JRuby Startup and AOT Thomas E. Enebo (@tom_enebo) Charles O. Nutter (@headius)

• JRuby co-leads • Red Hat Charles Thomas Ruby Java Beer

What is JRuby? An implementation of the Ruby language and Runtime def ruby puts "It is pretty cool..." end

Why JRuby? • Native Threads • Access Java Libraries from within Ruby • The power of Java (GCs, Profiled Opts, Portability) • All the things we know and love about Java….BUT…

…startup time is a problem • Java is not known for short-lived command-line executions • Rubyists constantly run ruby from the command-line • They expect it to be short-lived • This is our perennial issue to solve

Many Ruby Core Classes % jruby -e 1 415 classes/modules defined 300+ come from Ruby source

Many Java Classes • More than 6400 Java classes loaded for -e 1 • Nearly 5000 are from JRuby

• Ruby is a dynamic expression-based language • No ahead of time knowledge of what will load Dynamic Language require 'normal' if something_special(oh_noes) require 'mystery_module' end

Path Searching Hell More Paths More Problems! ["/home/enebo/work/jruby/frogger/lib", "/home/enebo/work/jruby/frogger/vendor", "/home/enebo/work/jruby/frogger/app/channels", "/home/enebo/work/jruby/frogger/app/controllers", "/home/enebo/work/jruby/frogger/app/ controllers/concerns", "/home/enebo/work/jruby/frogger/app/helpers", "/home/enebo/work/jruby/frogger/app/jobs", "/home/enebo/work/jruby/frogger/app/mailers", "/home/enebo/work/jruby/frogger/app/models", "/home/enebo/ work/jruby/frogger/app/models/concerns", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/turbolinks-5.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/webpacker-4.2.2/lib", "/home/enebo/work/jruby/lib/ruby/ gems/shared/gems/actiontext-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/actiontext-6.0.2.1/app/helpers", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/actiontext-6.0.2.1/app/models", "/home/enebo/ work/jruby/lib/ruby/gems/shared/gems/actionmailbox-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/actionmailbox-6.0.2.1/app/controllers", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/ actionmailbox-6.0.2.1/app/jobs", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/actionmailbox-6.0.2.1/app/models", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/actioncable-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ ruby/gems/shared/gems/activestorage-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activestorage-6.0.2.1/app/controllers", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activestorage-6.0.2.1/app/ controllers/concerns", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activestorage-6.0.2.1/app/jobs", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activestorage-6.0.2.1/app/models", "/home/enebo/work/jruby/lib/ ruby/gems/shared/gems/actionview-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/bundler-2.0.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/webdrivers-4.2.0/lib", "/home/enebo/work/jruby/lib/ruby/ gems/shared/gems/web-console-4.0.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/tzinfo-data-1.2019.3/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/turbolinks-source-5.2.0/lib", "/home/enebo/work/jruby/ lib/ruby/gems/shared/gems/selenium-webdriver-3.142.7/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/sass-rails-6.0.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/sassc-rails-2.1.2/lib", "/home/enebo/work/ jruby/lib/ruby/gems/shared/gems/tilt-2.0.10/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/sassc-2.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/extensions/universal-java-13/2.5.0/sassc-2.2.1", "/home/enebo/ work/jruby/lib/ruby/gems/shared/gems/rubyzip-2.1.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/rails-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/sprockets-rails-3.2.1/lib", "/home/enebo/work/ jruby/lib/ruby/gems/shared/gems/sprockets-4.0.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/railties-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/thor-1.0.1/lib", "/home/enebo/work/jruby/lib/ruby/ gems/shared/gems/rack-proxy-0.6.5/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/puma-4.3.1-java/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/method_source-0.9.2/lib", "/home/enebo/work/jruby/lib/ ruby/gems/shared/gems/listen-3.1.5/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/ruby_dep-1.5.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/rb-inotify-0.10.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/ shared/gems/rb-fsevent-0.10.3/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/jbuilder-2.9.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/ffi-1.12.1-java/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/ gems/childprocess-3.0.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/capybara-3.31.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/xpath-3.2.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/ regexp_parser-1.6.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/bindex-0.8.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/extensions/universal-java-13/2.5.0/bindex-0.8.1", "/home/enebo/work/jruby/lib/ruby/ gems/shared/gems/addressable-2.7.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/public_suffix-4.0.3/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activerecord-jdbcsqlite3-adapter-60.1-java/lib", "/home/ enebo/work/jruby/lib/ruby/gems/shared/gems/jdbc-sqlite3-3.28.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activerecord-jdbc-adapter-60.1-java/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/ actionmailer-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/mail-2.7.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/mini_mime-1.0.2/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/ marcel-0.3.3/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/mimemagic-0.3.3/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activerecord-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/ activemodel-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activejob-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/globalid-0.4.2/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/ websocket-driver-0.7.1-java/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/websocket-extensions-0.1.4/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/nio4r-2.5.2-java/lib", "/home/enebo/work/jruby/lib/ruby/ gems/shared/gems/actionpack-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/rack-test-1.1.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/rack-2.1.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/ shared/gems/rails-html-sanitizer-1.3.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/loofah-2.4.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/crass-1.0.6/lib", "/home/enebo/work/jruby/lib/ruby/gems/ shared/gems/rails-dom-testing-2.0.3/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/nokogiri-1.10.7-java/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/erubi-1.9.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/ shared/gems/builder-3.2.4/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/activesupport-6.0.2.1/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/zeitwerk-2.2.2/lib", "/home/enebo/work/jruby/lib/ruby/gems/ shared/gems/tzinfo-1.2.6/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/thread_safe-0.3.6-java/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/minitest-5.14.0/lib", "/home/enebo/work/jruby/lib/ruby/gems/ shared/gems/i18n-1.8.2/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/concurrent-ruby-1.1.5/lib", "/home/enebo/work/jruby/lib/ruby/gems/shared/gems/rake-13.0.1/lib", "/home/enebo/work/jruby/lib/ruby/2.5/site_ruby", "/ home/enebo/work/jruby/lib/ruby/stdlib"]

