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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.micro.68k
Subject: Re: Re: Holy Holistic, Batman!  (OS-9 and the art of being holistic)
Message-ID: <6172@utzoo.UUCP>
Date: Mon, 25-Nov-85 17:42:46 EST
Article-I.D.: utzoo.6172
Posted: Mon Nov 25 17:42:46 1985
Date-Received: Mon, 25-Nov-85 17:42:46 EST
References: <576@sftig.UUCP> <1001@bnl44.UUCP> <11467@rochester.UUCP>
Organization: U of Toronto Zoology
Lines: 30

> And easy to change one of those beasts?  If device descriptors are to live in
> ROM, there must be a way of updating them unless you are resigned to a static
> system.

If you put it in ROM, you can't change it; that's the way the technology
works, guys.  But it's fine for stuff you don't want to change.

> Also, can they be handled from ROM, RAM or disk simultaneously?

I'm not quite sure what you mean.  Certainly the system on which I am writing
this has one of its filesystems in RAM and the rest on disk.  There would be
no great problem writing a driver that mixed media within one filesystem,
since nothing but the driver *cares* how the bits are stored, although
using the combination effectively could get complicated.

> Or have you had as much hacking on the pipes as you can stand?  I don't see
> any reason pipe access should be tied to the filesystem in any manner other
> than the "common access method".  To access the file systems only slows
> things down...

There are people who have implemented Unix pipes completely independently of
the file system.  We simply didn't think it was worth the effort.  Our time
is valuable; we didn't think there was enough further performance improvement
to be had (given that things like system-call overhead, data copying, etc.
are invariant) to be worth it.  It's probably worth it if you're starting
from scratch, but the overhead of going through the filesystem code is a
performance nuisance rather than a performance disaster.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry