User Guide

Introduction

• Free, customized and optimized OpenJDK version
• Based on OpenJDK 11, compatible with Java standard interfaces, and certified as compatible with the Java SE standard.
• After the internal testing and use of multiple systems in the data platform department, the stability is highly guaranteed
• Support new features such as large GC optimization, memory resource cost optimization, and continuous optimization for scenarios such as big data, machine learning, cloud scenarios, and microservices
• Quarterly synchronization to ensure safe updates

ZGC optimization

• FEAT(zgc): Concurrent Class Unloading，Reduce pause time by 50%
• FEAT(zgc): Redesign C2 load barrier，Improve ZGC stability

G1 GC optimizations

• Backport of JEP 344: Abortable Mixed Collections for G1 GC
• More information in JEP 344

Print additional information in thread dump

• Using jstack or jcmd to do thread dump, get more information as below：
  • cpu = ...: the time the thread spent executing on the CPU
  • elapsed = ...: the wall clock time passed since the thread was started.
  • allocated=... : The number of bytes allocated by this thread.
  • defined_classes=... : The number of classes defined by this thread
• The values 'allocated=' and 'defined_classes=' are only printed if the VM is started with -XX:+PrintExtendedThreadInfo.
• If the thread dumps are gathered by jcmd, '-e' must be added to the Thread.print command.

ZGC is turned on for trial

-- use -XX:+UnlockExperimentalVMOptions -XX:+UseZGC to enable ZGC