• Critical code (like Parser) takes time to warmup Everything Starts Cold Java Instructions (java bytecode) interpret C1 compile native code better native code java bytecode interpreter execute C2 compile Java Virtual Machine deoptimize

total execution time (lower is better) 0 0.45 0.9 1.35 1.8 -e 1 CRuby JRuby (JDK8) JRuby (10th iter) JRuby (50th iter)

total execution time (lower is better) 0 1.25 2.5 3.75 5 gem --version gem list (~350 gems) CRuby JRuby (JDK8) JRuby (10th iter)

Other Implementations • CRuby: bytecode compile and interpret • Low peak performance but fastest startup across the board • TruffleRuby: AST interpret + Futamura projection via Graal • Extremely long startup in JVM mode (10x JRuby) • Native compile base startup =~ CRuby • Apps still slow to start (2-3x JRuby)

A History of JRuby Startup

In the beginning… Circa Java 1.4 Ruby (.rb) Lexer Parser interpret interpreter keyword_def,tIDENTIFIER[foo],NL tIDENTIFIER[puts],tSTRING_BEG, tSTRING_CONTENT[hello],tSTRING_END,NL keyword_end,NL tIDENTIFIER[foo],EOF Root Method Call: Foo “foo” Call: Puts “hello” def foo puts "hello" end foo All hail the interpreted AST runtime

AST Runtime • Startup was ok for the time • Ruby was much simpler back then • Quick tasks were ~2-3x slower than C Ruby but very short runs • Peak performance was not good but was better than C Ruby

Lexer Optimization • Serialize lexer stream • Java 1.4 boost was significant (~25% faster) • Java 5 dropped improvement to <5%…death to serialization! Ruby (.rb) Lexer Parser interpret interpreter Ruby (.ser)

