Path: utzoo!utgpu!water!watmath!clyde!rutgers!cmcl2!nrl-cmf!ames!pasteur!ucbvax!USU.BITNET!FATQW
From: FATQW@USU.BITNET
Newsgroups: comp.sys.amiga
Subject: Re: Disk thrashing
Message-ID: <8802210532.AA14542@jade.berkeley.edu>
Date: 21 Feb 88 04:27:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 23

>...A request cannot be starved
>because it must at most wat for the head to traver to one extreme and back.
                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
And why should it do this?  The trackdisk
   device should have an internal
flag stating the current direction of head movement.  After it finishes a
request, it looks in the direction specified by the flag and goes to the
next request in that direction.  If there aren't anymore requests in that
direction, it does an about-face and starts going the other direction.

If this was put in the trackdisk device, I think that something should be
done in LoadSeg(), Read(), and Write().  For a long Read() or Write(),
it should submit as many requests as possible to the trackdisk device at
the same time, so the trackdisk device could optimize it.  Just make
sure LoadSeg() operates on big Read()s rather than lots of small ones.
(I think this is already the case, but I'm not sure.)

                                Bryan

        Bryan Ford                    //// A computer does what \\\\
Snail:  1790 East 1400 North         //// you tell it to do, not \\\\
        Logan, UT 84321         \\\XX///  what you want it to do. \\\XX///
Email:  FATQW@USU.BITNET         \XXXX/ Murphy's Law Calendar 1986 \XXXX/