Title :
On Input/Output Speedup in Tightly Coupled Multiprocessors
Author :
Abu-Sufah, Walid ; Husmann, Harlan E. ; Kuck, David J
Author_Institution :
Center for Supercomputer Research and Development, University of Illinois, Urbana, IL 61801.
fDate :
6/1/1986 12:00:00 AM
Abstract :
Previous models of program speedup on parallel architectures tend to ignore I/O activity and other important issues. In this paper we derive analytic speedup models including I/O activities. We show that ignoring I/O yields conservative speedup results. We explore the effectiveness of using hardware format conversion units in multiprocessors [33]. We prove that hardware parallel format conversion loses its edge over software parallel format conversion if the ratio of the number of processors to I/O bandwidth increases. For a given number of processors, program speedup is more sensitive to the available I/O bandwidth rather than the format conversion speed. Ninety-one Fortran programs are used in various experiments to verify our models and conclusions. Most of the programs are I/O bound. Our empirical results show that including I/O activity improves the speedup factor for 78 percent of the programs, and 18 percent of the programs are sped up only due to faster I/O activities. For a serial machine, using hardware format conversion units designed in [13] reduces program execution time by an average factor of three. The software format conversion speed used is obtained from direct measurements on an IBM 4341 running CMS and a CDC Cyber 175 running NOS. For multiprocessor systems a factor of eight increase in the processors to I/O bandwidth ratio reduces the effectiveness of hardware format conversion to an average factor of 1.36.
Keywords :
Bandwidth; Concurrent computing; Hardware; Memory architecture; Power measurement; Solid state circuits; Supercomputers; Systolic arrays; Velocity measurement; Very large scale integration; Format conversion time; I/O bandwidth; multi-processor; processor to I/O bandwidth ratio; program speedup models;
Journal_Title :
Computers, IEEE Transactions on
DOI :
10.1109/TC.1986.5009429