IJ31667: XGC:CLASSUNLOADINGKICKOFFTHRESHOLD NOT WORKING AS EXPECTED

APAR status

• Closed as program error.

Error description

• Error Message: N/A
  .
  Stack Trace: N/A
  .
  

Local fix

Problem summary

• When -Xgc:classUnloadingKickoffThreshold option is set,
  concurrent mark correctly begins when the threshold is reached,
  but its transition to the final STW phase can be incorrectly
  deferred.  This results in the global GC cleaning having
  approximately the same number of classes and classloaders to
  deal with, as if the option was not provided.
  

Problem conclusion

• Internally, concurrent phase of the global GC cycle consists of
  two major phases: tracing only and then tracing&card cleaning.
  It is the transition within these phases that is delayed,
  indirectly delaying the transition to the final STW phase. The
  delay is due to incorrect card cleaning kickoff threshold that
  is done as if the cycle was triggered by typical trigger - low
  free memory. The logic has been updated to adjust the card
  cleaning kickoff threshold to account for the actual
  (potentially high) free memory at the moment the cycle started.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR6 FP30  (8.0.6.30)
  .
  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

  J9 COMMON CODE

• Fixed component ID

  620700127

Applicable component levels

• R270 PSY

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