HotSpot
From Wikipedia, the free encyclopedia
| Developer(s) | Sun Microsystems |
|---|---|
| Stable release | 14.0-b16 |
| Operating system | Cross-platform |
| Type | Java Virtual Machine |
| License | GNU General Public License |
| Website | Sun's OpenJDK Hotspot page |
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. Animorphic's virtual machine technology had earlier been successfully used in a Sun research project, the Self programming language. In 1997, Longview Technologies, LLC (DBA Animorphic) was purchased by Sun Microsystems[1]. Initially available as an add-on for Java 1.2, HotSpot became the default Sun JVM in Java 1.3[2].
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. It is possible for adaptive optimization of a JVM to exceed the performance of hand-coded C++ or assembly language code[3].
[edit] Features
Sun's JRE features 2 virtual machines , one called Client and the other Server. The Client version is tuned for quick loading. It makes use of interpretation, compiling only often-run methods. The Server version loads more slowly, putting more effort into producing highly optimized JIT compilations, that yield higher performance.
The HotSpot Java Virtual Machine is written in C++. As stated in HotSpot web page, the code contains approximately 250,000 lines of code[4]. Hotspot provides:
- A class loader,
- A bytecode interpreter,
- Client and a Server virtual machines, optimised for their respective uses
- Several garbage collectors,
- A set of supporting runtime libraries.
[edit] JVM flags
HotSpot supports many Command-line arguments for tweaking the Virtual Machine at launch. Some are standard and must be found in any conforming JVM, others are specific to HotSpot and may not be found in other JVMs (options that begin with -X or -XX are non-standard)[5][6][7][8].
[edit] License
On 13 November 2006, the Sun JVM and JDK were made available[9] under the GPL license (see Sun's OpenJDK Hotspot page).
[edit] Supported platforms
[edit] Maintained by Sun Microsystems
As for the whole JDK, HotSpot is currently supported by Sun on Microsoft Windows, Linux, and Solaris. Supported ISAs are IA-32, x86-64 and SPARC (exclusive to Solaris).[10]
[edit] Ports by third parties
Ports are also available by third parties for Mac OS X and various other Unix Operating systems. A number of different hardware architectures are also supported, including x86, PowerPC, and SPARC (Solaris only).
[edit] Obstacles to porting
Ports of HotSpot are difficult because the code, while primarily written in C++, contains a lot of assembly[11]. To remedy this, the IcedTea project has developed a generic port of the HotSpot interpreter called zero-assembler Hotspot (or zero), with almost no assembly code. This port is intended to allow the interpreter part of HotSpot to be very easily adapted to any Linux processor architecture, potentially making it infinitely portable. The code of zero-assembler Hotspot is used for all the non-x86 ports of HotSpot (PPC, IA64, S390 and ARM) since version 1.6[12][13][14].
Gary Benson, an IcedTea developer, is now developing a platform-independent Just-in-time compiler called Shark for HotSpot, using LLVM, to complement zero[15][16].
[edit] See also
- List of Java virtual machines
- Java performance
- OpenJDK
- Da Vinci Machine, a starting Sun project aiming to prototype the extension of the JVM to add support for dynamic languages
- Java Virtual Machine heap
- Comparison of application virtual machines
[edit] References
- ^ "Sun's Gosling Previews Hotspot Java Virtual Machine". ComputerGram. 1998-02-13. http://findarticles.com/p/articles/mi_m0CGN/is_n3348/ai_20359903/pg_1. Retrieved 2008-04-20.
- ^ "Sun Microsystems releases fastest client-side Java platform to date". Sun Microsystems. 2000-05-08. http://www.sun.com/smi/Press/sunflash/2000-05/sunflash.20000508.3.xml. Retrieved 2007-10-03.
- ^ Lewis, J.P. (2004). "Performance of Java versus C++". http://scribblethink.org/Computer/javaCbenchmark.html. Retrieved 2007-10-03.
- ^ "The HotSpot Group". Sun Microsystems. 2007. http://openjdk.java.net/groups/hotspot/. Retrieved 2007-10-03. "There are nearly 1500 C/C++ header and source files, comprising almost 250,000 lines of code"
- ^ "Java HotSpot VM Options". Sun Microsystems. http://java.sun.com/javase/technologies/hotspot/vmoptions.jsp. Retrieved 2009-02-08.
- ^ Mocker, Joseph D. (2007-08-28). "A Collection of JVM Options". http://blogs.sun.com/watt/resource/jvm-options-list.html. Retrieved 2009-02-08.
- ^ Maximovich, Dmitri. "The most complete list of -XX options for Java 6 JVM". http://www.md.pp.ru/%7Eeu/jdk6options.html. Retrieved 2009-02-08.
- ^ Nutter, Charles (2009-01-29). "My Favorite Hotspot JVM Flags". http://blog.headius.com/2009/01/my-favorite-hotspot-jvm-flags.html. Retrieved 2009-02-08.
- ^ "Sun Opens Java". Sun Microsystems. 2006-11-13. http://www.sun.com/aboutsun/media/presskits/2006-1113/. Retrieved 2007-10-03.
- ^ "Supported System Configurations". Sun Microsystems. http://java.sun.com/javase/6/webnotes/install/system-configurations.html. Retrieved 2008-01-26.
- ^ Gary, Benson (2007-11-06). "Gary's guide to porting IcedTea". http://gbenson.livejournal.com/2007/11/16/. Retrieved 2008-01-26.
- ^ Gary, Benson (2008-02-01). "1st February 2008". http://gbenson.livejournal.com/2008/02/01/. Retrieved 2008-02-03.
- ^ Andrew, Haley (2008-01-31). "Making zero-assembler the default on ppc". http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2008-January/001085.html. Retrieved 2008-02-03.
- ^ Lilian, Angel (2008-02-13). "IcedTea 1.6 Released with Zero-assembler and JNLP support!". Red hat. http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2008-February/001172.html. Retrieved 2008-02-13.
- ^ Gary, Benson (2008-03-31). "31 March 2008". Red hat. http://gbenson.net/?p=67. Retrieved 2008-05-30.
- ^ Gary, Benson (2008-05-28). "28 May 2008". Red hat. http://gbenson.net/?p=80. Retrieved 2008-05-30. "Shark is a platform-independent JIT for HotSpot, to complement the zero-assembler interpreter we’ve been using"
[edit] External links
- Sun's OpenJDK Hotspot page
- Sun's HotSpot information page
- HotSpot performance whitepaper
- 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
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