Resource: LCE13 Name: LEG - OpenJDK Date: 10-07-2013 Speaker: Andy Johnson Video: https://www.youtube.com/watch?v=_mjNleD48Cc&feature=c4-overview&list=UUIVqQKxCyQLJS6xvSmfndLA

1. Group photograph at Linaro Connect in Copenhagen
Monday 29 Oct 2012
Why? What? How? Who? Where? When?
LCE-13
OpenJDK

2. www.linaro.org
Meet the team
• RedHat
o Andrew Haley (Template Interpreter & C1 Compiler)
o Andrew Dinn (C2 Compiler)
• Linaro
o Andrew Johnson (Test and Benchmarking)
o Ed Nevill (General dogsbody)
• With thanks to
o Riku Voipio (help with OpenEmbedded)
o Andrew McDermott (help with CI loop integration)
• Management
o Andrea Gallo (LEG Director)
o Ilias Biris (Project Manager)

3. www.linaro.org
Why Java
• Java is the most popular programming language!
– Or maybe 2nd most popular
– Depending who you talk to
• Java is used in servers – a lot
• Tends to be used in performance critical database apps.
• Tier 1 Java support is a requirement
Why Java

4. www.linaro.org
Java terminology
• J2ME – Java 2 Micro Edition
– Opensource implementation by phoneMe
• J2SE – Java 2 Standard Edition
– Opensource implementation by OpenJDK
• J2EE – Java 2 Enterprise Edition
– OpenJDK + Jboss
• OpenJDK
– Hotspot – The VM
– JDK – The Java runtime
– Other components (corba, jaxp, jaxws, nashorn)

5. www.linaro.org
Inside Hotspot
• Zero
– C++ bytecode interpreter – veerrrryy sloooowww
– Useful as a reference implementation only
• Template Interpreter
– Chunk of assembler (template) for each bytecode
– Templates copied and modified depending on entry
conditions (atos, itos, vtos, dtos)
– Computed goto at end of each loop removes loop
overhead.
– Performance improvement 3-5x over Zero

6. www.linaro.org
Inside Hotspot
• C1 (Client) Compiler
– Simple register allocator
– Simple straight line compilation
– Simple optimisation across bytecodes
– Assumed 32 bit!
– Performance ~10 x Template interpreter
• C2 (Server) Compiler
– Aggressive global optimisation
– Predictive optimisation / deoptimisation
– Performance ~2 X C1

7. www.linaro.org
Inside Hotspot
• Tiered compilation
– Start executing in Template interpreter
– Compile with C1 if method is hot
– Compile with C2 if method is still hot
– Tiered compilation good for dynamically changing loads
– If load is static, may as well just use C2
– But C2 will give very slow startup,

8. www.linaro.org
Current Status
• AARCH64 initial released pushed Monday
– Announcement on aarch64 mailing list
• Template Interpreter
– Code complete
– Fails 2 more Mauve tests compared to Zero
– “Pretty Rock Solid”
• C1 Compiler
– Compiling 100s of methods
– Not quite code complete – nearly
• C2 Compiler
– Work in progress

9. www.linaro.org
Next Steps
• Template Interpreter
– Continue testing with JTReg & fix faults
– Integrate build into OE & develop CI loop
• C1 Compiler
– Fix existing faults to get to code complete
– Once code complete move to testing
– Not yet stable enough to test
• C2 Compiler
– Under development adinn @ redhat

10. www.linaro.org
Resources
• Source mercurial
– http://hg.openjdk.java.net/aarch64-port/jdk8
• Mailing list
– aarch64-port-dev@openjdk.java.net
• IRC
– Server: irc.oftc.net Channel: #openjdk

11. Group photograph at Linaro Connect in Copenhagen
Monday 29 Oct 2012
Test and Benchmark Status
LCE-13
OpenJDK

12. www.linaro.org
Available Validation Tests
● Mauve
○ Developed for "clean room" implementations of Java
○ Maintained through Java 6
○ Uses a Java test harness
■ Tests can be run on the same Java that runs the harness or a
designated JVM
■ Over 5000 tests, covering both java and javax packages
○ Tests run on several ports
■ OpenJDK 7 Zero port
■ OpenJDK 8 Zero port
■ OpenJDK 8 Template interpreter
■ OpenJDK 8 Client compiler (C1)
● JTREG
○ Unit tests supplied with OpenJDK
○ Current with OpenJDK
○ Over 3000 tests in combined "core" and "default" suites
○ Same harness used to run JCK when available

13. www.linaro.org
Test Results
OpenJDK 7 x86-64 aarch64 Zero
Mauve Fail Total Tests Fail Total Tests
Totals 773 5267 800 5261
OpenJDK8 x86-64
Zero
aarch64
Zero
aarch64
Template
aarch64
Client
Mauve Fail Total Fail Total Fail Total Fail Total
Totals 554 5119 752 5114 570 5112 581 5112
OpenJDK 8 x86-64
Zero
aarch64
Zero
aarch64
Template
JTREG Pass Fail Pass Fail Pass Fail
Totals 2957 78 2638 381 2638 381

14. www.linaro.org
Benchmarks
● Embedded Caffeinemark
○ Developed for Java ME
○ Small enough to run on emulator
● SPECjvm2008
○ Freely available
○ Single subset run on emulator as proof of concept
○ More complete runs when hardware available
● SPECjbb2013
○ Newly released
○ Designed specifically for Java server performance
○ Available under license - will obtain when all components are
ready