Java SE HotSpot at a Glance

The Java HotSpot Virtual Machine is a core component of the Java SE platform. It implements the Java Virtual Machine Specification, and is delivered as a shared library in the Java Runtime Environment. As the Java bytecode execution engine, it provides Java runtime facilities, such as thread and object synchronization, on a variety of operating systems and architectures. It includes dynamic compilers that adaptively compile Java bytecodes into optimized machine instructions and efficiently manages the Java heap using garbage collectors, optimized for both low pause time and throughput. It provides data and information to profiling, monitoring and debugging tools and applications.

HotSpot is an "ergonomic" JVM. Based upon the platform configuration, it will select a compiler, Java heap configuration, and garbage collector that produce good to excellent performance for most applications. Under special circumstances, however, specific tuning may be required to get the best possible performance. The resources collected here will help the reader understand and tune the Java HotSpot Virtual Machine.

Oracle is committed to a vibrant, participatory community supporting the Java Platform, Standard Edition (Java SE). Oracle will continue to make the Java Development Kit (JDK) and Java Runtime Environment (JRE) freely downloadable as well as continue support for the open-source implementation of Java SE via the OpenJDK project. With the Sun acquisition, Oracle has two major Java Virtual Machine (JVM) implementations, the Java HotSpot VM and the Oracle JRockit JVM. In the short-to-medium term, both will continue as strategic JVMs with active investment. Over time, Oracle plans to converge the functionality and code bases of these JVMs.

Technology

• HotSpot Engine Architecture
• HotSpot Thread Implementation (Solaris)
• HotSpot Garbage Collection
• HotSpot Class Data Sharing
• HotSpot Ergonomics
• HotSpot Performance and Tuning
• HotSpot Publications

Documentation

• Java VM Specification
• Java Native Interface (JNI) Specification
• Java Native Interface (JNI) Programmer's Guide
• HotSpot VM Command Line Options

Frequently Asked Questions

• HotSpot VM
• HotSpot VM Garbage Collection
• Performance Tools (jvmstat)

Forums

Several forums may help answer your questions:

• Java Technology Forum on Java Virtual Machine (JVM) on Sun Developer Network(SDN):
  Hotspot VM, Q&A forum, this is a great resource for all skill levels of developers.
• General Java Performance Forum on java.net.
  Discussion of Java related performance.
• Java Technology Forum on Java Runtime Environment (JRE) on Sun Developer Network (SDN):
  General Java, Q&A forum, this is a great resource for all developers new to Java.
• Java SE Snapshots: Project Feedback Forum in the JDK Forums on java.net:
  You can use this to leave us feedback on current snapshots.

HotSpot VM Changes