Jikes RVM

Project Status

General project status

Jikes RVM lacks support for anything later than Java 1.6 and the project sees little development at the moment.

Note: The information on this page refers to the status in the code repository and not to the status in the current release.

Note: If you want to help, please see How to Help or inquire via the mailing lists.

Important project goals

• Add support for the OpenJDK class libraries (a prerequisite for adding support for newer Java versions)
• Improve compliance with JVM spec, particularly with the Java Memory Model

Additional project goals in no particular order

• Improve Intel 64-bit support (see below for detailed status)
• Merge relevant changes from MRP
• Improve and extend test suites
• Improve stability
• Write unit tests for all classes
• Add support for relevant new platforms (ARM?)

Detailed project status

This section provides more detailed project status information for the components. If you think an important point is missing here, please contact us via the mailing lists.

Benchmarks

• DaCapo 2006-MR-2 runs on Jikes RVM
• Some benchmarks of DaCapo 9.12 work
• Parts of SPECjvm2008 work (see RVM-484)

Community

• Core team consists wholly of volunteers: no paid developers
• Jikes RVM is currently not packaged for any major distribution

Memory Management

• Generational Immix (the default collector) is stable
• The other collectors are reasonably stable but have some bugs (as shown by the regression tests)
• The MarkCompact collector is currently too buggy to use
• Notable omissions in the collector choices include Baker-style collectors, the Compressor and on-the-fly collectors. Note: There is an implementation of the Sapphire garbage collector for Jikes RVM but as far as we know there’s currently nobody working on getting the code into the mainline.
• MMTk currently doesn’t deal correctly with page sizes

OpenJDK

• work happens on the master branch
• bootimage builds
• prototype can run some tests from the basic test run
• TODOs: make unit tests run, fix opt builds, make pre-commit test run pass

x64 support

• regression tests on x64 configurations run reasonably well with the notable exception of SPECjbb2005
• x64 is the default (the latest release still has 32-bit as default)

Runtime

• The runtime is reasonably modular but it doesn’t make very good use of interfaces
• Jikes RVM currently does not follow the JVM specification
• Several features normally found in commercial JVMs are not implemented: strictfp and JVMTI are currently unsupported. There is partial support for JMX with GNU Classpath.

Adaptive Optimization System

• The AOS provides a good level of control via compiler replay
• The AOS provides clear extension points
• Jikes RVM currently uses only one compilation thread at runtime and the current AOS model does not support multiple compilation threads
• The provided AOS models do not support Feedback-Directed Optimizations

Compilers

• SSA form is disabled. Scalar SSA form may be fixable; Heap SSA form is considered too broken
• Many optimizations are disabled because they rely on SSA or are considered too buggy
• Some standard optimizations are missing, e.g. Global Array Bound check elimination
• Java Memory Model (JMM) is not correctly implemented
• Bootimage compilation is single-threaded by default because it is too unrealiable with multiple threads

Infrastructure

• Regression tests are run regulary for ia32, x64 and ppc64 and reports are sent to the regressions mailing list
• Core team members have access to a Jenkins server to view test results in detail
• More regression machines would be useful, in particular PowerPC machines that can be accessed by all team members
• Currently no code review tools in use
• Some unit tests (via JUnit) exist but most classes don’t have unit tests