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  1. JDK
  2. JDK-8165443

Free Collection Set serial phase takes very long on large heaps

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    • Subcomponent:
      gc

      Description

      Even after fixing JDK-8165313, a significant amount of time is spent in the Free Collection Set Serial part of the GC.

      E.g. with -Xmx20g -Xms20g -XX:NewSizePercent=65 -XX:MaxNewSizePercent=80 -XX:G1RegionSize=1m on gcbasher, time spent in that phase is still in the range of 20ms (instead of >100ms) with ~14k regions.

      Running with analyzer enabled, the work distribution is kind of this (accumulated times of a single run in ms):

        G1SerialFreeCollectionSetClosure::doHeapRegion: 107
          G1CollectedHeap::free_region 38
          TruncatedSeq::add(double) 18
          SurvRateGroup::record_surviving_words 9
          G1COntiguousSpace::used 2

      (I kind of think that the TruncatedSeq::add() measurements were part of SurvRateGroup::record_surviving_words(), but somehow did not get attributed correctly)

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              • Assignee:
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                Reporter:
                tschatzl Thomas Schatzl
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                • Created:
                  Updated: