Path: utzoo!mnetor!uunet!husc6!hao!boulder!sunybcs!ugpete
From: ugpete@sunybcs (Peter Theobald)
Newsgroups: comp.sys.amiga
Subject: Re: AmigaDos don't thrash no more!
Message-ID: <8626@sunybcs.UUCP>
Date: 18 Feb 88 04:35:24 GMT
References: <8504@sunybcs.UUCP> <3247@watcgl.waterloo.edu>
Sender: nobody@sunybcs.UUCP
Reply-To: ugpete@joey.UUCP (Peter Theobald)
Organization: SUNY/Buffalo Computer Science
Lines: 31

< This sure looks like line-eater food to me! >


In article <3247@watcgl.waterloo.edu> bmacintyre@watsol.waterloo.edu (Blair MacIntyre) writes:
>In article <8504@sunybcs.UUCP> ugpete@sunybcs.UUCP (Peter Theobald) writes:
>>
>>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.

>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.

>Blair

No, that wouldn't cause starvation. The disk would service every request on
cylinders 0 - 79 in that order, and then service every request on tracks
79 - 0 in that order (or however # of cylinders there are). This process
would repeat until there are no more requests. A request cannot be starved
because it must at most wait for the head to travel to one extreme and back.

	-Pete

Peter Theobald				SUNY/Buffalo Computer Science
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