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A Model of Concurrent Tasks Within Jobs of a Multiprogramming System

IP.com Disclosure Number: IPCOM000128510D
Original Publication Date: 1974-Dec-31
Included in the Prior Art Database: 2005-Sep-16
Document File: 17 page(s) / 49K

Publishing Venue

Software Patent Institute

Related People

M. Maekawa: AUTHOR [+4]

Abstract

A technique often used to study performance patterns in computer systems is to model the behavior of programs in execution on these systems. Programs in execution may be modeled as a collection of tasks requiring the use of system resources for their execution: Among others these resources include the central processing units, CPU, and the input/output processors, I/0. The corresponding tasks are called CPU and I/0 tasks. The algorithms for allocating these resources to competing tasks are factors in determining the performance of the system. If the systems under consideration are batch-?processing systems, the performance criterion is usually job throughput rate. Tdotable analyses of these systems have been performed by Gaver [7], Easkett [2], and Boyd [3]. An underlying assumption of the models used in these studies is that the CPU tasks and 1/0 tasks of an individual job aye executed sequentially;.that ls, for a given job in the system model, "no provision is made to allow concurrency of CPU tasks and I/0 tasks. The purpose of this study 3.s to construct a model which allm?s this type of concurrency, then to investigate its effects on job throughput rate under various algorithms of resource allocation.l The basic job and system models are defined. in the following section. Also in that section,- two important parameters Nilaich relate to the load of the system and the con-currency of tasks within a job. are defined and discussed: In section III, three system models vahich include nonpreemptive and preemptive CPU schedules axe outlined. Finally in section IV, numerical results axe presented along; ~,Yith observations based on these results.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

A Model of Concurrent Tasks Within Jobs of a Multiprogramming System

by M. Maekawa and D.L. Boyd

Computer, Information, and Control. Sciences

Institute of Technology

University of Minnesota

r13.nneapolis, ?w.nnesota 55455

Technical Penort 74-1

January, 1974

1. Introduction

A technique often used to study performance patterns in computer systems is to model the behavior of programs in execution on these systems. Programs in execution may be modeled as a collection of tasks requiring the use of system resources for their execution: Among others these resources include the central processing units, CPU, and the input/output processors, I/0. The corresponding tasks are called CPU and I/0 tasks. The algorithms for allocating these resources to competing tasks are factors in determining the performance of the system. If the systems under consideration are batch-?processing systems, the performance criterion is usually job throughput rate. Tdotable analyses of these systems have been performed by Gaver
[7], Easkett [2], and Boyd [3]. An underlying assumption of the models used in these studies is that the CPU tasks and 1/0 tasks of an individual job aye executed sequentially;.that ls, for a given job in the system model, "no provision is made to allow concurrency of CPU tasks and I/0 tasks. The purpose of this study 3.s to construct a model which allm?s this type of concurrency, then to investigate its effects on job throughput rate under various algorithms of resource allocation.l The basic job and system models are defined. in the following section. Also in that section,- two important parameters Nilaich relate to the load of the system and the con-currency of tasks within a job. are defined and discussed: In section III, three system models vahich include nonpreemptive and preemptive CPU schedules axe outlined. Finally in section IV, numerical results axe presented along; ~,Yith observations based on these results.

2. The Model

2.1 Jab Model.

University of Minnesota Page 1 Dec 31, 1974

Page 2 of 17

A Model of Concurrent Tasks Within Jobs of a Multiprogramming System

Since the purpose of this paper is to investigate the effects of eoncurrency within a job on system throughput, the job model must be constructed such that the overlap of CPU tasks and I/4 tasks within the job ran. be conveniently represented. Figure 2.1 depicts the time behavior of a fob with at most a siL:-le I/(1 task overlap ped with a CPU task in a uniprogram-m;ng system; that is, when there is no competition for the processors. It is assumed that a job consists of a series of alternating CPU and I/0 tasks. Furthermore it'is assumed that the job always begins and ends with a CPU task.

1 For. purposes of this paper,-conourrency is only considered between CPU tasks and T; 0 ta:tks of a job. However, the model used here 1a. modifiable so as to apply to any concurrent tasks and thus may be applicable to a la...