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Ruby JIT Hacking Guide / RubyKaigi 2023
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Takashi Kokubun
May 13, 2023
Programming
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10k
Ruby JIT Hacking Guide / RubyKaigi 2023
Ruby JIT Hacking Guide
https://rubykaigi.org/2023/
Takashi Kokubun
May 13, 2023
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Transcript
Ruby JIT Hacking Guide @k0kubun
@k0kubun
RJIT ERB Haml Slim I maintain
What's JIT?
Ruby JITs MJIT Ruby 2.6
Ruby JITs YJIT Ruby 3.1 MJIT Ruby 2.6
Ruby JITs YJIT Ruby 3.1 MJIT Ruby 2.6 RJIT Ruby
3.3
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
Ruby 3.2 YJIT
Ruby 3.3 YJIT
Using YJIT • Install Rust and then build Ruby •
Use --yjit or export RUBY_YJIT_ENABLE=1
Ruby JIT Hacking Guide
Ruby Hacking Guide
Ruby JIT Hacking Guide JIT JIT
How Ruby JIT works Ruby
How Ruby JIT works 1 + 2 Ruby Abstract
Syntax Tree
How Ruby JIT works 1 + 2 putobject 1 putobject
2 opt_plus leave Ruby Abstract Syntax Tree Instruction Sequence (Bytecode)
How Ruby JIT works 1 + 2 putobject 1 putobject
2 opt_plus leave Ruby Abstract Syntax Tree Instruction Sequence (Bytecode) Machine Code
x86_64 assembly
• Read asm comments •--yjit-dump-disasm •--rjit-dump-disasm x86_64 assembly
• mov: assignment instruction • esi: register for stack[0] x86_64
assembly stack[0] = 3
x86_64 assembly • mov: assignment instruction • edi: register for
stack[1] stack[0] = 3 stack[1] = 5
x86_64 assembly • add,sub: arithmetic instruction • rax: temporary register
stack[0] = 3 stack[1] = 5 temp = stack[0] temp -= 1 temp += stack[1]
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
x86_64 encoding
x86_64 encoding opv86: https://hikalium.github.io/opv86/
x86_64 encoding opv86: https://hikalium.github.io/opv86/
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
Building JIT is fun
k0kubun/ruby-jit-challenge Ruby JIT Challenge
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
Optimizing Ruby JIT
Side exits side exit
Method rede fi nition Rede fi nition Hook Invalidate
Method rede fi nition Rede fi nition Hook Invalidate side
exit
Constant rede fi nition
Register allocation: Stack 0: rsi 1: rdi 4: r10 2:
r8 3: r9 VM stack
Register allocation: Stack 0: rsi 1: rdi 4: r10 2:
r8 3: r9 VM stack
Register allocation: Local variables • Spill registers on C function
calls • Binding • debug_inspector API
Polymorphic method cache
Splitting
Method inlining
Conclusion • Enjoy custom JIT development • Let's make YJIT
the best Ruby JIT