Editing Systems engineering (section)

===Performance engineering===
{{Main|Performance engineering}}
[[Performance engineering]] is the discipline of ensuring a system meets customer expectations for performance throughout its life. Performance is usually defined as the speed with which a certain operation is executed or the capability of executing a number of such operations in a unit of time. Performance may be degraded when operations queued to execute are throttled by limited [[system capacity]]. For example, the performance of a [[packet-switched network]] is characterized by the end-to-end packet transit delay or the number of packets switched in an hour. The design of high-performance systems uses analytical or simulation modeling, whereas the delivery of high-performance implementation involves thorough performance testing. Performance engineering relies heavily on [[statistics]], [[queueing theory]], and [[probability theory]] for its tools and processes.