Release Notes of Azul Zing Stream and Stable Builds of OpenJDK

Zing 25.06.0.0 introduces a new command line option, -XX:AvoidInterruptsDuringHeapFunding, which switches Java heap funding to use system calls that do not get interrupted by signals. This option is disabled by default.

Zing 25.06.0.0 implements optimizations for JNI handle lookups, allowing weak and global JNI handle lookups to be done much quicker.

July 2025 CPU release security fixes.

There are no resolved issues associated with this release.

July 2025 CPU release security fixes.

There are no resolved issues associated with this release.

January 2025 CPU release security fixes.

There are no new issues to report in this release.

There are no resolved issues associated with this release.

Zing 25.05.0.0 implements an additional parameter to the Xlog command line option when you are using unified logging, savecount. You can use this parameter to preserve the starting logs during log rotation, for example:

-Xlog:gc:gc.log::filecount=5,filesize=20M,savecount=1

Note that this parameter only works with unified logging. If you have unified logging disabled, you can still achieve the same result using the command line option -XX:StartupGCLogSaveCount=<number of save counts>.

Zing 25.05.0.0 introduces two new command line options which modify the behavior of code cache flushing:

These new options apply to both -XX:+UseEmergencyCodeCacheFlushing, which is default, and -XX:+UseIncrementalCodeCacheFlushing, which is non-default. When -XX:+UseIncrementalCodeCacheFlushing is enabled, the older flags EnableC1Flushing and EnableTier2Flushing control which code blobs are flushed as long as code cache is below the "high" threshold. The new flags control code caching behaviour after the "high" threshold is crossed.

The size of Zing installer and the installation on disc were reduced by removing files from the directory product/etc/connected-compiler/bin (lib).

April 2025 PSU release security fixes.

Zing 25.04.0.0 changes the default values for the following command line options:

Zing 25.04.0.0 introduces three new command line options:

April 2025 CPU release security fixes.

The unified compiler feature is now turned on by default, allowing for unified local and remote compilation. You can disable this feature and fall back to the local Falcon compiler using the command line option -XX:-UseUnifiedCompilerFrontend.

Zing 25.03.0.0 includes a backport of the OpenJDK command line option -XX:+ PrintExtendedThreadInfo. This option prints additional information in thread dumps. This option is disabled by default.

There are no new issues to report in this release.

Zing 25.02.0.0 changes the way C1 profiling is performed, improving warmup in most cases. With this change, C1 type profiling is disabled for ReadyNow-matched compiles that are already assigned a profile, reducing compiler overhead during warmup.

Zing 25.02.0.0 improves Multi Tiering implementation to further reduce warmup time. For more information about Multi Tiering, see our documentation on Using Multiple Compiler Tiers

Zing 25.02.0.0 implements a new optimization which improves the throughput of your JVM application by eliminating cost of the Garbage Collector (GC) barrier instructions when the GC is not running. The optimization comes with the cost of increase in GC CPU usage while the GC is running, so is best suited for cases where the GC time percentage is already low.

This mode is disabled by default and can be enabled by specifying the command line option -XX:GPGCLvbCodeVersioningMode. You can find more information about this option on the Command Line Options page and more on Hybrid Mode and LVB Code Versioning on the C4 Garbage Collector page.

Zing 25.02.0.0 introduces a new command line option, -XX:+UseTaggedAddressForJavaHeap, which enables the “tagged address for java heap” feature for modern ARM64 systems. This feature provides better out-of-the-box performance and improved memory reporting when you are running Zing in non-ZST mode.

GC logs include a new line in the header, Use address tag bits, which indicates if this feature is enabled or disabled.

This feature is compatible with systems using ARMv8 system architecture or higher and Linux kernel versions 5.4 or higher.

This feature is disabled by default. You can enable it using -XX:+UseTaggedAddressForJavaHeap.

You can now use the command update-alternatives to switch between Zing versions when you have multiple versions of Java installed on your system. For more information, see Get Started with Azul Platform Prime on APT Systems, Switching Between Zing Installations.

A new option, -XX:+UseUnifiedCompilerFrontend has been introduced which allows CNC and Falcon to share the same frontend, enabling the CNC UnifiedCompiler directly in the VM. This option is disabled by default.

January 2025 PSU release security fixes.

Time to safepoint issues and allocation latencies when using UseTaggedAddressForJavaHeap option with large java heaps and large allocation rates.

Zing 25.01.0.0 includes the General Availability (GA) release of JDK 23.

OpenJDK 23 is a Mid-Term Supported (MTS) release. This new OpenJDK version includes several thousand general bug and performance fixes over Java 21 as well as three distinct new features.

You can check out the community podcast where you can learn more about OpenJDK 23 and the evolution process of the OpenJDK project.

There are no new issues to report in this release.

Zing 24.12.0.0 includes the EA (beta) release of OpenJDK 23.

OpenJDK 23 is a Mid Term Supported (MTS) release. This new OpenJDK version includes several thousand general bug and performance fixes over Java 21 as well as three distinct new features.

You can check out the community podcast where you can learn more about OpenJDK 23 and the evolution process of the OpenJDK project.

Zing 24.12.0.0 enhances the garbage collection implementation to process JNI weak references in parallel. This reduces GC durations for applications that use a large number of such references.

Two new fields, _number_of_classes and _number_of_unloaded_classes were added to the main GC log line, which track the total number of classes loaded and unloaded respectively

The install directory for x86_64 DEB packages changed to /usr/lib/jvm/<ZVM directory name>. For example: /usr/lib/jvm/zing-jdk11.0.24.0.101-24.10.0.0-4-amd64.

Support for .jinfo files has been added to manage update-java-alternatives on Debian-based systems with the DEB installers.

There are no new issues to report in this release.

Zing 24.10.0.0 features an update to JVMTI behavior in order to bring it to the modern standard. Previously, a few commercial Java application performance monitoring tools have been reporting too long GC pause times because Zing was reporting non-pausing concurrent GC durations wrongly as GC pauses over JVMTI events JVMTI_EVENT_GARBAGE_COLLECTION_START (GarbageCollectionStart) and JVMTI_EVENT_GARBAGE_COLLECTION_FINISH (GarbageCollectionFinish).

The new correct reporting may increase the actual GC pauses slightly if monitoring software attached with -javaagent using JVMTI is active.

Zing 24.10.0.0 enables the previously implemented command line option OptimizeIdentityHashForDistribution by default. This option implements an optimization to the distribution of identity hash codes. Enabling this option optimizes the protocol for distributing hash codes. Otherwise, some hash table implementations are prone to an unreasonable number of collisions.

The version of libstdc++ packaged with Zing has been upgraded from libstdc++.so.6.0.24 to libstdc++.so.6.0.32.

October 2024 CPU and PSU release security fixes.

There are no new issues to report in this release.

Zing 24.09.0.0 increases the maximum code cache supported from 1758 MB to 4 GB. You can now set both ReservedCodeCacheSize and InitialCodeCacheSize to a value up to 4 GB.

In case you need to disable Extended Native Memory Tracking (NMT), Zing 24.09.0.0 includes new command line option UseExtendedNMT, which you can use to disable Zing’s Extended NMT, and EnableNMTIntegrityChecks, which you can use to disable checks on allocations. Zing runs in Extended NMT mode and includes integrity checks by default. Using -XX:-UseExtendedNMT tells Zing to run NMT in a Zulu-like mode. We do not recommend disabling Extended NMT except in very specific cases.

There are no new issues to report in this release.

The command line option ProfileLogName has been deprecated and replaced with ProfileName. ProfileName supports all existing macros available for ProfileLogName, see Substitution Macros in the Optimizer Hub documentation for more info. It is still possible to use ProfileLogName, however, we recommend that you update your configuration in order to guarantee that you have access to all of the latest features implemented in ProfileName.

Note that using ProfileName overrides ProfileLogName, ProfileLogIn, and ProfileLogOut.

Zing 24.08.0.0 introduces a new feature to the Falcon compiler called Multi-Tiering. Multi-Tiering allows Falcon to schedule methods for compilation under different optimization levels, based on method hotness.

Multi-Tiering assigns hot and active methods to final-tier compilation and cold or inactive methods to mid-tier compilation. Final-tier uses the default Falcon optimization level (usually Falcon optimization level 2) while Mid-tier uses Falcon optimization level 0.

