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From: cs450a03@uc780.umd.edu
Newsgroups: comp.protocols.nfs,comp.arch
Subject: RE:  Offloading I/O [was:Incremental sync()s ...]
Message-ID: <18MAR91.09033243@uc780.umd.edu>
Date: 18 Mar 91 09:03:32 GMT
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For the case of an IOP....

line-orientation is an approximation of what you want, but not exactly.  

Essentially, what you need is a way of saying "just stuff these
characters in the buffer, but when you get one of those characters,
send the buffer up to me for handling."   'Implicitly', if the buffer
gets nearfull, you'll have to read it anyways.

Information of this sort could be communicated by sending short lists
of characters (turn on pass through for these, turn off pass through
for these), sending blanket commands (turn off pass through for all),
or sending bitmaps (set passthrough as indicated, for all characters).

As always, when you introduce a new class of feature, there will be
lots of programs that cannot take advantage of the feature.  Most
notably, programs where you have no source code access (nor a support
contract).

On the other hand, this mechanism is pretty general, and could be
implemented with a few kernal mods (in the case of unix), and a little
out-board hardwre.

Note that mostly I'm thinking about buffering printing characters, and
sending control characters (including delete) through to the 'main
processor' .. so perhaps you could get away with a simple switch to
turn on/turn off such a feature.

How useful?  How many users?  What is communication overhead?

I think this would integrate pretty well with something like emacs..
though it is arguable how much cpu overhead you'd "save" in that case.

Which, I suppose, is the reasoning behind X-terminals.

Raul Rockwell