Eclipse OpenJ9 version 0.16 release notes
These release notes support the Eclipse OpenJ9 0.16 release plan.
Binaries and supported environments
OpenJ9 release 0.16 supports OpenJDK 13.
Binaries are available at the AdoptOpenJDK project:
All builds are tested against the OpenJ9 functional verification (FV) test suite, the OpenJDK test suites, and additional tests at AdoptOpenJDK.
To learn more about support for OpenJ9 releases, including OpenJDK levels and platform support, see Supported environments.
Notable changes in this release
The following table covers notable changes in v0.16. Further information about these changes can be found in the user documentation.
| Issue number |
Description |
Version / Platform |
Impact |
| #6271 |
Class data sharing for bootstrap classes is enabled by default |
OpenJDK8 and later |
Class data sharing is enabled by default for bootstrap classes, unless your application is running in a container. You can use the -Xshareclasses option to change the default behavior. |
| #6541 |
New option to share VM anonymous classes in the shared classes cache |
OpenJDK8 and later |
Anonymous classes (defined by Unsafe.defineAnonymousClass) are now stored in the shared classes cache by default so that they are available for ahead-of-time (AOT) compilation. To
prevent these classes being shared, use the -XX:-ShareAnonymousClasses option. |
| #6536, #5480 |
Changes to the shared classes cache generation number |
OpenJDK8 and later |
The format of classes that are stored in the shared classes cache is changed. To save space, all existing shared caches can be removed unless they are in use by an earlier release. For more information about deleting a shared classes cache, see the -Xshareclasses option. |
| #6234 |
Performance improvements for JVMTI watched fields on IBM Power® systems |
OpenJDK8 and later (AIX® and Linux on POWER) |
In earlier releases, performance improvements were introduced for JVMTI watched fields on x86, Linux on Z, and z/OS systems. These
improvements are now available for AIX and Linux on POWER systems. |
| #6713 |
Support for Transparent HugePage allocation by default |
OpenJDK8 and later (Linux on x86) |
In release 0.15, support was introduced for Transparent HugePage on Linux when the madvise (/sys/kernel/mm/transparent_hugepage/enabled) setting is set by specifying the -XX:+TransparentHugePage option on the command line. This support is now enabled by default for Linux on x86 systems. |
| #5164 |
New jcmd tool |
OpenJDK8 and later |
For compatibility, OpenJ9 includes an independent implementation of the jcmd tool, which can run diagnostic commands on a specified VM or VMs. |
| #3743 |
Automatically setting an initial heap size by default |
OpenJDK8 and later |
In release 0.15, a new feature was introduced that allowed OpenJ9 to learn and set an appropriate initial heap size for an application as an alternative to a user manually sizing and setting an -Xms value. This feature could be enabled by setting the -XX:+UseGCStartupHints option on the command line. This
option is now enabled by default. |
| #5822 |
Options -Xverify:none and -noverify are deprecated |
OpenJDK13 and later |
The -Xverify:none and -noverify options are deprecated in Java 13 and might be removed in a future release. A warning message is issued when these commands are used. |
Known Issues
The v0.16 release contains the following known issues and limitations:
| Issue number |
Description |
Platform |
Impact |
Workaround |
| #2507 |
Restriction analyzing system (core) dumps |
Linux and Windows |
You must use a 32-bit JVM to look at a 32-bit core, and a 64-bit JVM to look at a 64-bit core. This restriction will be fixed in a later version of OpenJ9. |
None |
| #479 |
Non-compressed references VM builds not available |
AIX, Linux on Z, Linux on Power |
Non-compressed references VM builds, which support heaps larger than 57GB, are built on Linux on x86, Windows, and macOS. |
Manual builds on other platforms are possible by following our detailed build instructions. |
| #897 |
Javadoc not building some OpenJ9 extensions. |
All platforms |
Some API documentation is missing in the build/<platform>/docs directory. |
None |
| #898 |
Javadoc building some unsupported OpenJ9 extensions. |
All platforms |
Some API documentation in build/<platform>/docs is not supported with OpenJ9. |
None |
Other changes
A full commit history for this release is available at Eclipse OpenJ9 v0.16.0.