Enable Multi-Tiering using the command line option -XX:+UseMultiTiering.

For more information on Multi-Tiering, see Analyzing and Tuning Warm-Up, Using Multiple Compiler Tiers

Zing 24.08.0.0 raises the maximum java heap size (Xmx) supported with non-ZST mode to 14000 GB (14 TB) on Intel Ice Lake and newer x86 processors when 5-level paging (LA57) is enabled at the OS level.

Zing 24.08.0.0 handles requests for PrintJNI without safepoint pause, allowing PrintJNI to run concurrently with your VM process.

July 2024 PSU release security fixes.

There are no new issues to report in this release.

Zing 24.07.0.0 implements an intrinsification of the method java.lang.reflect.Array.get, leading to a significant performance improvement in some cases.

The logic around InlineTree has been greatly improved. This change allows the decisions reached by inlining to be reconstructed on request, instead of running through the tree with each query which sometimes leads to bloated recursive inlinings.

The MXBean PersistentProfileMXBean has been extended with getReadyNowTier1CompilesRate() and getReadyNowTier2CompilesRate(). These methods allow you to see what percentage of compiles are happening in ReadyNow, when compared to all compiles including non-ReadyNow.

July 2024 CPU release security fixes.

There are no new issues to report in this release.

Several methods have been added to Zing MXBean extensions which can request several metrics from a running JVM. The following methods have been added to Zing MXBeans:

CompilationMXBean can return the total number of enqueued and in-progress compilations, and can return the total number of tier 1 and tier 2 compilations at the time of request.

PersistentProfileMXBean can return the ratio of matched or unmatched classes to the number of classes loaded in the VM at the time of request.

You can find a general overview of Zing MXBeans in the Zing MXBeans documentation, or a complete description of all Zing MXBeans methods in the Zing MXBeans API documentation or in the Javadocs included in the Zing documentation bundle found on the Zing customer downloads page.

GC Log Analyzer’s summary page now includes the ID of the current run from Ready Now Orchestrator, listed as Current VM ID.

GC Log Analyzer’s info page now includes the container OS along with the node OS.

Azul Zing 24.06.0.0 includes a significant improvement to Zing’s crash handler which allows it to properly generate diagnostic data when Falcon threads reach stack memory failure.

There are no new issues to report in this release.

April 2024 PSU release security fixes.

The default value of -XX:ProfileStartupLimitInSeconds has changed from 60 to 0. This follows from a previous change where 0 was changed from "infinite" to actually 0 seconds. For more information on ProfileStartupLimitInSeconds, see Command Line Options, Advanced Miscellaneous Options.

Azul Zing 24.05.0.0 implements some behavioral changes to the command line option VMFootprintLevel. In order to reduce memory footprint, malloc arenas now use half the number of CPU cores when setting a non-default value of VMFootprintLevel; L, M, or S

The minimum value supported for Xms (initial heap size) was lowered drastically from 512 MB to 128 MB. Previously, the minimum supported Xms was 512 MB. The minimum supported Xmx (maximum heap size) remains unchanged at 512 MB. The purpose of this change is to reduce memory consumption from small utility processes which don’t require a high amount of memory.

Azul Zing 24.05.0.0 introduces a new command line option, -XX:ThpDisable, which can be used to disable Transparent Huge Pages (THP) in the entire JVM process, even when system THP settings are enabled. When -XX:+ThpDisable is set, THP is turned off, overriding the system default.

Azul Zing 24.05.0.0 is now able to collect Falcon diagnostics during OOM (Out of memory) errors.

Thread-local backoff for secondary_super_cache updates has been ported from OpenJDK, based on JDK-8316180 and is disabled by default. To enable this feature, use the option -XX:SecondarySuperMissBackoff=1000.

A new command line option, OptimizeIdentityHashForDistribution has been introduced in Zing 24.05.0.0. This option enables an alternate implementation for System.identityHashCode() which provides better distribution of objects at the cost of making the identity hash calculation itself slower. This option is disabled by default and can be enabled using -XX:+OptimizeIdentityHashForDistribution.

There are no new issues to report in this release.