DTrace your Macintosh
By Calum-Oracle on Aug 07, 2006
From the OSX Leopard sneak peek:When you need a bit more help in debugging, Xcode 3.0 offers an extraordinary new program, Xray. Taking its interface cues from timeline editors such as GarageBand, now you can visualize application performance like nothing you’ve seen before. Add different instruments so you can instantly see the results of code analyzers. Truly track read/write actions, UI events, and CPU load at the same time, so you can more easily determine relationships between them. Many such Xray instruments leverage the open source DTrace, now built into Mac OS X Leopard.
Cool or what? Now, if they'll just open source their GUI so we can reciprocate by including it in OpenSolaris... :)