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From: suitti@pur-phy.UUCP (Stephen K. Uitti)
Newsgroups: net.unix-wizards
Subject: Re: scheduling/timing weirdo
Message-ID: <1331@pur-phy.UUCP>
Date: Mon, 14-May-84 17:33:37 EDT
Article-I.D.: pur-phy.1331
Posted: Mon May 14 17:33:37 1984
Date-Received: Thu, 17-May-84 03:06:44 EDT
References: <4170@ukc.UUCP>
Organization: Purdue University Physics Dept.
Lines: 19


	You added some optimal code to a PDP 11/45 program and it
slowed down in system time.
	One of the things that can happen to a machine with a small
address space is that you can run out of data space.  In this case,
it may be that stdio can't malloc more space for a new buffer.  If
this happens, it silently doesn't bother buffering.  You get single
character writes, that is, one sys call per character.  Sometimes
this will increase your user time two.
	This shouldn't happen if you compile with split instruction
& data (which, if memory serves, is available on an 11/45).  We have this
kind of problem from time to time with "vnews" on our 11/44.  The only
other thing I can think of is that you do more swapping with a
bigger processes (not a problem on 11's with > 1 Meg of RAM).  This is
unlikely for a small change.

Stephen Uitti (Purdue physics site manager)
UUCP:		pur-ee!Physics:suitti, purdue!Physics:suitti
INTERNET:	suitti @ pur-phy.UUCP