IV51086: EXTRA GC COMPACTIONS WHEN THE PREVIOUS SCAVENGE FAILED TO EXPAND

APAR status

• Closed as program error.

Error description

• Error Message: Unnecessary compactions happens with "failed to
  expand" reason for percolate collect.  Here is an example:
  <gc-op id="27717" type="scavenge" timems="261.868"
  contextid="27714" timestamp="2013-08-09T16:11:27.582">
    <scavenger-info tenureage="14" tiltratio="85" />
    <memory-copied type="nursery" objects="4782292"
  bytes="248767008" bytesdiscarded="265680" />
    <memory-copied type="tenure" objects="211023" bytes="12994312"
  bytesdiscarded="131992" />
    <copy-failed type="tenure" objects="4" bytes="737312" />
    <finalization candidates="49" enqueued="47" />
    <ownableSynchronizers candidates="206" cleared="174" />
    <references type="phantom" candidates="1" cleared="0"
  enqueued="0" />
  </gc-op>
  ....
  <af-start id="27735" totalBytesRequested="80"
  timestamp="2013-08-09T16:11:31.892" intervalms="4572.591" />
  <percolate-collect id="27736" from="nursery" to="global"
  reason="Previous scavenge failed to expand"
  timestamp="2013-08-09T16:11:31.892"/>
  <gc-start id="27737" type="global" contextid="27726"
  timestamp="2013-08-09T16:11:31.892">
  ....
  <gc-op id="27746" type="compact" timems="5445.129"
  contextid="27726" timestamp="2013-08-09T16:11:37.704">
    <compact-info movecount="55137760" movebytes="2048168416"
  reason="compact on aggressive collection" />
  </gc-op>
  .
  Stack Trace: N/A
  .
  

Local fix

Problem summary

• This compact reason "failed to expand" should be aggressive only
  if a subsequent scavenge leads to another percolate.
  

Problem conclusion

• This defect will be fixed in:
  7.0.0 SR7
  6.0.1 SR8
  .
  The JVM has been updated so that the compact reason for "failed
  to expand" is aggressive only if a subsequent scavenge leads to
  another percolate.
  If both "failed to expand" and "failed tenure" percolate
  conditions are met (which is often a case), "failed tenure"
  takes precedence.
  both are now treated equally, but the percolate reason in
  verbose gc will be reported as "failed tenure".
  

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

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