Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!mips!hal!mark
From: mark@mips.COM (Mark G. Johnson)
Newsgroups: comp.benchmarks
Subject: Re: A short io benchmark...
Keywords: linearity
Message-ID: <43942@mips.mips.COM>
Date: 10 Dec 90 21:14:16 GMT
References: <9456@ncar.ucar.edu>
Sender: news@mips.COM
Reply-To: mark@mips.COM (Mark G. Johnson)
Lines: 31

In article <9456@ncar.ucar.edu>, pack@acd.ucar.edu (Dan Packman)
gives a short benchmark program that exercises I/O.  He presents
measured data for n simultaneous processes reading the same file,
and also data for k processes simultaneously reading different
files.  Dan writes:
    >The first test shows remarkable linearity through 7
    >simultaneous processes.

I repeated Dan's test of simultaneous processes reading the same
file (using Dan's pgm to create that specific file) and found a modest
degree of better-than-linearity (slope a bit less than one).

Measurements on the two workstations
    >in elapsed seconds on an otherwise unloaded machine:

                             # of simultaneous processes reading same file
 Hardware                     1      2      3      4      5      6      7
----------------------------------------------------------------------------
IBM RS6000/320       [dan]   16.5   31     47     64     80    101    119
MIPS RS3230 Magnum   [mgj]   11.3   21.1   31.0   40.9   50.7   60.8   71.0

The (slight) difference between the two machines is the incremental cost
of the 2nd process.  For the IBM, each process costs about 16.5 seconds.
For the Magnum, each process costs around 9.9 seconds, *except* the first
one which costs 11.3.  Also the IBM begins to depart from linearity
at n>5 processes, when the cost per process rises again.  At least thru
7 processes the Magnum seems not to do this.
-- 
 -- Mark Johnson	
 	MIPS Computer Systems, 930 E. Arques M/S 2-02, Sunnyvale, CA 94086
	(408) 524-8308    mark@mips.com  {or ...!decwrl!mips!mark}