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It has been suggested that this article or section be merged into Java Virtual Machine. (Discuss) |
The Java Virtual Machine heap is the area of memory used by the Java Virtual Machine (and specifically HotSpot) for dynamic memory allocation[1].
The heap is split up into "generations":
- The Young generation store short-lived Objects that are created and immediately Garbage collected.
- Objects that persist longer are moved to the Old generation (also called Tenured generation).
- The Permanent Generation is used for class definitions.
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Permanent Generation
A separate area of the heap called Permanent generation (or permgen) is used to store class definitions and the associated Metadata[2][3].
There was originally no permanent generation, and Objects and classes were just stored together in the same area. But as class unloading occur much more rarely than Objects are collected, moving class structures to a specific area allows significant performance improvements[2].
See also
References
- ^ "Frequently Asked Questions about Garbage Collection in the Hotspot Java Virtual Machine". Sun Microsystems. 6 February 2003. http://java.sun.com/docs/hotspot/gc1.4.2/faq.html. Retrieved 7 February 2009.
- ^ a b Masamitsu, Jon (28 November 2006). "Presenting the Permanent Generation". http://blogs.sun.com/jonthecollector/entry/presenting_the_permanent_generation. Retrieved 7 February 2009.
- ^ Nutter, Charles (11 September 2008). "A First Taste of InvokeDynamic". http://blog.headius.com/2008/09/first-taste-of-invokedynamic.html. Retrieved 7 February 2009.
External links
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