Whether your application is concurrent or not, there's insight to be gained from Ruby's threading support.
This talk demonstrates building a light-weight sampling profiler in pure Ruby. The techniques are simple enough to integrate into almost any application, and fast enough for even a production environment. If you've ever wondered exactly what your application is doing at any given moment, this will show you how to find out.
Along the way we'll expose gotchas and pitfalls of thread introspection on the many versions and implementations of Ruby. Based on experience implementing thread profiling for New Relic, we'll also touch on how to debug and work around problems when they come up.