Takeaways

Let’s review what you just learned about profiling:

• Use ruby-prof for profiling. Get better profile visualization with KCachegrind/QCachegrind.

• Profiling is the only reliable way to understand what is slow in your application. Unfortunately it doesn’t tell you how to optimize.

• Profiling and visualization tools are prone to double counting. You must carefully examine your profile to draw the right conclusions.

• Remember little details that can make your profiles invalid. Turn off GC for CPU profiling.