AST JIT Added • Helped keep performance edge over C Ruby 1.9 • Quick tasks startup time unaffected • Longer tasks could be if they contained hot code • This startup time of large web applications Ruby (.rb) Lexer Parser interpret interpreter Compiler Called enough To compile

Honorable Mention…Bytecode AOT • AOT all the things to class files! • Class verification on: insanely slow • Class verification off: slower than manually parsing Ruby • More on this technique later…

JRuby adds its own IR • Startup decreased 15-25% on short runs • Even better Steady State performance • Longer app startup potentially improves more Ruby (.rb) Lexer Parser IR Builder Startup Instructions Full Instructions Bytecode Generation Instructions and passes…performance for the masses

Lazy Building of Methods • AST tree smaller than IR build of that tree • Until a method's first call do not build it • Saves memory (%40 of Rails methods not called) • Eliminates build time (15-25%) if not called.

JRuby adds IR Serialization Ruby (.rb) Lexer Parser IR Builder Startup Instructions Full Instructions Bytecode Generation Ruby (.ir) Silver bullet?

IR Serialization • SLOWER THAN PARSING FROM SCRATCH…barely

Add --dev mode • Only use IR startup instructions in interpreter • Disable C2 (-XX:TieredStopAtLevel=1) • Disable bytecode verification • Most significant startup optimization to date

Dev Mode Flag total execution time (lower is better) 0 1.15 2.3 3.45 4.6 gem list (~350 gems) JRuby JRuby --dev

Native Compilers • Generate a JRuby executable • Excelsior JET and jaotc • Very slightly faster than --dev…but not quite enough • There's new developments here...

Startup Experiments • Preboot or reuse JVM process • Lazy deserialize and IR constant pooling • Precompile to JVM bytecode

Pre-booting Options • Nailgun - reuse same JVM repeatedly • Poor resource cleanup for badly-behaved apps • Drip - pre-boot next JVM in background • Troublesome TTY issues, stale instances • CRIU - checkpoint and restore in userspace • Linux only, still in proof-of-concept stage for JVM apps

Lazy Instruction Deserialization • All Scopes (in IR) are needed for implementation reasons • …but startup instructions are only needed it they are used IRScope Flags StaticScope Closures … Instructions Decode on demand

0 0.425 0.85 1.275 1.7 gem list (20 gems) 1.32 1.61 1.41 --dev old serialize + --dev lazy serialize --dev Java 13.0.2+8

0 1.025 2.05 3.075 4.1 gem list (2000 gems) 3.87 4.07 3.91 --dev old serialize + --dev lazy serialize --dev Java 13.0.2+8

0 3.575 7.15 10.725 14.3 rails console 13.7 14 14.3 --dev old serialize + --dev lazy serialize --dev Java 13.0.2+8

Add constant pooling • Serializer encodes/decodes a lot of the same values • Common Symbol Operand type into per IRScope constant pool • Lazily Decode pool when instructions decode • Reduces disk space • Reduces extra lookups

0 0.425 0.85 1.275 1.7 gem list (20 gems) 1.27 1.32 1.61 1.41 --dev old serialize + --dev lazy serialize --dev lazy + pool Java 13.0.2+8

0 1.025 2.05 3.075 4.1 gem list (2000 gems) 3.64 3.87 4.07 3.91 --dev old serialize + --dev lazy serialize --dev lazy + pool Java 13.0.2+8

0 3.575 7.15 10.725 14.3 rails console 13.6 13.7 14 14.3 --dev old serialize + --dev lazy serialize --dev lazy + pool Java 13.0.2+8

JVM Bytecode Compiler • Used for JIT at runtime • 50 call compile threshold • Background compiler threads • Also supports compiling entire scripts • Used for "main" script by default

Precompiling Goals • JVM, JRuby initialization largely unchanged • Read, parse, IR compile, IR interpret eliminated • Reduce JVM classes and IR state on heap • Reduce startup (maybe) and warmup (probably) by skipping JIT

