Thursday, January 31, 2013

Here a Few Java Commands that Can Use Full

Hung, Dejava.lang.OutOfMemoryError: nativeGetNewTLAadlocked, or Looping Process

Print thread stack for all Java threads:
kill -QUIT pid
jstack pid (or jstack -F pid if jstack pid does not respond)

Detect deadlocks:
Request deadlock detection: JConsole tool, Threads tab
Print information on deadlocked threads: Control-\
Print list of concurrent locks owned by each thread: -XX:+PrintConcurrentLocks set, then Control-\
Print lock information for a process: jstack -l pid

Get a heap histogram for a process:
Start Java process with -XX:+PrintClassHistogram, then Control-\
jmap -histo pid (with -F option if pid does not respond)

Dump Java heap for a process in binary format to file:
jmap -dump:format=b,file= filename pid (with -F option if pid does not respond)

Print shared object mappings for a process:
jmap pid

Print heap summary for a process:
jmap -heap pid

Print finalization information for a process:
jmap -finalizerinfo pid

Attach the command-line debugger to a process:
jdb -connect sun.jvm.hotspot.jdi.SAPIDAttachingConnector:pid= pid

Post-mortem Diagnostics, Memory Leaks

  • Examine the fatal error log file. Default file name is hs_err_pid pid .log in the working-directory.
  • Create a heap dump:
    • Start the application with HPROF enabled: java -agentlib:hprof=file= file,format=b application; then Control-\
    • Start the application with HPROF enabled: java -agentlib:hprof=heap=dumpapplication
    • JConsole tool, MBeans tab
    • Start VM with -XX:+HeapDumpOnOutOfMemoryError; if OutOfMemoryError is thrown, VM generates a heap dump.
  • Browse Java heap dump:
    • jhat heap-dump-file
  • Dump Java heap from core file in binary format to a file:
    • jmap -dump:format=b,file= filename corefile
  • Get a heap histogram for a process:
    • Start Java process with -XX:+PrintClassHistogram, then Control-\
    • jmap -histo pid (with -F option if pid does not respond)
  • Get a heap histogram from a core file:
    • jmap -histo corefile
  • Print shared object mappings from a core file:
    • jmap corefile
  • Print heap summary from a core file:
    • jmap -heap corefile
  • Print finalization information from a core file:
    • jmap -finalizerinfo corefile
  • Print Java configuration information from a core file:
    • jinfo corefile
  • Print thread trace from a core file:
    • jstack corefile
  • Print lock information from a core file:
    • jstack -l corefile
  • Attach the command-line debugger to a core file on the same machine:
    • jdb -connect sun.jvm.hotspot.jdi.SACoreAttachingConnector:javaExecutable= path,core= corefile
  • Attach the command-line debugger to a core file on a different machine:
    • On the machine with the core file: jsadebugd path corefile
      and on the machine with the debugger: jdb -connect sun.jvm.hotspot.jdi.SADebugServerAttachingConnector:debugServerName=
  • libumem can be used to debug memory leaks.


Note: The vmID argument for the jstat command is the virtual machine identifier.

  • Print statistics on the class loader:
    • jstat -class vmID
  • Print statistics on the compiler:
    • Compiler behavior: jstat -compiler vmID
    • Compilation method statistics: jstat -printcompilation vmID
  • Print statistics on garbage collection:
    • Summary of statistics: jstat -gcutil vmID
    • Summary of statistics, with causes: jstat -gccause vmID
    • Behavior of the gc heap: jstat -gc vmID
    • Capacities of all the generations: jstat -gccapacity vmID
    • Behavior of the new generation: jstat -gcnew vmID
    • Capacity of the new generation: jstat -gcnewcapacity vmID
    • Behavior of the old and permanent generations: jstat -gcold vmID
    • Capacity of the old generation: jstat -gcoldcapacity vmID
    • Capacity of the permanent generation: jstat -gcpermcapacity vmID
  • Monitor objects awaiting finalization:
    • JConsole tool, VM Summary tab
    • jmap -finalizerinfo pid
    • getObjectPendingFinalizationCount method class
  • Monitor memory:
    • Heap allocation profiles via HPROF: java -agentlib:hprof=heap=sites
    • JConsole tool, Memory tab
    • Control-\ prints generation information.
  • Monitor CPU usage:
    • By thread stack: java -agentlib:hprof=cpu=samples application
    • By method: java -agentlib:hprof=cpu=times application
    • JConsole tool, Overview and VM Summary tabs
  • Monitor thread activity:
    • JConsole tool, Threads tab
  • Monitor class activity:
    • JConsole tool, Classes tab

Actions on a Remote Debug Server

First, attach the debug daemon jsadebugd, then execute the command:
  • Dump Java heap in binary format to a file: jmap -dump:format=b,file= filename hostID
  • Print shared object mappings: jmap hostID
  • Print heap summary : jmap -heap hostID
  • Print finalization information : jmap -finalizerinfo hostID
  • Print lock information : jstack -l hostID
  • Print thread trace : jstack hostID
  • Print Java configuration information: jinfo hosted

Other Functions

  • Interface with the instrumented Java virtual machines:
    • Monitor for the creation and termination of instrumented VMs: jstatd daemon
    • List the instrumented VMs: jps
    • Provide interface between remote monitoring tools and local VMs: jstatd daemon
    • Request garbage collection: JConsole tool, Memory tab
  • Print Java configuration information from a running process:
    • jinfo pid
  • Dynamically set, unset, or change the value of certain Java VM flags for a process:
    • jinfo -flag flag
  • Print command-line flags passed to the VM:
    • jinfo -flags
  • Print Java system properties:
    • jinfo -sysprops
  • Pass a Java VM flag to the virtual machine:
    • jconsole -J flag ...
    • jhat -J flag ...
    • jmap -J flag ...
  • Print statistics of permanent generation of Java heap, by class loader:
    • jmap -permstat
  • Report on monitor contention.
    • java -agentlib:hprof=monitor=y application
  • Evaluate or execute a script in interactive or batch mode:
    • jrunscript
  • Interface dynamically with an MBean, via JConsole tool, MBean tab:
    • Show tree structure.
    • Set an attribute value.
    • Invoke an operation.
    • Subscribe to notification.
  • Run interactive command-line debugger:
    • Launch a new VM for the class: jdb class
    • Attach debugger to a running VM: jdb -attach address

From oracle, More to Come