IV49284: JAVACORE FILES SLOW WHEN NUMBER OF MONITORS IS HIGH

APAR status

• Closed as program error.

Error description

• Error Message: javacore files take an excessive time to write
  when the number of monitors in the JVM (as listed in the
  javacore) is very high.
  javacores listing monitor counts of approximately 500,000 have
  been observed to take over 1 minute to write.
  .
  Stack Trace: Here is an example of part of a javacore, showing a
  large number of monitors:
  0SECTION       LOCKS subcomponent dump routine
  NULL           ===============================
  NULL
  1LKPOOLINFO    Monitor pool info:
  2LKPOOLTOTAL     Current total number of monitors: 595139
  If a core dump is taken during the slow javacore, the stack
  trace may be similar to:
  #0  in j9thread_monitor_walk_no_locking_with_lib()
  #1  in JavaCoreDumpWriter::writeMonitorSection()
  #2  in protectedWriteSection()
  ...etc
  .
  

Local fix

• No workaround available, other than reducing the number of
  monitors in use.
  

Problem summary

• The problem is caused when the JVM iterates over the monitors,
  to write them into the javacore.
  

Problem conclusion

• This defect will be fixed in:
  7.0.0 SR6
  6.0.1 SR7
  6.0.0 SR15
  .
  The JVM has been updated to optimise the algorithm used.
  

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

• R600 PSY

     UP