Many programmers, when they start to work in Ruby, are surprised to discover the GIL — the Global Interpreter Lock, which ensures that only one thread can run at a time. For people used to working with threads on other systems, it’s hard to come to grips with the GIL. Why does it exist, what can we do to get around it, and how to Ruby developers go about their work when it exists? In this talk, Jerry D’Antonio discusses the GIL, and why many of the things you thought were true about it probably aren’t. He then points to other languages with high-quality concurrency tools, and discusses his efforts to bring these into the Ruby world.