Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83 (MC840302); site boring.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!mhuxn!mhuxr!ulysses!allegra!mit-eddie!think!harvard!seismo!mcvax!boring!jack
From: jack@boring.UUCP
Newsgroups: net.sources.bugs,net.unix-wizards
Subject: Funny behaviour of bm under V7
Message-ID: <6591@boring.UUCP>
Date: Wed, 21-Aug-85 15:37:47 EDT
Article-I.D.: boring.6591
Posted: Wed Aug 21 15:37:47 1985
Date-Received: Sat, 24-Aug-85 17:15:22 EDT
Reply-To: jack@mcvax.UUCP (Jack Jansen)
Organization: AMOEBA project, CWI, Amsterdam
Lines: 43
Xref: watmath net.sources.bugs:454 net.unix-wizards:14497
Apparently-To: rnews@mcvax.LOCAL


I'm posting this to unix-wizards too, since I can't pin the
problem on 'bm', so there might be something funny going on
in the V7 kernel.

I observed some very weird behaviour of the Boyer Moore program
posted to net.sources recently.
The problem is: user time is significantly less than that of grep,
but system time is preposterous. Times are as follows, on an 11/34,
running more-or-less v7m, 1Mb, Ampex Capricorn:

---
+ time bm Zurich /usr/dict/words 
Zurich

real     1:00.0
user        3.5
sys        42.7
+ time fgrep Zurich /usr/dict/words 
Zurich

real       33.0
user       18.5
sys         6.6
+ time grep Zurich /usr/dict/words 
Zurich

real       22.0
user       11.2
sys         6.4
---
I tried fiddling with the buffer size being read (512,1024,2048),
but timing stays the same.
Also, profiling shows that the program spends 90% of the time in
read(), so there are no other system calls that could account for
the time difference.
So, what is going on that's making bm 8 times slower than everyone
else?

Anyone out there who can give me a hint on where to look?
-- 
	Jack Jansen, jack@mcvax.UUCP
	The shell is my oyster.