$ jruby -Xjit.logging -S gem -v 2020-01-31T13:44:10.835+01:00 [main] INFO Ruby : done compiling target script: /Users/headius/projec 2020-01-31T13:44:10.981+01:00 [Ruby-0-JIT-1] INFO JITCompiler : block done jitting: Gem::Specificati 2020-01-31T13:44:10.989+01:00 [Ruby-0-JIT-1] INFO JITCompiler : method done jitting: Gem::StubSpecif 2020-01-31T13:44:10.993+01:00 [Ruby-0-JIT-1] INFO JITCompiler : method done jitting: Gem::BasicSpeci 2020-01-31T13:44:10.996+01:00 [Ruby-0-JIT-1] INFO JITCompiler : method done jitting: Gem::BasicSpeci 2020-01-31T13:44:10.998+01:00 [Ruby-0-JIT-1] INFO JITCompiler : block done jitting: Gem::Specificati 2020-01-31T13:44:11.000+01:00 [Ruby-0-JIT-1] INFO JITCompiler : block done jitting: Gem::Specificati $ jruby -Xjit.logging -X+C -S gem -v 2020-01-31T13:44:20.839+01:00 [main] INFO Ruby : done compiling target script: uri:classloader:/jrub 2020-01-31T13:44:20.861+01:00 [main] INFO Ruby : done compiling target script: uri:classloader:/jrub 2020-01-31T13:44:20.919+01:00 [main] INFO Ruby : done compiling target script: uri:classloader:/jrub 2020-01-31T13:44:20.940+01:00 [main] ERROR Ruby : failed to compile target script: uri:classloader:/ 2020-01-31T13:44:20.947+01:00 [main] INFO Ruby : done compiling target script: uri:classloader:/jrub 2020-01-31T13:44:21.008+01:00 [main] INFO Ruby : done compiling target script: file:/Users/headius/p Normal JIT mode Force compile mode

$ jruby -Xcompile.cache.classes -Xcompile.cache.classes.logging -X+C -S gem -v saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/java.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/java/core_ext.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/java/core_ext/module.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/java/java_ext.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/jruby_dot_jar/jruby/jruby.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/kernel.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/process.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/io.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/gc.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/range.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/jruby_dot_jar/jruby/preludes.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/prelude.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/enc_prelude.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/unicode_normalize.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/gem_prelude.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rbconfig.class saved compiled script as /Users/headius/.ir/uri_3a_classloader_3a_/jruby/kernel/rbconfig.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/compatibility.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/defaults.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/errors.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/version.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/requirement.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/platform.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/basic_specification.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/stub_specification.class saved compiled script as /Users/headius/.ir/Users/headius/projects/jruby/lib/ruby/stdlib/rubygems/util/list.class

Does it Work? • rails generate scaffold produces over 1200 class files • Cached size exceeds 80MB • At command line most of this never JITs • JVM interpreter usually slower than our interpreter • Trace bytecode execution to measure improvement

TraceBytecodes • Debug option -XX:+TraceBytecodes • Print out all bytecodes as executed • Use -Xint to also capture bytecodes that JIT • Claes Redestad's bytestacks: https://github.com/cl4es/bytestacks • Looking only at JVM in JIT mode • Need to quantify cold execution

Cold Bytecodes for -e 1 -e 1 -e 1 cached Number of bytecodes executed (cold, in millions) 0 10 20 30 40 JVM JRuby base JRuby libs Other

Cold bytecodes for gem list gem list gem list cached Number of bytecodes executed (cold, in millions) 0 12.5 25 37.5 50 JVM JRuby base RubyGems Other gem list

InvokeDynamic Usage • Normal mode: Ruby literals, constant lookups, global vars • Indy mode: method, block invocations • InvokeDynamic + MethodHandle are expensive in JVM interpreter • LambdaForms never get a chance to optimize • More bytecode than manual lookup + virtual call varargs • Enabling full indy runs 48M cold bytecodes vs 33M for "-e 1"

AOT Mode • AOT mode: No indy at all • A bit more bytecode generated • Only direct method handles (no LambdaForms) • (Constant lookup still using indy, will fix later) • Cold bytecodes reduced vs normal precompile

Cold Bytecodes for -e 1 -e 1 -e 1 cached -e 1 cached2 Number of bytecodes executed (cold, in millions) 0 10 20 30 40 JVM JRuby base JRuby libs Other

Cold bytecodes for gem list gem list gem list cached gem list cached2 Number of bytecodes executed (cold, in millions) 0 12.5 25 37.5 50 JVM JRuby base RubyGems Other gem list

Mix and Match • Experimenting with combinations • Interp, JIT, AOT modes • Serialized IR, precompiled bytecode caches • JVM options • Disabled verification and AppCDS on Hotspot • -Xquickstart and -Xshareclasses on OpenJ9

0 0.45 0.9 1.35 1.8 gem list (20 gems) 1.42 1.71 1.13 1.12 1.41 --dev appcds --dev lazy serialize appcds --dev classcache --dev classcache appcds --dev Java 13.0.2+8

0 1 2 3 4 gem list (2000 gems) 3.84 3.53 3.98 3.42 3.45 3.91 --dev appcds --dev lazy serialize appcds --dev classcache --dev classcache appcds --dev j9 quickstart+shareclasses --dev Java 13.0.2+8

0 4 8 12 16 rails console 11.2 12.5 15.1 12.7 13.5 14.3 --dev appcds --dev lazy serialize appcds --dev classcache --dev classcache appcds --dev partial classcache appcds --dev Java 13.0.2+8

Futures

Native Compilation • Native AOT is cool again • Time to revive GCJ! • We are experimenting with GraalVM native image

total execution time (lower is better) 0 0.75 1.5 2.25 3 -e 1 0.054 2.472 1.268 JRuby --dev TruffleRuby JVM TruffleRuby SVM

total execution time (lower is better) 0 5.5 11 16.5 22 gem --version gem list (~350 gems) JRuby --dev TruffleRuby JVM TruffleRuby SVM

GraalVM Native Image • Compile all of JRuby to native (working POC) • Too many limitations? • No invokedynamic, limited reflection, no dynamic classloading, ... • Ultimate goal: fully native Ruby apps (no startup or warmup) • Good for tools, microservices • Still need JVM for peak performance

total execution time (lower is better) 0 0.45 0.9 1.35 1.8 -e 1 0.117s 0.124s 1.63s 0.1s CRuby JRuby (JDK8) JRuby (10th iter) JRuby native

Native Futures • Compile Ruby app + library sources to native • Needed bytecode AOT to be working • Static optimizations • Remove unneeded parts of JRuby • Probably limited to small services, command line tools

Miniature Ruby subset interpreter • When file uses a restricted subset of Ruby, encode as "special miniature language" • fcalls with literals (e.g. require "date") • module • class • def (their bodies are deserialized like normal and lazy)

Miniature Ruby subset interpreter • More complicated Ruby uses ordinary deserialization path • Implemented a small static method to warm up quick • Will bypass creating IR directly • But IR can be lazily reconstructed

Miniature Ruby subset interpreter require 'date' module Package class FooDriver def run end end class BarDriver def run end end end fcall :require, 'date' create_module :Package create_class :FooDriver create_method :run, @scopeXXX return # goes back to Package create_class :BarDriver create_method :run, @scopeYYY

Summary • Precompiling to bytecode works but sometimes hurts startup • Class sharing features competitive with --dev without JIT limits • Lazier, lighter IR or subset languages show promise • Native compile shows promise but difficult to apply to Ruby

Thank You! • Charles Nutter @headius, Tom Enebo @tom_enebo • https://www.jruby.org • https://github.com/jruby/jruby • Chat with JRuby devs, users • jruby on Matrix • #jruby on Freenode IRC • Mailing list: https://lists.ruby-lang.org