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Features Added in Older Releases of Azul Platform Prime Builds of OpenJDK

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This page lists new features in each release of Azul Zing Builds of OpenJDK (Zing) prior to


  1. Zing contains -XX:+FalconCompensateForIntelMCUForErratumSKX102 which is an off-by-default option and introduces a nop padding based mitigation for performance regressions seen on some systems following Intel’s microcode updates in response to errata SKX102. This option is expected to become the default in a future Zing release. If enabled, nop padding will be used to align affected branches on systems with the microcode update applied.

    For testing purposes, the flag -XX:+ForceFalconCompensateForIntelMCUForErratumSKX102 is also provided. This can be used to force the generation of nop padded code on unaffected systems for performance validation.


  • Zing is a critical patch update (CPU) release that contains security and critical bug fixes only. Zing is based on Zing and Zing and brings the associated JDK 7, JDK 8, and JDK 11 versions to January 2020 CPU security update levels.


  • Zing introduces additional non-security changes associated with the PSU 2019 OpenJDK 8u232 and OpenJDK 11.0.5 release contents.

  • The release of Zing provides further improved throughput and latency characteristics with heaps less than or equal to 1 GB.

  • The release of Zing provides enhanced escape analysis and a few other improvements in the Falcon JIT compiler, which may decrease the allocation rate and deliver higher performance on some workloads.

  • The release of Zing enhances the improvements of ReadyNow and Compile Stashing started in Zing, which now dramatically reduces CPU consumption for JIT compilation on many workloads..

  • Starting with Zing, Compile Stashing is not enabled by default with the -XX:ProfileLogOut command-line option. Compile Stashing is still enabled by default only in combination with the -XX:ProfileLogIn command-line option.


  • Zing introduces an option to write live memory objects into Zing flight recordings for troubleshooting memory leaks.

    Use the JFRDescribeLiveSetPercentage command-line option to tune the percentage amount of a live set to be described.

  • Due to providing better input from ReadyNow to Falcon and enabling Falcon to do better optimizations, Zing closes or significantly shortens a gap between ReadyNow and default Zing final throughputs in rare cases when the gap is observed.

    Note that in some cases doing better optimizations may lead to an increase in CPU consumption or startup time. In such cases, the new FalconOptimizationLevel command-line option can be used to lower the aggressiveness of optimizations. See Falcon Compiler Options for details.

  • Starting with Zing, Zing supports a heap size of 512 MB. The release of Zing adds improved Zing performance for heaps of less than 2 GB.

  • Zing significantly reduces CPU usage due to a new compilation policy and improvements in the Falcon compiler.

  • Zing features updated Zing MXBeans javadoc.

  • In Zing the default values for CodeCacheMinimumFreeSpace, CodeCacheOopTableSize and ReservedCodeCacheSize command-line options are changed to allow more space for objects in the Java heap with small heaps.

  • Zing introduces new Thread Local Allocation Buffer (TLAB) command-line options to resize TLABs and manage allocation of objects in TLABs.

  • In Zing, the default value of the AlignArrayStart command-line option is changed to true.

  • In Zing, the default value of the HserrRawCodeWindowSize command-line option is changed to 512.

  • Zing introduces a new MaxRAMPercentage command-line option for adjusting the maximum heap size based on the configured cgroup memory limit.


  • Zing incorporates additional non-security changes associated with the PSU 2019 OpenJDK 8u222 and OpenJDK 11.0.4 release contents.

  • Zing introduces the OpenJSSE TLS 1.3 JSSE provider which can be used to enable TLS 1.3 support with no application or code changes.

    Use the -XX:+UseOpenJSSE command-line option to enable TLS 1.3 support.

  • A new PrintGCHSLines command-line option for controling additional system information lines.


  • Zing brings the associated JDK 7, JDK 8, and JDK 11 versions to July 2019 CPU security update levels.

  • Starting with Zing the Zing Virtual Machine installs without the Zing System Tools component dependencies by default.

  • Zing introduces a new FalconOptimizationLevel command-line option for controling the level of compiling optimization.

  • Enhancements for the ReadyNow performance tuning tool.


  • Zing brings the associated JDK 7, JDK 8, and JDK 11 versions to July 2019 CPU security update levels.


  • Zing incorporates additional non-security changes associated with the April 2019 OpenJDK 8u212 and OpenJDK 11.0.3 release contents.

