From: utzoo!decvax!genrad!mit-eddi!smh
Newsgroups: net.unix-wizards
Title: Re: Why overlap I/O and processing?  clutches...
Article-I.D.: mit-eddi.129
Posted: Thu Apr 21 20:54:13 1983
Received: Fri Apr 22 04:18:20 1983
References: ittvax.694

Enough talk about the possible benefits of aynchronous IO with
tapes, pipes, etc.  Did it occur to anyone that some aspects of
the question can be trivially tested.  On an unloaded system:
	tar cvfb /dev/rmt0 20 LOTSA.FILES
and:
	tar cvf - LOTSA.FILES | dd ibs=1b obs=20b of=/dev/rmt0
where LOTSA.FILES is some substantial directory tree.  A simple
timing would tell a lot.  I am willing to try this with an 11/45
and TU10 (800BPI 45IPS) if someone else would volunteer to try
it on hardware at the other end of the spectrum, i.e., a 780
with a TU78.  Of course, the 11 will certainly suffer from
contention for scarce kernel IO buffers for the pipe and all the
tar file reading.  Perhaps a blocking factor of 10 could be tried
as well.

I will post results when I get them.
					Steve Haflich
					genrad!mit-eddie!smh