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Java Platform, Standard Edition Troubleshooting Guide
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NMT Memory Categories

Table 2-1 describes native memory categories used by NMT. These categories may change with the release.

Table 2-1 Native Memory Tracking Memory Categories

Category Description

Java Heap

The heap where your objects live


Class meta data


Generated code


data use by the GC, such as card table


Memory used by the compiler when generating code



Memory Tracking

Memory used by NMT itself

Pooled Free Chunks

Memory used by chunks in the arena chunk pool

Shared space for classes

Memory mapped to class data sharing archive


Memory used by threads, including thread data structure, resource area and handle area and so on.

Thread stack

Thread stack. It is marked as committed memory, but it might not be completely committed by the OS


Memory that does not fit the previous categories, such as the memory used by the command line parser, JVMTI, properties and so on.


When memory category can not be determined.

Arena: When arena is used as a stack or value object

Virtual Memory: When type information has not yet arrived

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