Exit(ing) through the YJIT

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EXIT(ing) Through the YJIT

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Eileen M. Uchitelle Twitter / GitHub: @eileencodes Mastadon: @[email protected]

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EXIT(ing) Through the YJIT

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What is a JIT?

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What is a JIT? "Just in time" compiler

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MJIT "Method-Based" JIT

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YJIT "Yet Another" JIT

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def call_method(arg) if arg == "hello" puts arg else puts "bye" end end YJIT only compiles code that is run

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def call_method(arg) if arg == "hello" puts arg else puts "bye" end end call_method("hello") YJIT only compiles code that is run

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def call_method(arg) if arg == "hello" puts arg else puts "bye" end end call_method("hello") YJIT only compiles code that is run

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def call_method able_to_compile not_able_to_compile end call_method YJIT can compile parts of methods

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def call_method able_to_compile not_able_to_compile end call_method YJIT can compile parts of methods

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def call_method able_to_compile not_able_to_compile end call_method YJIT can compile parts of methods

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How is YJIT implemented?

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MJIT vs YJIT Which to use?

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How can I use YJIT?

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$ docker pull rubylang/ruby:master-debug- nightly-focal Docker Images

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Pre-requisites • autoconf • make • bison • GCC or Clang • libyaml • [email protected] • Rust (for YJIT) • Ruby

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Run autogen $ cd ruby $ ./autogen.sh

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Configure Ruby $ ./configure --prefix=~/.rubies/ruby-yjit --with-openssl-dir=$(brew --prefix [email protected]) --disable-install-doc

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Configure Ruby: Set prefix $ ./configure --prefix=~/.rubies/ruby-yjit --with-openssl-dir=$(brew --prefix [email protected]) --disable-install-doc   

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Configure Ruby: openssl $ ./configure --prefix=~/.rubies/ruby-yjit --with-openssl-dir=$(brew --prefix [email protected]) --disable-install-doc

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Configure Ruby: Disable rdoc $ ./configure --prefix=~/.rubies/ruby-yjit --with-openssl-dir=$(brew --prefix [email protected]) --disable-install-rdoc   

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Install Ruby $ make install

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$ RUBY_YJIT_ENABLE=1 ruby my_script.rb $ ruby --yjit my_script.rb $ ruby --jit my_script.rb Enabling YJIT

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YJIT dev mode $ ./configure --enable-yjit=dev --prefix=~/.rubies/ruby-yjit --with-openssl-dir=$(brew --prefix [email protected]) $ make install

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"Exit" When YJIT is unable to compile

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ar_demo.rb ActiveRecord::Base.establish_connection( adapter: "sqlite3", database: ":memory:") ActiveRecord::Schema.define do create_table :posts, force: true do |t| end end class Post < ActiveRecord::Base end class BugTest < ActiveSupport::TestCase def test_create Post.create! end end

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Running with stats enabled $ bundle exec ruby --yjit-stats ar_demo.rb

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But what does the code look like?

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"We can totally make that work." - Aaron Patterson

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Tracing YJIT Exits

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Tracing exits $ bundle exec ruby --yjit-trace-exits ar_demo.rb

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ar_demo.rb [...] class Post < ActiveRecord::Base def call_method(options) one, two, three = options end end class BugTest < ActiveSupport::TestCase def test_create post = Post.create! post.call_method("hello") end end

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Fixing broken code $ bundle exec ruby --yjit-trace-exits --yjit-call-threshold=1 ar_demo.rb

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How will we use this?

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Optimizing YJIT

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yjit/src/codegen.rs /// Maps a YARV opcode to a code generation function (if supported) fn get_gen_fn(opcode: VALUE) -> Option { let VALUE(opcode) = opcode; let opcode = opcode as ruby_vminsn_type; assert!(opcode < VM_INSTRUCTION_SIZE); match opcode { [...] YARVINSN_send => Some(gen_send), YARVINSN_invokeblock => Some(gen_invokeblock), YARVINSN_invokesuper => Some(gen_invokesuper), YARVINSN_leave => Some(gen_leave), [...]

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yjit/src/codegen.rs asm.jne( counted_exit!( ocb, side_exit, invokesuper_block ).into() );