What is perm space?

java profiling
skiphoppy picture skiphoppy · Aug 14, 2009 · Viewed 107k times · Source

While learning about java memory profiling, I keep seeing the term "perm space" in addition to "heap." I know what the heap is - what's perm space?

Answer

Andrew Hare picture Andrew Hare · Aug 14, 2009

It stands for permanent generation:

The permanent generation is special because it holds meta-data describing user classes (classes that are not part of the Java language). Examples of such meta-data are objects describing classes and methods and they are stored in the Permanent Generation. Applications with large code-base can quickly fill up this segment of the heap which will cause java.lang.OutOfMemoryError: PermGen no matter how high your -Xmx and how much memory you have on the machine.

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