The Xcode instruments allow you to dynamically trace and profile the performance of your Mac OS X, iPhone, and iPad applications. You can also create your own Instruments using DTrace and the Instruments custom builder.
We do not cover DTrace in this book, if you are interested in reading a bit more about this area; please consult the Apple Developer Documentation at the following: http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man1/dtrace.1.html#//apple_ref/doc/man/1/dtrace. DTrace has not been ported to iOS, so it is not possible to create a custom instrument for devices running iOS.
Through the use of instruments, you can achieve the following: