jmap - JVM Heap Dump Tool

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∟jmap - JVM Heap Dump Tool

This section describes the JVM heap dump tool, 'jmap', command and its options. Windows version of 'jmap' can print heap histogram and generate heap dump.

What Is "jmap"? - "jmap" (Java memory Map) is tool to print shared object memory maps or heap memory details of a given JVM process or a Java core file on the local machine or on a remote machine through a debug server.

The "jmap" tool included in the Windows version of JDK supports functions to print histogram of Java object heap and generate a heap dump of a given JVM process:

herong> jmap

Usage:
    jmap -clstats <pid>
        to connect to running process and print class loader statistics
    jmap -finalizerinfo <pid>
        to connect to running process and print information on objects
        awaiting finalization
    jmap -histo[:live] <pid>
        to connect to running process and print histogram of java object
        heap if the "live" suboption is specified, only count live objects
    jmap -dump:<dump-options> <pid>
        to connect to running process and dump java heap

    dump-options:
      live         dump only live objects; if not specified,
                   all objects in the heap are dumped.
      format=b     binary format
      file=<file>  dump heap to <file>

    Example: jmap -dump:live,format=b,file=heap.bin <pid>