IJ04409: JAVA JIT: LONG GC PAUSE TIMES WHEN UNLOADING CLASSES

APAR status

• Closed as program error.

Error description

• Error Message: GC pause times that can be up to a few minutes in
  length.
  Verbose GC log example:
  <gc-op id="45470" type="classunload" timems="163058.757"
  contextid="45455" timestamp="2017-06-14T20:36:54.692">
  
    <classunload-info classloadercandidates="2461"
  classloadersunloaded="75" classesunloaded="944"
  anonymousclassesunloaded="0" quiescems="0.000" setupms="979.330"
  scanms="162078.954" postms="0.472" />
  </gc-op>
  .
  Stack Trace: N/A
  .
  If a system profile is taken (TProf/Perf) during the long GC
  pause, you would see the function detechFromRAT as the highest
  CPU consumer. The CPU utilization during the pause time would
  show that only one CPU core is working at 100% with other cores
  being idle.
  

Local fix

• N/A
  

Problem summary

• The JIT needs to manage a table of assumptions that have been
  made when methods are compiled. These assumptions allow the JIT
  to react when any assumption is broken as a result of new
  classes being loaded. In cases where the JIT has compiled a
  larger number of methods and the JVM is unloading classes during
  a GC cycle, it's possible for the JIT to take a long time to
  clean up any assumptions that have been registered against
  methods of the classes that are being unloaded.
  

Problem conclusion

• The process for cleaning up runtime assumptions in the JIT
  compiler has been improved such that it can execute much faster
  in cases were a larger number assumptions are being cleaned up
  during class unloading.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR5 FP11  (8.0.5.11)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  Service Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels