Instruments (formerly Xray) is an application performance analyzer and visualizer, integrated in Xcode 3.0 and later versions of Xcode. It is a developer tool included in Apple Mac OS X v10.5 and later versions of Mac OS X, built on top of the DTrace tracing framework from OpenSolaris and ported to Mac OS X.
Instruments shows a time line displaying any event occurring in the application, such as CPU activity variation, memory allocation, and network and file activity, together with graphs and statistics. Group of events are monitored via customizable "instruments", which have the ability to record user generated events and replay (emulate) them exactly as many times as needed, so a developer can see the effect of code changes without actually doing the repetitive work. The Instrument Builder feature allows the creation of custom analysis instruments.
Built-in instruments can track