Java in a Nutshell, 5th Edition

Name

jmap — Display memory usage

Synopsis

jmap [ options ] pid                       // local process
jmap [ options ] executable 
                  core           // core file
jmap [ options ] [process-name@]hostname   // remote process

Description

jmap prints memory usage information for a local or remote Java process or a Java core file. Depending on the option it is invoked with, jmap displays one of four memory usage reports. See the Options section for details. jmap can be started in three ways:

• Specify the process id of a Java process running locally to obtain configuration information about it. See jps to list local processes.

• To obtain post-mortem configuration information from a core file, specify the java executable that produced the core file and the core file itself on the command line.

• To obtain configuration information about a Java process running remotely, specify the name of the remote host, optionally prefixed by a remote process name and @ sign. jsadebugd must be running on the remote host.

In Java 5.0, jmap is experimental, unsupported, and not available on all platforms.

Options

When invoked with no options, jmap prints a memory map of the shared objects or libraries loaded by the VM. Other reports can be produced by using the options below. These options are mutually exclusive; only one may be specified.

-heap

Displays a summary of heap memory usage.

-help, -h

Prints a help message.

-histo

Displays a histogram of heap usage by class.

-permstat

Displays memory used by loaded classes, grouped by class loader.

See also ...