Path: utzoo!attcan!uunet!mcsun!ukc!edcastle!aiai!richard
From: richard@aiai.ed.ac.uk (Richard Tobin)
Newsgroups: comp.arch
Subject: Re: Single user vs. shared
Message-ID: <2201@skye.ed.ac.uk>
Date: 11 Apr 90 13:36:50 GMT
References: <1712@aber-cs.UUCP> <1990Apr10.225542.13662@world.std.com>
Reply-To: richard@aiai.UUCP (Richard Tobin)
Organization: AIAI, University of Edinburgh, Scotland
Lines: 26

In article <1990Apr10.225542.13662@world.std.com> bzs@world.std.com (Barry Shein) writes:
>I thought compiling hasn't been disk intensive for years, it's CPU
>intensive. Does anyone have measurements? 

That depends what you're compiling.  If your compiling hundreds of small
programs on a Unix system with fairy little real memory, most of the time
will be spent paging cpp, ccom, c2 and ld (or equivalent).

I recently built a system which generated about a thousand C files of
about 100 lines each, then compiled them.  During compilation on a
fairly lightly-loaded multi-user Sun with 8 Mb (which took *hours*)
user cpu usage was less than 10% on average.

It's easy to produce the opposite behaviour too.  I have a C function
(the interpreter for a virtual machine) which is 2000 lines long
(including comments).  It takes about 45 minutes to compile with -O4 on
a Sun 4/260 with 32Mb.  This is almost all user cpu time.

(Aside: it takes 10 seconds to compile with gcc, which produces code
that is only 10% slower and has the advantage of being correct.)

-- Richard
-- 
Richard Tobin,                       JANET: R.Tobin@uk.ac.ed             
AI Applications Institute,           ARPA:  R.Tobin%uk.ac.ed@nsfnet-relay.ac.uk
Edinburgh University.                UUCP:  ...!ukc!ed.ac.uk!R.Tobin