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MULfiPROGlWkrNG IN A PAGE ON DEMAND COMPUtER SYSTEM: PERFOmwtCE MODELS AND EVALUMIOB

by

DAVID SCHilARTZ

SUBMITTED IN PARTIAL FULFILIJIENT OF THE RBtUIREMEB!S

FOR THE DEGREE OF

MASTER OF SCIENCE

ELECTRICAL ElGlNEERING

at the

MASSACHusETTS INSTITUTE OF TECHNOLOGY

JUNE 1973

Si~:~~U:orEl.eetrTh'&i-EngI;nee~-;-MaY !J.;p7:;; - - --

Certified by-=:; ~~7;P--.~""~---- - - - - - - - -- / ~is Supervisor

Accepted by -'- _ ~-=L~- ...,._~_~ - - Chairman, Departmental caiiihtee on lz-r&c1uate Students

MULTIPROGRAMiING IN A PAGE ON T)D,!fFD COMPUT ER SYSTEM: PERFORMANCE MODE LS DEVALUATION

by

DAVID SCHWA01Z

Submitted to the Department of Electrical Engineering on June 1, 1973, in parti-E fullment of the

requirements for the Degree of Master of Science

ABS TRACT

The System Process Model (SPM) is used to represent behavior of the multiprogramming module of a compnter system operating under a demand paging strategy. It models the system as a network of states and assoc- iated queues. The level of multiprog:rnaing is varied by changing the average n-unber of pages that users are permitted in main memory. De- vices are explicitly characterized by parameters representative of their behavior, and sample programs run unde2e CP-6( are parameterized in terms of I/O and paging activity for use in representing jobs in the system.

With the intention of using this model for performance projection, a notential oroblem characteristi of such virtual memory systems is discussed. The thrasingr -oroblem is defined as the less than optimal ise of system resources resulting from excessive competition for primary memory. Novel definitions for pinpointing this degredation are prorosed.

SPM is then used as a vehicle to analyze the operations of a CP-67 like system. Performance is predicted under full load for various levels of multiprogramming and optimal performance as well as thrashing degreda- tion are quantified. Scheduling is shown ;o be a key tecimique for improv- ing system performance as well as iOprovements in device technology. An interesting characteristic of the system, the law of diminishing returns to scale, is uncovered as a result of the investigations.

Analysis is performed with both analytical and simualation models. This permits comparative analysis of the methods based on some interest- ing and revealing criteria. The techniques, which are of both theoret- ical and oractical value in the area of performance evaluation, are rat- ed on their approach to modeling SPM.

ACKNOWLEDGEMENTS

I would like to express my gratitude to all of the sincere people

at both MIT and Harvard that have been so helpful in the preparation of

this manuscript.

At MIT, I extend first thanks to Professor S.E. Madniek, my thesis

supervisor. He introduced me to the area of computer system modeling,

thus providing the initial stimulus for this research. He also created

the atmosphere of friends hip and understanding so important to the

overall effort. I would like to thank Professor J. Donovan for his

insight and continuing support of the research. In addition, I would

like to extend thanks to Professor D. Larson, my graduate advisor,

for his assistance in the Markov-state analysis that was carried out.

At Harvard, Professor U.0 Gagliardi and J.P. Buzen provided an

excellent environment for the study of computer system performance. I

would like to thank them for their constructive criticism as well as

the interesting literature in the field that ther introduced to me. I

would especially like to thank Jeff Buzen for his assistance in analyzing

the queuing network model.

Words meaningful enough to thank my wife, Sharon, for her lasting

patience and assistance are difficult to find. I thank her especially

for help in the final preparation of the paper. She has been my ultimate

queuing state, and I dedicate this thesis to her.

TABLE OF CONTENTS

CHAPTF-FR/SECTION

TITLE PAGE ................... .....

ABSTRACT .........................---

ACKNOWLEDGEMENTS ....................

TABLE OF CONTENTS ..................

LIST OF FIGURES ....................

LIST OF TABLES .....................

SYNOPSIS AND ORGANIZATIONAL REMA1RKS

CHAPTER 1

INTRODUCTION...........

1.1 The Need for System Modeling 1.2 Approaches to System Analysis:

Analytical and Simulation Models 1.2.1 Analytical Models .... 1.2.2 Simulation Models ....

1.3 Thesis Objective ...............

CHAPTER 2

2.1 2.2 2.3 2.4

WHO'S WHO IN COMPIIPUTER MODELING.......

Overview of the Target System ........ Analytical Modeling . . . . Simulation Modeling .................. Work Relevent to this Thesis .........

2.4.1 The Work of J. Smith 2.4.2 The Work of A. Sekino ...... 2.4.3 The Work of J. Buzen, D. Rice,

and C. Moore ............... 2.4.4 The Work of T. Schreiber ...

