Want to get started with YJIT? See the latest README for details. The short version goes:

    # If you have a YJIT-capable Ruby installed, run with the --yjit flag
    ruby --yjit my_file_to_make_faster.rb
    RUBYOPT="--yjit" rails server

    # Any Ruby 3.1.0 or later has YJIT support
    rvm install ruby-3.1
    ruby-build 3.1.0 ~/.rubies/ruby-3.1.0
  

YJIT Resources

• Lazy Basic Block Versioning whitepaper
• RubyKaigi 2021 talk: YJIT: Building a New JIT Compiler Inside CRuby
• RubyKaigi 2022 talk: Stories from Developing YJIT
• Latest YJIT README in CRuby
• Latest YJIT Hacking Concepts in CRuby
• For deep details about Ruby bytecode, Kevin Newton's Advent of YARV is fantastic

You can install Ruby 3.1.0 or higher to get the most recent release of YJIT. 3.2.0 or higher is strongly preferred for long-running servers.

Snippets to disassemble chunks of Ruby code:

    # To disassemble Ruby bytecode:
    puts RubyVM::InstructionSequence.disassemble(method :whatever_method)

    # Ruby bytecode plus YJIT assembly language (only on dev YJIT):
    puts RubyVM::YJIT.disasm(method :whatever_method)

    # If you want to do YJIT disassembly, you'll need to run with YJIT
    ruby --yjit my_disassembly_test.rb

    # And when you build Ruby, you'll need to turn on dev YJIT:
    ./configure --yjit-enable=dev
  

You can find more BBV and YJIT talks and papers in the CRuby YJIT README.

Slides from my talk