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Towards Ruby 4 JIT / RubyKaigi 2022
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Takashi Kokubun
September 08, 2022
Programming
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Towards Ruby 4 JIT / RubyKaigi 2022
RubyKaigi 2022
Takashi Kokubun
September 08, 2022
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Transcript
Towards Ruby 4 JIT @k0kubun
@k0kubun Maintain: MJIT, Haml, ERB Shopify team
GitHub Sponsors
Haml 6
Introduction to Ruby JIT
How does Ruby JIT work? Ruby
How does Ruby JIT work? 1 + 2 Ruby Abstract
Syntax Tree
How does Ruby JIT work? 1 + 2 putobject 1
putobject 2 opt_plus leave Ruby Abstract Syntax Tree Instruction Sequence (Bytecode)
How does Ruby JIT work? 1 + 2 putobject 1
putobject 2 opt_plus leave Ruby Abstract Syntax Tree Instruction Sequence (Bytecode) Machine Code
How does Ruby JIT work?
CRuby JIT 1: MJIT
CRuby JIT 2: YJIT
Current CRuby JITs speed.yjit.org
Current CRuby JITs speed.yjit.org
Current CRuby JITs • YJIT • Available since Ruby 3.1
• --jit or --yjit • MJIT • Available since Ruby 2.6 • --mjit
Current CRuby JITs • YJIT • Ruby 3.1: x86_64 only,
no code GC, written in C • Ruby 3.2: arm64 support, (hopefully) code GC, written in Rust • MJIT • Ruby 3.1: Stable-ish, portable, native threads, written in C • Ruby 3.2: Experimental, fork + SIGCHLD, written in Ruby
MJIT in Ruby
None
None
mjit.rb: Secret "standard library" in Ruby 3.2 • mjit.rb •
Even more powerful than TracePoint • You can monkey-patch CRuby JIT • No compatibility guarantee • Every module is private, so const_get is required
BYOJ: Bring Your Own JIT
BYOJ: Bring Your Own JIT • Load and pause MJIT
with --mjit=pause • Define RubyVM::MJIT.compile • Use RubyVM::MJIT.const_get(:C) to hack RubyVM • Call RubyVM::MJIT.resume to start JIT With Ruby 3.2:
YJIT-style JIT • Monkey-patch RubyVM::MJIT.compile
MJIT-style JIT • Monkey-patch RubyVM::MJIT::Compiler.compile
MJIT-style JIT
Everyone is writing CRuby JIT
Benchmarking Ruby JIT
yjit-bench
yjit-bench • yjit-bench has three kinds of benchmarks: 1. Headlining
Benchmarks 2. Other Benchmarks 3. Micro Benchmarks
1. Headlining benchmarks • activerecord • hexapdf • liquid-render •
mail • psych-load • railsbench ✉
2. Other Benchmarks • binarytrees, fankuchredux, nbody • chunky_png •
erubi, erubi_rails • lee • optcarrot • rubykon
3. Micro Benchmarks • 30k_ifelse, 30k_methods • cfunc_itself, str_concat •
fib • getivar, setivar • keyword_args • respond_to
None
Benchmark Your Own JIT • ./run_benchmarks.rb -e “/path/to/ruby --any-option” •
Pass multiple -e options to compare different JITs
Towards Ruby 4 JIT
My wish on Ruby 4 JIT • I want Ruby
4 to be as fast as Java or JavaScript • Ruby 4's performance should be a reason to leave Python
None
More Concrete Examples
None
None
None
Ruby 4 Canary • true is mov-ed (immediate) • No
opt_* VM instruction • Constant folding • Ruby / C method inlining
Ruby 4 Canary’ • Single branch instruction to access @one
• Single register to access two • No heap allocation • No stack frame
None
None
Ruby 4 Canary 2 • 5000050000 is mov-ed (immediate) •
Ruby -> C -> Ruby inlining
How can we get there?
Optimization Challenges 1. Constants 2. Variables 3. Method calls 4.
Garbage collection
1. Constants
1. Constants
1. Constants
1. Constants
1. Constants
1. Constants
1. Constants
1. Constants
2. Variables
2. Variables
2. Variables
2. Variables
2. Variables
2. Variables
2. Variables
2. Variables
2. Variables
2. Variables
2. Variables
2. Variables 2021 2022 (tomorrow)
3. Method calls
3. Method calls
3. Method calls
3. Method calls
3. Method calls
3. Method calls
3. Method calls • Code locality • Method inlining: C
㱻 Ruby • Pass arguments with native ABI • Deoptimization on redefinition or interruption (or TracePoint)
4. Garbage collection
4. Garbage collection
4. Garbage collection
Next Steps • We still have a lot of rooms
for improvements on yjit-bench • More cross-instruction optimizations • More method inlining over Ruby and C
Conclusion • Build your own JIT with Ruby 3.2 •
Benchmark your JIT with yjit-bench