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1.7 Roles and Activities of a Performance Engineer

Like a systems architect, a performance engineer should be engaged in all stages of a software project. The performance engineer is frequently a liaison between various groups of stakeholders, including architects, designers, developers, testers, product management, product owners, quality engineers, domain experts, and users. The reasons for this are:

  • The performance of a system affects its interaction with the domain.
  • Performance is influenced by every aspect of information flow, including

    • The interactions between system components
    • The interactions between hardware elements and domain elements
    • The interactions between the user interface and all other parts of the system
    • The interactions between component interfaces

When performance and functional requirements are formulated, the performance engineer must ensure that performance and scalability requirements are written in verifiable, measurable terms, and that they are linked to business and engineering needs. At the architectural stage, the performance engineer advises on the impacts of technology and design choices on performance and identifies impediments to smooth information flow. During design and development, the performance engineer should be available to advise on the performance characteristics and consequences of design choices and scheduling rules, indexing structures, query patterns, interactions between threads or between devices, and so on. During functional testing, including unit testing, the performance engineer should be alerted if the testers feel that the system is too slow. This can indicate a future performance problem, but it can also indicate that the system was not configured properly. For example, a misconfigured IP address could result in an indication by the protocol implementation that the targeted host is unresponsive or nonexistent, or in a failure of one part of the system to connect with another. It is not unusual for the performance engineer to be involved in diagnosing the causes of these problems, as well as problems that might appear in production.

The performance engineer should be closely involved in the planning and execution of performance tests and the interpretation of the results. He or she should also ensure that the performance instrumentation is collecting valid measurement data and generating valid loads. Moreover, it is the performance engineer who supervises the preparation of reports of performance tests and measurements in production, explains them to stakeholders, and mediates negotiations between stakeholders about necessary and possible modifications to improve performance.

If the performance of a system is found to be inadequate, whether in testing or in production, the performance engineer will be able to play a major role in diagnosing the technical cause of the problem. Using the measurement and testing methods described in this book, the performance engineer works with testers and architects to identify the nature of the cause of the problem and with developers to determine the most cost-effective way to fix it. Historically, the performance engineer’s first contact with a system has often been in “repairman mode” when system performance has reached a crisis point. It is preferable that performance issues be anticipated and avoided during the early stages of the software lifecycle.

The foregoing illustrates that the performance engineer is a performance advocate and conscience for the project, ensuring that performance needs are anticipated and accounted for at every stage of the development cycle, the earlier the better [Browne1981]. Performance advocacy includes the preparation of clear summaries of performance status, making recommendations for changes, reporting on performance tests, and reporting on performance issues in production. Thus, the performance engineer should not be shy about blowing the whistle if a major performance problem is uncovered or anticipated. The performance reports should be concise, cogent, and pungent, because stakeholders such as managers, developers, architects, and product owners have little time to understand the message being communicated. Moreover, the performance engineer must ensure that graphs and tables tell a vivid and accurate story.

In the author’s experience, many stakeholders have little training or experience in quantitative methods unless they have worked in disciplines such as statistics, physics, chemistry, or econometrics before joining the computing profession. Moreover, computer science and technology curricula seldom require the completion of courses related to performance evaluation for graduation. This means that the performance engineer must frequently play the role of performance teacher while explaining performance considerations in terms that can be understood by those trained in other disciplines.

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