Software performance is one of software quality attributes, it equal to efficiency which define in latest ISO 9126 standard :
This characteristic is concerned with the system resources used when providing the required functionality. The amount of disk space, memory, network etc. provides a good indication of this characteristic. As with a number of these characteristics, there are overlaps. For example the usability of a system is influenced by the system's Performance, in that if a system takes 3 hours to respond the system would not be easy to use although the essential issue is a performance or efficiency characteristic.
In the standard 1061 of IEEE, the performance also described as efficiency and has the similar description. These are two most general and authoritative definition about performance in software, but as the evolving of software engineering , the people call it as performance more often other than efficiency.
No matter it been called performance or efficiency , it include three important factors at least and they should be constant :
Or say the latency , means the software run how fast within the limit HW configuration.
In different types of systems , throughput can be explained these three kinds of metrics:
Often used in opening system , which be measured by the arrival rate
often used in network system ,it is also a metric about network throughput which can indicate the usage of network bandwidth in other types of system
Often used in terminal system, means how many users and their activities can be done in a quite small timeframe
How many resources be consumed per user or per transaction and how many left room for current HW, also predict how many resources to be devoted as business growing.
The DR .Connie Smith is the founder of performance engineering, she defined the terminology as :
Software Performance Engineering (SPE) is a systematic, quantitative approach to the cost-effective development of software systems to meet performance requirements. SPE is a software-oriented approach that focuses on architecture, design, and implementation choices.
Totally , performance engineering is a series of activities to meet performance requirements , that is the reason why the performance be engineered . Also performance engineering is a part of software engineering whether in waterfall or iteration models. And at the same time , Subtasks of performance engineering can be integrated into the whole software project lifecycle:
The SPE process begins early in the software development life cycle and uses quantitative methods to identify satisfactory designs and to eliminate those that are likely to have unacceptable performance before developers invest significant time in implementation. SPE continues through the detailed design, coding and performance and load testing phases to predict and manage the performance of the evolving software as well as monitor and report actual performance versus specifications and predictions. SPE methods encompass: performance data collection; quantitative performance analysis techniques; prediction strategies; management of uncertainties; data presentation and tracking; performance testing, stress and load testing, model verification and validation; critical success factors; and performance design principles, patterns and antipatterns
This section give us the performance engineering not only in testing , but even in design and architecture, the following figure shows my understanding and thinking for this:
More SPE details info you can access the Smith's company website :
3.let's build a professional performance engineering forum in China