PAGE

21

21

25 27 31 32 33

34 36

--.--...---- 0

--- --.------ 0

PAGE CHAPTER 3

MULTIPROGRAINthG IN A PA E ON DEMAND COMPUTER SYSTEM ATM A CONCEPTUAL "OEL OR PERFORMANCE EVALUATION...........

3.1 Page on Demand Virturi Memory Systems 3.2 The Thrashing Probler.: Novel, Quantative

Definitions ... ............

3.2.1 The M1ltip-ogramning Cost of Job Execution ...............

3.2.2 Averag. CPU Utilization .... 3.3 The System Process Model: A Conceptual

Model of Computer Behavior 3.3.1 Sample Program Behavior

3.3.2 The I/O Sub-ystems ........... 3.3.2.1 Thc Paging Drum .. . 3.3.2.2 The 1,0 Disk ........ 3.3.2.3 Scheduling the I/O

Subsystems ...... 3.3.3 Basic Modeling Assumptions 3.3.4 A Derivation of System

Throughput for SP14 ...

37

37

41

41 43

44 45 4) 49 50

50 51

52

CHAPTER 4

ANALYTICAL MODELS FOR PER1ORMANCE ANALYSIS

4.1 Mathematical Model Selection .......... 4.2 Independent Continuous time Markov Models.

4.2.1 System Representation ........ 4.2.2 Specification of the Composite

Cost Function ................ 4.2.3 The Continuous Time Markov

Models ....................... 4.2.4 The Steady State Solutions ... 4.2.5 Applying the Solutions .......

4.3 The Dual Facility Continuous Time Markov Model ..................................

4.3.1 System Representation ........ 4.3.2 The Steady State Solution .... 4.3.3 Applying tbe Solutions .......

4.4 The Queuing Network i'del......... 4.4.1 System Representation ........ 4.4.2 Paramet er:Izat ion of the Network 4.14.3 The Steady State Solution .... 4.4.4 Applying the Solution

54 55 55

58

62 65 66

68 68 70 70

75 76 79 81

PAGE CHAPTER 5

SIML'ATION: AN APPROACH TO lYSTEM PERFOR::ANCE ANALYSIS ..................... ,.v........ . 83

5.1 Introduction .......................... 83 5.2 Characteristics and Problems of

Simulation ........................... 84

5.3 Simulation of the Systemn Process Model.. 87 5.3.1 Statement of the Problem .... 87 5.3.2 Approach Tahen in Building the

Model ................... . 89

5.3.3 Table Definitions ........ 94 5.3.4 Block Diagrams 94

5.4 Extensions ............................. 97 5.4.1 Detailed I/O Subsystems ..... 97 5.4.2 Arbitrary Service Disciplines. 101 5.4.3 Priority Schedulin . . 102

CHAPTER 6

PERFOPJMNCE PROJECTION: THE RESULTS.... 1 03

6.1 Load and Performance Measures 103 6.2 Performance Prediction for the Multi-

programming Moul. 105 6.2.1 Multiprogramming Idle Time

Analysis .................... 107 6.2.2 Average CPU Utilization

Analysis .................... 112 6.3 Discussion of Results .................. 121 6.4 Com-parison of the Results for the Alter-

native Modeling Techniques ........... 1 23

CHAPTER 7

CONCLUSIONS ............... 125

7.1 A Comparison of the Modeling Techniques. 125

7.2 The Scope of SPM: Future Work ........ 128 1307.3 Final Ccnents.......................

APPENDIX A THE CONTITUOUS TIE MARKOV-STATE ANALYSIS PROGRAM.. ........ . . .......... 12

APPENDIX B THLE QUEUIIG 1EiWORK ANALYSTS PROGRM ... 151 APPENDIX C THE GENERAL PURPOSE SYSTEMS SIUL3jATION. 158

165 BIBLIOGRAPHY

7

LIST OF FIGURES

FIGURE PAGE

2-. Fesource Partitioning in Operating System Overview ... 22

2-2 Overview of Operating System Operations .............. 23

2-3 Operating System Overview Partitioned. By Models Used For Analysis ....................................... 24

3-1 S-unple Program Paging Behavior as a Function of Real Nemory Available ......... ................. 47

3-2 Number of Page Faults as a Function of the Degree of Miltiprogramming ....................

4-1 Conceptual Model of Process Activity in a Multipro- graiming Environment with IO Wait .... 50

4-2 Conceptual Model of Process Activity in a Multipro- gramming Environment with Page Wait.................... 57

4-3 Markov Digraph for the State Transitions in a Multi- programming Environment with I/O Blocking................. 65

4-4 Markov-Digraph for the State Transitions in a Multi- 64 programming Environment with Page Blocking ...........

4-5 Conceptual Model of Process Activity in a Multipro- gram-ming Environment with Page and