Path: utzoo!utgpu!water!watmath!watcgl!watsol!bmacintyre
From: bmacintyre@watsol.waterloo.edu (Blair MacIntyre)
Newsgroups: comp.sys.amiga
Subject: Re: AmigaDos don't thrash no more!
Message-ID: <3247@watcgl.waterloo.edu>
Date: 15 Feb 88 18:10:16 GMT
References: <8504@sunybcs.UUCP>
Sender: daemon@watcgl.waterloo.edu
Reply-To: bmacintyre@watsol.waterloo.edu (Blair MacIntyre)
Organization: U. of Waterloo, Ontario
Lines: 30

In article <8504@sunybcs.UUCP> ugpete@sunybcs.UUCP (Peter Theobald) writes:
><Line Eater Motel. Line eaters check in.... but they don't check out!>
>
>AmigaDos should sort disk requests by track. This way if three processes
>ask for three different files scattered all over the disk, instead of
>jumping around like a Tasmianian Devil getting blocks from first one
>file, then the other then back to the first, AmigaDos would load in the
>blocks on the tracks currently nearest the read head. Then it would move
>the head to the next track with requested data on it, etc... It could
>continue this process sweeping the head back and forth across the disk
>picking up what is needed, wasting the least amount of time.
>	This would eliminate thrashing, and would speed up disk accesses
>to boot! I think this is similar to what a clone of Peter da Silva meant by
>single-threading loadSegs.
>	How major a change in AmigaDog is this?

Unfortunately, this scheme could cause starvation ( ie. a certain read 
request doesn't get serviced because it's on the opposite end of the
disk ) not to mention problems with syncronizing reads and writes if you
start using a selection order other than first-come-first-serve.

Nice thought, though.
:-)

Blair
--
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Blair MacIntyre (bmacintyre@watsol.waterloo.edu) ( Long live the Amiga!! )///
University of Waterloo, Center for the New Oxford English Dictionary  \\\///
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