IZ69014: ERRANT ENTRIES FOR TRACETARGET, KICKOFF ATTRIBUTES IN VERBOSEGC

APAR status

• Closed as program error.

Error description

• Error Message: Verbosegc Output showing huge errant values for
  the attributes tracetarget and kickoff.  Here's a sample:
  <con event="kickoff" timestamp="Sat Oct 31 11:34:45 2009">
  
    <stats tenurefreebytes="0" nurseryfreebytes="112131288"
  tracetarget="10145709460442578944" kickoff="1268213682555469598"
  tracerate="1961.12" />
  </con>
  Also an outage for about 5 minutes is observed usually when
  these entries are seen in the verbosegc output.
  .
  Stack Trace: N/A
  .
  

Local fix

• There is no real work around.  The only solution is to run with
  -Xgcpolicy:opthtruput or to get a VM with the fix.
  

Problem summary

• This problem is specific to GC policies using concurrent
  collector (that is, gencon or optavgpause). The errant verbosegc
  entries were caused by a divide by 0.  A divide by 0 when using
  floating point values results in a NAN.  When this value is
  converted back to an unsigned integer the number is very large.
  This large number would cause the GC to kick off another
  concurrent collection immediately since the amount of free
  memory would never be larger than this errant number, resulting
  in a consecutive concurrent collections for a few times and
  hence an outage in the customer environment.
  

Problem conclusion

• This defect will be fixed in:
  5.0.0 SR12
  .
  Concurrent GC code has been updated to check to see how much
  trace work was completed concurrently and if this value is 0
  then do not adjust the kick off value.
  .
  To obtain the fix:
  Install build 20100204 or later
  

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

  JAVA 5 J9 COMMO

• Fixed component ID

  620500127

Applicable component levels

• R500 PSN

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