Ruby JIT Hacking Guide / RubyKaigi 2023

Ruby JIT Hacking Guide
https://rubykaigi.org/2023/

Transcript

1. Ruby JIT
   
   
   Hacking Guide
   @k0kubun
   

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2. @k0kubun
   

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3. RJIT ERB
   Haml Slim
   I maintain
   

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4. What's JIT?
   

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5. Ruby JITs
   MJIT
   Ruby 2.6
   

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6. Ruby JITs
   YJIT
   Ruby 3.1
   MJIT
   Ruby 2.6
   

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7. Ruby JITs
   YJIT
   Ruby 3.1
   MJIT
   Ruby 2.6
   RJIT
   Ruby 3.3
   

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8. Railsbench
   Speedup relative to 2.5 No JIT (s/s)
   0
   0.5
   1
   1.5
   2
   Ruby 2.5 Ruby 2.6 Ruby 2.7 Ruby 3.0 Ruby 3.1 Ruby 3.2 Ruby 3.3
   1.93
   1.85
   1.54 1.59
   1.2
   1.25
   1.08
   1.05
   1.07
   1.26
   1.24
   1.12
   1.09
   1.05
   1.07
   1
   No JIT MJIT / RJIT YJIT
   

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9. Ruby 3.2 YJIT
   

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10. Ruby 3.3 YJIT
    

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11. Using YJIT
    • Install Rust and then build Ruby
    
    
    • Use --yjit or export RUBY_YJIT_ENABLE=1
    

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12. Ruby JIT Hacking Guide
    

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13. Ruby Hacking Guide
    

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14. Ruby JIT Hacking Guide
    JIT
    JIT
    

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15. How Ruby JIT works
    Ruby
    

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16. How Ruby JIT works
    1
    +
    2
    Ruby
    Abstract
    

    Syntax
    

    Tree
    

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17. How Ruby JIT works
    1
    +
    2
    putobject 1
    
    
    putobject 2
    
    
    opt_plus
    
    
    leave
    Ruby
    Abstract
    

    Syntax
    

    Tree
    Instruction
    

    Sequence
    

    (Bytecode)
    

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18. How Ruby JIT works
    1
    +
    2
    putobject 1
    
    
    putobject 2
    
    
    opt_plus
    
    
    leave
    Ruby
    Abstract
    

    Syntax
    

    Tree
    Instruction
    

    Sequence
    

    (Bytecode)
    Machine
    

    Code
    

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19. x86_64 assembly
    

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20. • Read asm comments
    
    
    •--yjit-dump-disasm
    
    
    •--rjit-dump-disasm
    x86_64 assembly
    

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21. • mov: assignment instruction
    
    
    • esi: register for stack[0]
    x86_64 assembly
    stack[0] = 3
    

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22. x86_64 assembly
    • mov: assignment instruction
    
    
    • edi: register for stack[1]
    stack[0] = 3
    
    
    stack[1] = 5
    

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23. x86_64 assembly
    • add,sub: arithmetic instruction
    
    
    • rax: temporary register
    stack[0] = 3
    
    
    stack[1] = 5
    
    
    temp = stack[0]
    
    
    temp -= 1
    
    
    temp += stack[1]
    

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24. x86_64 assembly
    • jo: jump if over
    fl
    ow
    
    
    • rsi: register for stack[0]
    stack[0] = 3
    
    
    stack[1] = 5
    
    
    temp = stack[0]
    
    
    temp -= 1
    
    
    temp += stack[1]
    
    
    jump if overflow
    
    
    stack[0] = temp
    

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25. x86_64 encoding
    

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26. x86_64 encoding
    opv86: https://hikalium.github.io/opv86/
    

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27. x86_64 encoding
    opv86: https://hikalium.github.io/opv86/
    

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28. Calling a custom JIT
    Ruby 3.2 Ruby 3.3+
    1. Run Ruby with --mjit=pause --rjit=pause
    2. Override RubyVM::MJIT.compile RubyVM::RJIT#compile
    3. Call RubyVM::MJIT.resume RubyVM::RJIT.resume
    

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29. Building JIT is fun
    

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30. k0kubun/ruby-jit-challenge
    Ruby JIT Challenge
    

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31. Ruby JIT Challenge
    Hashtag: #ruby-jit-challenge
    Speedup relative to No JIT (s/s)
    0
    3
    6
    9
    12
    No JIT RJIT YJIT Ruby JIT
    11.08
    6.31
    3.75
    1
    Fibonatti benchmark
    

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32. Optimizing Ruby JIT
    

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33. Side exits
    side exit
    

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34. Method rede
    fi
    nition
    Rede
    fi
    nition Hook
    Invalidate
    

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35. Method rede
    fi
    nition
    Rede
    fi
    nition Hook
    Invalidate
    side exit
    

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36. Constant rede
    fi
    nition
    

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37. Register allocation: Stack
    0: rsi
    1: rdi
    4: r10
    2: r8
    3: r9
    VM stack
    

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38. Register allocation: Stack
    0: rsi
    1: rdi
    4: r10
    2: r8
    3: r9
    VM stack
    

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39. Register allocation: Local variables
    • Spill registers on C function calls
    
    
    • Binding
    
    
    • debug_inspector API
    

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40. Polymorphic method cache
    

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41. Splitting
    

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42. Method inlining
    

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43. Conclusion
    • Enjoy custom JIT development
    
    
    • Let's make YJIT the best Ruby JIT
    

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