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  1. JDK
  2. JDK-8134857

Inconsistency in maximum TLAB/PLAB size and humonguous object size

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: P4
    • Resolution: Fixed
    • Affects Version/s: 9
    • Fix Version/s: 9
    • Component/s: hotspot
    • Labels:
    • Subcomponent:
      gc
    • Resolved In Build:
      b83

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        Description

        In G1CollectedHeap::max_tlab_size(), the maximum TLAB size is defined as

          align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);

        but G1CollectedHeap::is_humongous(size_t word_size) determines humonguous objects as

          word_size > _humongous_object_threshold_in_words

        Which means that G1CollectedHeap::max_tlab_size() is actually one word too small.

        Also _filler_array_max_size is equal to _humongous_object_threshold_in_words (not -1), so that "- 1" seems some arbitrary difference.

        This is very annoying with JDK-8078555 now checking these requirements, and the user wanting to set half region size as PLAB/TLAB size. :)

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                Assignee:
                tschatzl Thomas Schatzl
                Reporter:
                tschatzl Thomas Schatzl
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                  Updated:
                  Resolved: