Presentation on the Graal VM at BG OUG (http://www.bgoug.org/) summer conference, 3-5June, 2016, Borovetz, Bulgaria

1. JVM++: The Graal VM
Martin Toshev,
BGOUG, 04.06.2016

2. Special thanks to Thomas Wuerthinger and
Oracle Labs for inspiring this presentation …

3. Who am I
Software consultant (CoffeeCupConsulting)
BG JUG board member (http://jug.bg)
OpenJDK and Oracle RDBMS enthusiast

4. Who am I
Author of Learning RabbitMQ

5. Agenda
• Overview of the Graal VM
• Building and managing Graal
• Performance benchmarks
• Future directions

6. Overview of the Graal VM

7. Overview of the Graal VM
Some background …
static compilation vs dynamic compilation
static compiler
source code (e.g. JVM bytecode)
dynamic compiler
runtime
machine code
runtime
source code (e.g. JVM bytecode)
machine code

8. Overview of the Graal VM
• The javac tool performs static compilation of Java
sources to bytecode
• The JVM may perform dynamic compilation of
bytecode to machine code for optimization using a
JIT (Just-in-Time) compiler

9. Overview of the Graal VM
• Graal is a new JIT (Just-in-Time) compiler for the
JVM
• Brings the performance of Java to scripting
languages (via the Truffle API)
• written in Java

10. Overview of the Graal VM
• In essence the Graal JIT compiler generates
machine code from an optimized AST rather than
bytecode
• However the Graal VM has both AST and bytecode
interpreters

11. Overview of the Graal VM
• The Graal VM supports the following types of
compilers (apart from the Graal JIT compiler):
--vm server-nograal // server compiler
--vm server // server compiler using Graal
--vm graal // Graal compiler using Graal
--vm client-nograal // client compiler
--vm client // client compiler running Graal

12. Overview of the Graal VM
• The Truffle API:
– is a Java API
– provides AST (Abstract Syntax Tree) representation of
source code
– provides a mechanism to convert the generated AST
into a Graal IR (intermediate representation)

13. Overview of the Graal VM
• The Truffle API is declarative (uses Java
annotations)
• The AST graph generated by Truffle is a mixture of
control flow and data flow graph
• Essential feature of the Truffle API is the ability to
specify node specializations used in node rewriting

14. Overview of the Graal VM
• The Truffle API is used in conjunction with custom
annotation processor that generates code based
on the Truffle annotations used in the interpreter
classes
Truffle
Interpreter
javac
Annotation
processor
Compiled
Interpreter
Generated
Interpreter
source code

15. Overview of the Graal VM
• General architecture:
HotSpot VM (C++)
Graal (Java)
Truffle (Java) Java Other JVM language
JavaScript Ruby R
Other interpreted
language
Graal <–> Hotspot adapter (C++, Java)
Maxine VM (Java)
Graal <–> Maxine
adapter (Java)

16. Overview of the Graal VM
• Let’s see, for example, how a JavaScript interpreter
works in Graal …

17. Overview of the Graal VM
HotSpot VM (C++)
Graal (Java)
Truffle (Java) Java Other JVM language
JavaScript Ruby R
Other interpreted
language
Graal <–> Hotspot adapter (C++, Java)
Run JavaScript file: app.js

18. Overview of the Graal VM
HotSpot VM (C++)
Graal (Java)
Truffle (Java) Java Other JVM language
JavaScript Ruby R
Other interpreted
language
Graal <–> Hotspot adapter (C++, Java)
JavaScript Interpreter parses app.js and converts it to Truffle AST

19. Overview of the Graal VM
HotSpot VM (C++)
Graal (Java)
Truffle (Java) Java Other JVM language
JavaScript Ruby R
Other interpreted
language
Graal <–> Hotspot adapter (C++, Java)
The app.js Truffle AST is converted to Graal IR (AST)

20. Overview of the Graal VM
HotSpot VM (C++)
Graal (Java)
Truffle (Java) Java Other JVM language
JavaScript Ruby R
Other interpreted
language
Graal <–> Hotspot adapter (C++, Java)
The Graal VM has bytecode and AST interpreters along with a JIT compiler
(optimizations and AST lowering is performed to generate machine code
and perform partial evaluation)

21. Overview of the Graal VM
HotSpot VM (C++)
Graal (Java)
Truffle (Java) Java Other JVM language
JavaScript Ruby R
Other interpreted
language
Graal <–> Hotspot adapter (C++, Java)
When parts of app.js are compiled to machine code by the Graal compiler
the compiled code is transferred to Hotspot for execution by means of
Hotspot APIs and with the help of a Graal – Hotspot adapter interface

22. Overview of the Graal VM
HotSpot VM (C++)
Graal (Java)
Truffle (Java) Java Other JVM language
JavaScript Ruby R
Other interpreted
language
Graal <–> Hotspot adapter (C++, Java)
Compiled code can also be deoptimized and control is transferred back to
the interpreter (e.g. when an exception occurs, an assumption fails or a
guard is reached)

23. Overview of the Graal VM
• Optimizations done on the Graal IR include:
– method inlining
– partial escape analysis
– inline caching
– constant folding
– arithmetic optimizations and others …

24. Overview of the Graal VM
• Currently supported languages include:
– JavaScript (Graal.JS)
– R (FastR)
– Ruby (RubyTruffle)
– Experimental interpreters for C, Python, Smalltalk, LLVM
IR and others …
(some are not open-sourced as of the time of this presentation)

25. Overview of the Graal VM
• The SimpleLanguage project provides a showcase
on how to use the Truffle APIs
Source file Parser Truffle AST Graal VM

26. Building the Graal VM

27. Building the Graal VM
• The Graal VM interoperates with JEP 243: Java-
Level JVM Compiler Interface
• In that regard two modes of operation are
supported – via the Graal VM or via the JVMCI
(JVM Compiler Interface)

28. Building the Graal VM
• Early access builds of Graal available for download
• You can build Graal on any supported platform
(Windows, Linux, MacOS, Solaris) from source
code

29. Building the Graal VM
git clone https://github.com/graalvm/mx.git
export PATH=$PWD/mx:$PATH
git clone https://github.com/graalvm/graal-core.git
cd graal-core
mx --vm graal build
mx vm

30. Building the Graal VM
• The MX tool is a Python (2.7) tool that manages the
Graal projects and allows to:
- update sources and run JUnit tests and benchmarks;
- builds (sub)projects (Java and C++ sources can be built
separately);
- runs VM tools (such as IGV or c1visualizer) that can aid
development of Graal or language interpreters;
- can be used to generate IDE project files for Graal development
(support for Eclipse and NetBeans)

31. The Graal VM
demo

32. Performance benchmarks

33. Performance benchmarks
• According to various JVM benchmarks such as SPECjvm2008
and Scala Dacapo the Graal compiler positions between the
client and server JVM compilers
(source: One VM to Rule Them All, Thomas Wuertinger)
• In general Truffle interpreters provide much better
performance for some dynamic languages

34. Performance benchmarks
• Graal.JS – shows improvement of 1.5x in some cases
with a peak of 2.6x compared to V8 (running Google Octane’s
benchmark)
• RubyTruffle – shows improvements between 1.5x and 4.5x in some
cases with a peak of 14x compared to JRuby
• FastR - shows improvements between 2x and 39x in some cases
with a peak of 94x compared to GnuR
(source: One VM to Rule Them All, Thomas Wuertinger)

35. Future directions

36. Future directions
• Graal provides an extensible framework for
researching and experimenting with other
compiler optimizations
• In that regard new types of compiler optimization
may be introduced in the VM that address runtime
behavior in certain scenarios

37. Future directions
• Graal provides an extensible framework for
creating language interpreters further simplified by
the Truffle API
• In that regard more languages can be introduced
that run in the Graal VM
• Currently existing languages that compile to
bytecode may support Truffle in the future

38. Future directions
• Graal provides an extensible framework for
different types of operating systems and CPU
architectures
• In that regard CPU architectures and operating
systems might be supported by Graal

39. Thank you !
Q&A

40. References
Graal Project
http://openjdk.java.net/projects/graal/
Graal - A New Just In Time Compiler for the JVM
http://www.oracle.com/technetwork/oracle-labs/program-
languages/overview/index.html
Graal VM: GitHub repositories
https://github.com/graalvm

41. References
Graal - A Bytecode Agnostic Compiler for the JVM, Thomas Wuerthinger, JVM
Language Summit
http://medianetwork.oracle.com/video/player/1113230360001
Graal and Truffle: One VM to Rule Them All
http://www.slideshare.net/ThomasWuerthinger/graal-truffle-
ethdec2013?qid=848a4965-9768-40d5-b167-
ccd8eb7d1659&v=&b=&from_search=2

42. References
Graal and Truffle: Modularity and Separation of Concerns as Cornerstones for
Building a Multipurpose Runtime
http://www.slideshare.net/ThomasWuerthinger/2014-0424-graal-
modularity?qid=0e86ed21-0b8f-4087-9212-
68f76546d674&v=&b=&from_search=4
Dynamic Compilation - Thomas Wuerthinger
https://www.youtube.com/watch?v=RLsG2kE1EMI
https://www.youtube.com/watch?v=U_QpToYLsO0
JVMLS 2012: Graal
http://medianetwork.oracle.com/video/player/1785432492001

43. References
Graal Tutorial at CGO 2015 by Christian Wimmer
http://lafo.ssw.uni-linz.ac.at/papers/2015_CGO_Graal.pdf
Writing a language in Truffle: Part 1 - Using Truffle and Graal
https://cesquivias.github.io/blog/2014/10/13/writing-a-language-in-truffle-
part-1-a-simple-slow-interpreter/
Writing a language in Truffle: Part 2 - Using Truffle and Graal
http://cesquivias.github.io/blog/2014/12/02/writing-a-language-in-truffle-
part-2-using-truffle-and-graal/

44. References
Graal publications, JKU, Linz
http://ssw.jku.at/Research/Projects/JVM/Graal.html
Truffle publications, JKU, Linz
http://ssw.jku.at/Research/Projects/JVM/Truffle.html

45. References
R as a citizen in a Polyglot world: The promise of the Truffle framework
http://user2015.math.aau.dk/presentations/112.pdf
Truffle/C Interpreter
http://www.manuelrigger.at/downloads/trufflec_thesis.pdf
Graal.JS - high-performance JavaScript on the JVM talk by Christian Wirth
https://www.youtube.com/watch?v=OUo3BFMwQFo