HotSpot
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| HotSpot | |
| Latest release: | 1.6 |
|---|---|
| OS: | Cross-platform |
| Use: | Java Virtual Machine |
| License: | GNU General Public License |
| Website: | http://java.sun.com/products/hotspot/ |
HotSpot is the primary Java Virtual Machine for desktops and servers produced by Sun Microsystems. It features techniques such as just-in-time compilation and adaptive optimization designed to improve performance.
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[edit] History
HotSpot, first released April 27, 1999, was originally developed by Longview Technologies, LLC which was doing business as Animorphic, a small startup company formed in 1994. In 1997, Lonview Technologies, LLC (DBA Animorphic) was purchased by Sun Microsystems. Initially available as an add-on for Java 1.2, HotSpot became the default Sun JVM in Java 1.3. [1]
Its name derives from the fact that as it runs Java byte-code, it continually analyzes the program's performance for "hot spots" which are frequently or repeatedly executed. These are then targeted for optimization, leading to high performance execution with a minimum of overhead for less performance-critical code. HotSpot is widely acclaimed as providing the best performance in its class of JVM. In theory, though rarely in practice, it is possible for adaptive optimization of a JVM to exceed hand-coded C++ or assembly language [2].
[edit] Features
In Sun's JRE, it consists of two interchangeable versions, one called Client and the other Server. The Client version is tuned for quick loading and compilation of essential classes and methods only. The Server version loads more slowly but puts more effort into producing highly optimized JIT compilations that yield higher performance.
The HotSpot Java Virtual Machine is written in C++ [3]. As stated in HostSpot web page, the code contains approximately 250,000 lines of code. Hotspot provides :
- A class loader,
- A bytecode interpreter,
- A Client and a Server runtime compilers from bytecode to native instructions,
- Several garbage collectors,
- A set of supporting runtime libraries.
[edit] License
On 13 November 2006, the Sun JVM and JDK were made available[4] under the GPL license (see Sun's OpenJDK Hotspot page).
[edit] See also
[edit] External links
- Sun's OpenJDK Hotspot page
- Sun's HotSpot information page
- A list of HotSpot VMOptions
- The Java Virtual Machine Specification
- The history of the original Strongtalk/HotSpot team
- Sun announces availability of the Java Hotspot Performance Engine
