Connie U. Smith

Software performance antipatterns

A pattern is a common solution to a problem that occurs in many different contexts. Patterns capture expert knowledge about “best practices” in software design in a form that allows that knowledge to be reused and applied in the design of many different types of software. Antipatterns are conceptually similar to patterns in that they document recurring solutions to common design problems. They are known as antipatterns because their use (or misuse) produces negative consequences. Antipatterns document common mistakes made during software development as well as their solutions. While both patterns and antipatterns can be found in the literature, they typically do not explicitly consider performance consequences. This paper explores antipatterns from a performance perspective. We discuss performance problems associated with one well-known design antipattern and show how to solve them. We also propose three new performance antipatterns that often occur in software systems.

PASA SM : a method for the performance assessment of software architectures

Architectural decisions are among the earliest made in a software development project. They are also the most costly to fix if, when the software is completed, the architecture is found to be inappropriate for meeting quality objectives. Thus, it is important to be able to assess the impact of architectural decisions on quality objectives such as performance and reliability at the time that they are made.This paper describes PASA, a method for performance assessment of software architectures. It was developed from our experience in conducting performance assessments of software architectures in a variety of application domains including web-based systems, financial applications, and real-time systems. PASA uses the principles and techniques of software performance engineering (SPE) to determine whether an architecture is capable of supporting its performance objectives. The method may be applied to new development to uncover potential problems when they are easier and less expensive to fix. It may also be used when upgrading legacy systems to decide whether to continue to commit resources to the current architecture or migrate to a new one. The method is illustrated with an example drawn from an actual assessment.

Performance Engineering Evaluation of Object-Oriented Systems with SPE*ED

Although object-oriented methods have been shown to help construct software systems that are easy to understand and modify, have a high potential for reuse, and are relatively quick and easy to implement, concern over performance of object-oriented systems represents a significant barrier to its adoption. Our experience has shown that it is possible to design object-oriented systems that have adequate performance and exhibit the other qualities, such as reusability, maintainability, and modifiability, that have made OOD so successful. However, doing this requires careful attention to performance goals throughout the life cycle. This paper describes the use of SPE·ED, a performance modeling tool that supports the SPE process, for early life cycle performance evaluation of object-oriented systems. The use of SPE·ED for performance engineering of object-oriented software is illustrated with a simple example.

A performance model interchange format

Abstract A performance model interchange format (PMIF) provides a mechanism whereby system model information may be transferred among performance modeling tools. The PMIF allows diverse tools to exchange information and requires only that the importing and exporting tools support the PMIF. This paper presents the definition of a PMIF by describing a meta-model of the information requirements and the transfer format derived from it. It describes how tool developers can implement the PMIF, how the model interchange via export and import works in practice, and how the PMIF can be extended. A simple case study illustrates the format. The paper concludes with the current status of the PMIF, lessons learned, some suggestions for extensions, and current work in progress.

Information Requirements for Software Performance Engineering

The design and construction of future software systems will require the integration of software analysis and design methods with Software Performance Engineering (SPE) [Smith and Williams, 1990]. Software methods provide rules and guidelines for performing systems analysis and designing software. Software Performance Engineering [Smith, 1990] is a method for constructing software systems that meet performance goals. SPE includes techniques for gathering data, coping with uncertainty, constructing and evaluating performance models, evaluating alternatives, and verifying and validating results. It also includes strategies for the effective use of these techniques.

Performance Model Interchange Format (PMIF 2): A comprehensive approach to Queueing Network Model interoperability

The Performance Model Interchange Format (PMIF) provides a mechanism for transferring the system model information among performance modeling tools requiring only that the tools either internally support PMIF or provide an interface that reads/writes model specifications from/to a file. This paper presents the latest version of the specification (PMIF 2): a metamodel defining the information requirements and the corresponding XML schema. It defines the semantic properties for a pmif.xml interchange, the prescribed validation order, errors and warnings, and a tool and Web service implementation. Import and export prototypes for two different types of tools prove the concept. Generally available examples are used for repeatability.

Interchange Formats for Performance Models: Experimentation and Ouput

XML-based interchange formats for performance models provide a mechanism whereby performance model information may be transferred among modeling tools. For example, the PMIF allows diverse tools to exchange queueing network model information. Formats have also been defined for the interchange of LQN, UML, Petri Nets, and others. These formats specify the model and a set of parameters for one run. For model studies, however, it is useful to be able to specify multiple runs, or experiments, for the model. This paper presents an XML interchange schema extension for defining a set of model runs and the output desired from them. It has the expressive power to specify iterations, alternations, assignments of values, actions based on model results and more. Examples illustrate how the experiment interchange extension can be used with a wide variety of performance modeling paradigms. A prototype proves the concept.

Model Interchange Format Specifications for Experiments, Output and Results

XML-based interchange formats for performance models provide a mechanism whereby performance model information may be transferred among modeling tools. Formats have been defined for the interchange of queueing network models (QNM), layered queueing networks, UML, Petri nets (PNs) and others. These formats specify the model and a set of parameters for one run. For model studies, however, it is useful to be able to specify multiple runs, or experiments, for the model; to collect model output; and to present it in a useful, readable format for analysis and presentation. This paper presents a performance model interoperability framework that brings together performance model interchange formats and experiment specifications with the automatic generation of performance analysis results for presentation and publication. We present the output specifications, the requirements for the types of results to be supported, the issues in the output-to-results transformation, the results specifications and several prototype implementations that demonstrate the viability of the approach. We apply the approach to two distinct modeling paradigms: QNM and PN models. Several proof of concept experiments demonstrate the framework.

Performance Model Interchange Format: Semantic Validation

A Performance Model Interchange Format (PMIF) provides a mechanism whereby system model information may be transferred among queueing network model (QNM) based modeling tools. The PMIF allows diverse tools to exchange information and requires only that those tools provide importing/exporting mechanisms from/to the PMIF. The XML specification of the PMIF allows implementers to use widely available tools to parse the XML file, check the syntax, and simplify the translation to/from the XML format. Those tools, however, do not know the semantics of a QNM so they cannot check the XML to ensure that it contains a valid QNM. This paper presents the study of the validations needed to carry out such a semantic analysis, and the development of a semantic validation tool that can be used by any developer who wants to implement PMIF import/export mechanisms.

A web service for solving queuing network models using PMIF

A performance model interchange format (PMIF) is a common representation for queuing network model data that can be used to move models among modeling tools. This paper demonstrates how Web services can be used to facilitate the use of modeling tools that can interface with the PMIF. The paper describes the design and implementation of a PMIF Web service for the modeling tool Qnap. Additionally, it shows experimental results that prove the viability of such a Web service.