I gave a talk on using JIT in Ruby 2.6 at Southeast Ruby - a great regional conference with a very friendly, cozy vibe. If you get a chance, I highly recommend going next year! It'll be August 1st and 2nd, 2019.
Wondering about what JIT is, how it works and why you'd use it? Or how to try it out in (currently pre-release) Ruby 2.6? Here are my slides. Don't miss the presenter notes, which have extra detail beyond just what's in the slides.