging.  Runs just as fast.
>  2.  Processes will NOT fit into physical RAM.
>     Not demand paged:  WILL NOT RUN.  Either fails to load or crashes.
>     Demand paged:  Pages.  Runs slow, but at least it still runs.
>--
>	Charles Brown		charles%hpcvca@hplabs.hp.com
>	Not representing my employer.

Probably the right way to handle this is give processes the ability to wire
down pages they want locked in physical RAM.  A simple system call will let
time critical application wire their interrupt handling code, buffers, and whatnot, but
still let the rest of the application be paged if it isn't performance critical.

I don't think you should get flamed for wanting paging, since it is generally
a good thing, especially when solving real time problems isn't that agonizing.

Along the lines of this discussion, is anyone doing a 4.3 or Mach port to
the Amiga?  I know someone is doing a Mac-II port, and I am working on
a Mach port to the Apollo.  The only reason I ask is that if this isn't
being done, maybe it should be, cause the Amiga hardware is kinda nice (mostly
cheep, I guess).  I know about the 2500 unix box, but I'm not that thrilled
by system V.

Paul Anderson
CAEN Apollo Systems Programmer
UofMich