IV59885: MULTIPLE EXCLUSIVE ACCESS EVENTS REPORTED FOR CONCURRENT KICKOFF IN VERBOSE GC LOGS

APAR status

• Closed as program error.

Error description

• Error Message: none
  .
  Stack Trace:
  .
  Sample for the concurrent kickoff and exclusive access events in
  verbose GC logs:<concurrent-kickoff id="3073"
  timestamp="2013-10-22T00:04:07.656"><kickoff reason="threshold
  reached" targetBytes="640090591" thresholdFreeBytes="88578344"
  /></concurrent-kickoff><exclusive-start id="3074"
  timestamp="2013-10-22T00:04:07.682"
  intervalms="5898.568"><response-info timems="0.256"
  idlems="0.093" threads="6" lastid="0000000001DAC300"
  lastname="Thread-40" /></exclusive-start><cycle-start id="3075"
  type="global" contextid="0" timestamp="2013-10-22T00:04:07.682"
  intervalms="392863.183" /><exclusive-end id="3076"
  timestamp="2013-10-22T00:04:07.682" durationms="0.164"
  /><exclusive-start id="3077" timestamp="2013-10-22T00:04:07.682"
  intervalms="0.179"><response-info timems="0.001" idlems="0.001"
  threads="0" lastid="0000000001709B00" lastname="Thread-18"
  /></exclusive-start><exclusive-end id="3078"
  timestamp="2013-10-22T00:04:07.682" durationms="0.016"
  /><exclusive-start id="3079" timestamp="2013-10-22T00:04:07.683"
  intervalms="0.032"><response-info timems="0.001" idlems="0.001"
  threads="0" lastid="00000000016D3500" lastname="Thread-43"
  /></exclusive-start><exclusive-end id="3080"
  timestamp="2013-10-22T00:04:07.683" durationms="0.030" />...
  many additional exclusive events ...<exclusive-start id="3153"
  timestamp="2013-10-22T00:04:07.806"
  intervalms="122.347"><response-info timems="0.329"
  idlems="0.161" threads="39" lastid="0000000001E22200"
  lastname="Thread-16"
  /></exclusive-start><concurrent-collection-start id="3154"
  timestamp="2013-10-22T00:04:07.807" intervalms="392851.710" />
  

Local fix

Problem summary

• In some workloads multiple application threads may
  simultaneously detect that a concurrent GC should be triggered,
  and each will attempt to acquire exclusive VM access to perform
  the concurrent kickoff. The first thread to acquire exclusive
  access will perform the necessary actions; subsequent threads
  will each acquire exclusive VM access, determine that no action
  is required, and release.Each time a thread acquires exclusive
  VM access, an event is written to the GC verbose log. In the
  situation described this results in extra log entries. This can
  be a particular problem when rotating logs are used, since the
  additional entries reduce the number of informative entries that
  appear in each log file.
  

Problem conclusion

• This APAR will be fixed in the following Java Releases:
     7    SR7 FP1   (7.0.7.1)
     7 R1 SR1 FP1   (7.1.1.1)
     6 R1 SR8 FP1   (6.1.8.1)
  .
  Triggering concurrent GC has been serialized so a single
  exclusive VM access event will be reported for concurrent
  kickoff.
  

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

• R260 PSY

     UP

• R270 PSY

     UP