HOW RUBY EXECUTES JIT CODE: THE HIDDEN MECHANICS BEHIND THE MAGIC

Summary from the TLDR Web Dev newsletter

This article explains the inner workings of Ruby's JIT (Just-In-Time) compilers. JIT-compiled machine code lives alongside the original bytecode in Ruby's Instruction Sequences (ISEQs), with Ruby deciding which to execute based on call frequency. Methods must be called 25+ times to be profiled and 30+ times to be compiled to native code. When JIT code's assumptions are violated, Ruby "de-optimizes" by falling back to the interpreter to guarantee correctness.