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From: hamilton@uxc.cso.uiuc.edu
Newsgroups: comp.sys.amiga
Subject: Re: New Exec calls needed: (was Re: Tra
Message-ID: <172200056@uxc.cso.uiuc.edu>
Date: Sun, 24-May-87 14:37:00 EDT
Article-I.D.: uxc.172200056
Posted: Sun May 24 14:37:00 1987
Date-Received: Tue, 26-May-87 01:39:28 EDT
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Nf-ID: #R:<8705222220.AA29170@cory.Berkele:-38:uxc.cso.uiuc.edu:172200056:000:1817
Nf-From: uxc.cso.uiuc.edu!hamilton    May 24 13:37:00 1987


dillon@CORY.BERKELEY.EDU says:
> 	What is needed is another couple of Exec calls allowing one to
> install a "memory low" signal to task X (allowing any number of tasks to do
> this).  You would specify some sort of low-water mark below which you
> want to be notified that memory is running low, and a high-water mark
> above which you want to be notified that there is plenty of memory.  The marks
> should be placed far enough away so that you don't get into any infinite 
> oscillation loops (could occur when several tasks are using the feature).
>	Then, Exec would signal the specified tasks (with either the high
> water or low water signal) when the specified condition occurs.

    nice idea, but it doesn't require "another couple of Exec calls"
(beware creeping featurism).  simply create a background task with a
"well-known" port name, send "add-me-to-your-distribution-list" and
"drop-me..." messages to it from your application, and monitor your
own port for status bulletins.
    you could take it further, creating a "memory broker".  some
applications need large quantities of RAM on an all-or-nothing basis
(bitmaps, waveforms, etc), while others can take it or leave it
(huge stdio buffers, auxiliary track buffers, etc).  the broker
would allow the first class of application to request that the second
class relinquish some resources.  sorta like what sometimes happens
on overbooked airline flights - asking for volunteers to fly later.
we already have a simple form of this: the Expunge entry of libraries
and devices.

	wayne hamilton
	U of Il and US Army Corps of Engineers CERL
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