  • Zing JDK 8 supports JEP 328. The Java Flight Recorder feature records information about Zing VM and its environment while it is running.


  • The GPGCPausePreventionMemory command-line option is introduced to restrict pause prevention memory.

  • The ProfilePreMainTier2CompilerThreads, and ProfileWorkerThreads command-line options are added. The default value of ProfileStartupLimitInSeconds, is changed to 60.

  • The default value of the FalconUseAVX command-line option is changed to 2.

  • The default value of the ProfileStartupLimitInSeconds command-line option is changed to 60.

  • The default value of the ResetSignalMaskAtLaunch command-line option is changed to true.

  • The default value of the RunVMErrorOnUnhandledSignals command-line option is changed to true.


  • Zing applies fixes reflecting January 2019 OpenJDK 7u211, OpenJDK 8u201, OpenJDK 8u202, and OpenJDK 11.0.2 changes.

  • A new gcLogScraper script is introduced for easy parsing of GC log files.

  • The speed of the existing Datagram Channel is dramatically improved.

  • The -XX:[+/-] UseStringDeduplication command-line option is now back to being product and is ignored by the VM.


  • The MaxDirectMemorySize command-line option changed its type to unsigned and no longer accepts negative values. Its default value is changed from -1 to 0 while preserving the corresponding default behavior.


  • Fixes reflecting July 2018 OpenJDK 8u181 and 7u191 critical patch updates provided.


  • Fixes reflecting April 2018 OpenJDK 8u172 and 7u181 changes provided.


  • Compiler Statistics Reporting Updates:

    • Adding total wait-in-queue time to compiler statistic reporting and GC log records.

    • Changing TotalAcutalTimeMS to TotalCPUTimeMS in GC log records and compiler statistics.

  • Performance and stability improvements.


  • Unlimited Cryptographic Policy is Enabled by Default.

  • Providing Azul OEM Master License Key.

  • Enhancements for gcLogAnalyser.

  • Compiler Enhancements including Using Compile Stashing.

  • Deprecation of Support for RHEL 5


  • Enhance control of precompilation to allow control of each tier’s precompliation separately.

  • Add support for uncounted loop safepoint removal.

  • Add a command-line option that changes the threshold at which the OSR compiles are triggered.

  • Enhance the gcLogAnalyser tool’s graph PNG file generator to automatically add html pages to:

    • Easily navigate the graphs in a set of PNG files using a web browser

    • Compare any two graphs in one view using a web browser


  • Include JCE Jurisdiction Policy files.

  • Set limit on array length.

  • CodeCache flushing improvements.

  • New Falcon inlining command-line option.

  • ReadyNow enhancements.


  • Increase maximum heap size (-Xmx) supported by Zing from 2 TB to 8 TB.


  • The ZST 5.20 that is included in the Zing Trial Program has two new behaviors. First, system-config-zing-memory is run automatically after the installation of the ZST to configure the System Zing Memory. Second, the default policy for reservation of memory used by the Zing has been changed from reserve-at-config (reserved when system-config-zing-memory is run) to reserve-at-launch (reserved when the Zing process is launched).

  • Support for Stop-The-World (STW) garbage collection in the Zing.

  • Multiple changes and improvements in the GC Log Analyser tool.

  • Enable CodeCache Flushing and support for ParallelClassLoaders.


  • Falcon compiler becomes the default Tier 2 compiler for Zing (for Java SE 7 and 8) replacing C2.

  • Multiple changes and improvements in the Zing monitoring tools.

  • Many improvements of the ReadyNow performance tuning tool.


  • General Availability of the Falcon Compiler.

  • Adding the UseFastJNIAccessors option to the list of the unchangeable options.

  • Adding the ability to process files that have GC log lines without any timestamp preceding the log line label.


  • Increased number of supported operating systems and kernels.

  • Compiler Enhancements.

  • Performance and Stability Improvements


  • Intel TSX support

  • Additions to the Garbage Collector output information

  • Enhancements in the gcLogAnalyser tool

  • Large number of supported operating systems and kernels

  • Performance Improvements.


  • Extended Java Heap Size up to 2 TB per JVM instance

  • The Native Memory Tracking functionality includes invocation of Memory-tracking functions to record allocations.

  • New graphs are available in the gcLogAnalyser tool.

  • Bug fixes.