Design and Use of a Program Execution Analyzer

Execution analyzers are used to improve the performance of programs, operating systems, and hardware systems. This paper presents a general overview of these tools, especially those designed for use by application programmers. The design tradeofis of a wide variety of execution analyzers are examined. In addition, the design and use of a new execution analyzer are presented; its purpose is to assist in the optimization of highly modular PL/I programs. A n execution analyzer is a tool for measuring specific details about the execution of programs , for example, pinpointing where a program spends its time, identifying what program paths are actually executed, or identifying what subroutines are called. An execution analyzer can reveal surprising facts about a program that a programmer can use to improve the program, sometimes dramatically. This paper discusses the design of a program execution analyzer. A general definition of this class of software tools is presented, and a wide variety of techniques used by existing analyzers are surveyed. In addition, the design and use of a new program execution analyzer that we call the Experimental PL/I Execution Analyzer (EPLEA)' are discussed. The purpose of EPLEA is to support the optimization of execution time of highly modular PL/I programs. Experience with this tool is presented as a case study. The casual reader should gain a better understanding of the value and use of execution ana-lyzers. The general-purpose architecture and survey of techniques should benefit anyone designing a special-purpose execution analyzer or evaluating existing analyzers. The case study should be of particular interest to PL/I programmers. Although the primary intent of this paper is to discuss execution analyzers for use by application programmers, many of the design tradeoffs discussed apply as well to operating system performance tools and hardware monitors. Measurement tools for operating systems are readily available2"' and have received good coverage in the literature ."-'' Hardware monitors have received less attention and will be mentioned briefly. Many more program execution analyzers have been dceloped than are mentioned here. This is certainly a testament to their usefulness, but it is also a result of the wide variety of user requirements, programming languages, and system dependencies that they must deal with. In fact, it is the need for a unique measurement tool that has attracted the author to this area of research. OCopyright 1983 by International Business Machines Corporation. Copying in printed form for private use is …