A good profiler is essential to making faster code.

Vernier is a new profiler for CRuby 3.2+ which uses new techniques and new APIs in Ruby with more detailed and more accurate results than existing tools. It supports threads (including N:M), ractors, GVL activity, Garbage Collection, idle time, and more!

In this talk I'll explain the challenges we faced with existing profilers, tradeoffs and changes previously made to stackprof, the new techniques Vernier uses, and how more visibility in what code is run may change how we write Ruby for the better.