HotSpot
| Developer(s) | Oracle Corporation (previously Sun Microsystems) |
|---|---|
| Initial release | April 27, 1999 |
| Stable release |
23.25-b01
|
| Written in | C++ |
| Operating system | Cross-platform |
| Type | Java Virtual Machine |
| License | Proprietary (early versions), GNU General Public License (current) |
| Website | Sun's OpenJDK Hotspot page |
HotSpot, released as the "Java HotSpot Performance Engine" is a Java virtual machine for desktops and servers, maintained and distributed by Oracle Corporation. It features techniques such as just-in-time compilation and adaptive optimization designed to improve performance.
The Java Hot-Spot Performance Engine, first released April 27, 1999, built on technologies from the Strongtalk implementation of the Smalltalk programming language originally developed by Longview Technologies, which traded as "Animorphic". A Sun research project, the Self programming language, had earlier successfully used Animorphic's virtual-machine technology. In 1997 Sun Microsystems purchased Animorphic.
Shortly after acquiring Animorphic, Sun decided to write a new just-in-time (JIT) compiler for the Java virtual machine. This new compiler would give rise to the name "HotSpot", which derives from the fact that, as the software runs Java bytecode, 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. In one report, the JVM beat some C++ or C code in certain benchmarks.
Initially available as an add-on for Java 1.2, HotSpot became the default Sun JVM in Java 1.3.
Sun's JRE features two virtual machines, one called Client and the other Server. The Client version is tuned for quick loading. It makes use of interpretation. The Server version loads more slowly, putting more effort into producing highly optimized JIT compilations, that yield higher performance. Both VMs compile only often-run methods, using a configurable invocation-count threshold to decide which methods to compile.
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