Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!columbia!cheshire.columbia.edu!yoram
From: yoram@cheshire.columbia.edu (Yoram Eisenstadter)
Newsgroups: comp.arch
Subject: Re: Kernel build times, esp. on Amdahl
Message-ID: <4794@columbia.UUCP>
Date: Tue, 7-Jul-87 22:22:39 EDT
Article-I.D.: columbia.4794
Posted: Tue Jul  7 22:22:39 1987
Date-Received: Fri, 10-Jul-87 07:20:52 EDT
References: <502@winchester.UUCP>
Sender: nobody@columbia.UUCP
Reply-To: yoram@cheshire.columbia.edu (Yoram Eisenstadter)
Followup-To: comp.arch
Distribution: na
Organization: Columbia University CS Department
Lines: 44
Keywords: benchmarks
Summary: Amdahl's numbers seem quite reasonable.

In article <502@winchester.UUCP> mash@mips.UUCP (John Mashey) writes:
>I've been intrigued by Amdahl's recent recruiting ads that say they
>build a UNIX kernel in 3 minutes.  Can anybody from Amdahl say:
>1) what model this is on?
>2) is 3 minutes CPU time, or real time, and what's the other number?
>3) is this optimized or unoptimized?
>
>For comparison:
>UNIX kernel make from scratch times: 4.3BSD+NFS, MIPS M/1000:
>239.7u 74.5s 12:39 41% 99+231k 6739+6986io 3167pf	unoptimized
>492.6u 100.3s 18:53 52% 174+313k 8591+8880io 3901pf 	optimized -O2

I'm not from Amdahl, but here goes anyway...

Since C compiles do a great deal of I/O (reading in source and .h
files, writing out temp files, reading in temp files, writing out
object files) it seems to me that any benchmark of a kernel-make
would be heavily dependent on the kind of disk drives attached to
the processor.

If Amdahl's figures come from a system that's similar to current
large IBM mainframes (I don't know much about Amdahl's products,
except that they're 370-architecture compatible), they would
typically have fast disk drives with large, expensive controllers
hooked up via fast block-multiplexor channels.  I doubt that MIPS
boxes come with such I/O devices.  (Amdahl may even have CPUs which
are faster than MIPS's; who knows?  :-) )

By the way, note that John's benchmarks show that the CPU is idle
about half the time, probably waiting for disk reads to complete.

Also, assuming Amdahl's numbers represent wall-clock time (and
their kernel is as big as 4.3BSD+NFS), they are only 4 to 6 times
faster than John's numbers.  The fact that the largest
conventional mainframe is 4 to 6 times faster than a small RISC
processor (is the MIPS a single-chip CPU? single board?) doesn't
really surprise me very much.

Cheers..Yoram

Yoram Eisenstadter                     | Arpanet: yoram@cs.columbia.edu
Columbia University                    | Usenet:  seismo!columbia!cs!yoram
Dept. of Computer Science              | Bitnet:  yoram%cs.columbia.edu@WISCVM
New York, NY 10027                     | Phone:   (212) 280-8180