Instruments is, without a doubt, the most powerful profiling tool that I’ve ever used. I cannot say this too strongly. If you aren’t using Instruments to examine and explore your applications, you’re doing it wrong.
Instruments provides a number of tools (somewhat confusingly also called “Instruments”) to track a huge number of application features. This lets us track everything from CPU usage and memory allocation to energy usage and changes in our layout constraints. We can even compare performance across multiple runs, letting us easily see how changes to the code affecting our application’s performance.
To run Instruments, just select the Project > Profile menu item. In the popup window, select the template you wish to use (see Figure 3), and you’re off and running.
Unfortunately, each instrument is capable of collecting a massive amount of information, and displaying it in multiple ways. Learning how to sift through the information to find the important bits is something of an art. However, the more effort you put into learning how to use Instruments, the more powerful it becomes.