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What's new in version 0.46.0

The following new features and notable changes since version 0.45.0 are included in this release:

Features and changes

Binaries and supported environments

Eclipse OpenJ9™ release 0.46.0 supports OpenJDK 8, 11, 17, 21, and 22.

CentOS 6, CentOS 7, Red Hat Enterprise Linux (RHEL) 6, and RHEL 7 are removed from the list of supported platforms.

RHEL 8.6 and 9.0 are out of support. RHEL 8.8 and 9.2 are the new minimum operating system levels.

To learn more about support for OpenJ9 releases, including OpenJDK levels and platform support, see Supported environments.

MD5 message digest algorithm support for OpenSSL

OpenSSL native cryptographic support is added for the MD5 message digest algorithm, providing improved cryptographic performance. OpenSSL support is enabled by default. If you want to turn off support for the MD5 message digest algorithm, set the -Djdk.nativeDigest system property to false.

Support added for the com.sun.management.ThreadMXBean.getTotalThreadAllocatedBytes() API

With this release, the OpenJ9 VM implementation supports measurement of the total memory allocation for all threads (com.sun.management.ThreadMXBean.getTotalThreadAllocatedBytes() API).

The getTotalThreadAllocatedBytes() method now returns the total thread allocated bytes instead of -1.

The JITServer AOT caching feature enabled by default at the JITServer server

-XX:+JITServerUseAOTCache is the default setting at the JITServer server now. That means that you don't have to specify the -XX:+JITServerUseAOTCache option at the server to enable the JITServer AOT caching feature.

Although this option is by default enabled at the server, it is still disabled for the JITServer clients. The clients that want to use the JITServer AOT caching, must still specify the -XX:+JITServerUseAOTCache option on the command line. Also, now the clients don't have to enable the shared classes cache feature to use the -XX:+JITServerUseAOTCache option.

For more information, see -XX:[+|-]JITServerUseAOTCache.

The extended Hot Code Replace (HCR) capability disabled and -XX:[+|-]EnableExtendedHCR option added

By default, the extended HCR capability in the VM is disabled for all OpenJDK versions, which is a change from the previous releases. You can enable the HCR capability by using the new option, -XX:+EnableExtendedHCR option.

The extended HCR feature is deprecated in this release and will be removed in a future release. From OpenJDK 25 onwards, extended HCR will not be supported. Following that, the extended HCR support will be removed from other earlier OpenJDK versions also.

New system property added to improve jcmd attaching in case of the SocketException error on Windows platform

When the jcmd tool sends a command to a running VM, the command might throw the Socket Exception error on Windows platform. Instead of failing the attaching request, you can specify the number of times the tool retries attaching to the target VM with the new system property, -Dcom.ibm.tools.attach.retry.

-Xtgc:allocation report includes core allocation cache statistics per thread

The -Xtgc:allocation option prints thread-specific allocation cache (TLH) statistics in addition to the cumulative allocation statistics.

New -XX:[+|-]ShareOrphans option added

When -Xshareclasses was specified, only those class loaders that implemented the OpenJ9's public shared classes cache APIs (and its child class loaders) could store classes to the shared classes cache. Custom class loaders that did not implement these cache APIs cannot pass the module or class path information to the VM. Classes of such class loaders were not stored to the cache.

You can enable class sharing from all class loaders, irrespective of whether the class loader implements the shared classes cache API, with the -XX:+ShareOrphans option.

For more information, see -XX:[+|-]ShareOrphans.

New -XX:[+|-]JITServerAOTCacheIgnoreLocalSCC option added

From this release onwards, the default behavior of the client when it uses the JITServer AOT cache is to bypass its local shared classes cache (if one is set up) during JITServer AOT cache compilations. You can control how the JITServer AOT cache feature interacts with the local cache at JITServer client VMs with the -XX:[+|-]JITServerAOTCacheIgnoreLocalSCC option.

Java 11 (LTS) and later New -XdynamicHeapAdjustment option added

By default, if a checkpoint is taken in a container with no memory limits and then restored in a container with memory limits, the restored VM instance does not detect the memory limits.

You can now create a single image file and restore it on various nodes with different memory limits. The new option -XdynamicHeapAdjustment automatically adjusts the maximum Java heap size (-Xmx) and minimum Java heap size (-Xms) values such that they are within the physical memory limitations on the system. End of content that applies only to Java 11 and later

Known problems and full release information

To see known problems and a complete list of changes between Eclipse OpenJ9 v0.45.0 and v0.46.0 releases, see the Release notes.