jmap - Memory Map
SYNOPSIS
jmap [ option ] pid
jmap [ option ] executable core
jmap [ option ] [server-id@]remote-hostname-or-IP
PARAMETERS
- option
- Options are mutually exclusive. Option, if used, should
follow immediately after the command name.
- pid
- process id for which the memory map is to be printed. The
process must be a Java process. To get a list of Java processes
running on a machine, jps may be
used.
- executable
- Java executable from which the core dump was produced.
- core
- core file for which the memory map is to be printed.
- remote-hostname-or-IP
- remote debug server's (see jsadebugd) hostname or IP address.
- server-id
- optional unique id, if multiple debug servers are running on
the same remote host.
DESCRIPTION
jmap prints shared object memory maps or heap memory
details of a given process or core file or a remote debug server.
If the given process is running on a 64-bit VM, you may need to
specify the -J-d64 option, e.g.:
jmap -J-d64 -heap pid
NOTE: This utility is unsupported and may or may not be
available in future versions of the JDK. In Windows Systems where
dbgeng.dll is not present, 'Debugging Tools For Windows' needs to
be installed to have these tools working. Also, PATH
environment variable should contain the location of
jvm.dll used by the target process or the location
from which the Crash Dump file was produced.
For example, set PATH=<jdk>\jre\bin\client;%PATH%
- <no option>
- When no option is used jmap prints
shared object mappings. For each shared object loaded in the
target VM, start address, the size of the mapping, and the full
path of the shared object file are printed. This is similar to
the Solaris pmap utility.
- -dump:[live,]format=b,file=<filename>
- Dumps the Java heap in hprof binary format to filename. The
live suboption is optional. If specified, only the live
objects in the heap are dumped. To browse the heap dump, you can
use jhat (Java Heap Analysis Tool) to
read the generated file.
- -finalizerinfo
- Prints information on objects awaiting finalization.
- -heap
- Prints a heap summary. GC algorithm used, heap configuration
and generation wise heap usage are printed.
- -histo[:live]
- Prints a histogram of the heap. For each Java class, number
of objects, memory size in bytes, and fully qualified class names
are printed. VM internal class names are printed with '*' prefix.
If the live suboption is specified, only live objects are
counted.
- -permstat
- Prints class loader wise statistics of permanent generation
of Java heap. For each class loader, its name, liveness, address,
parent class loader, and the number and size of classes it has
loaded are printed. In addition, the number and size of interned
Strings are printed.
- -F
- Force. Use with jmap -dump or jmap -histo option if the pid
does not respond. The live suboption is not supported in
this mode.
- -h
- Prints a help message.
- -help
- Prints a help message.
- -J<flag>
- Passes <flag> to the Java virtual machine on which jmap
is run.
