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  1. JDK
  2. JDK-8027959

Early reclamation of large objects in G1

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    • gc
    • b28

        In G1 large objects are always allocated in the old generation, requiring a complete heap liveness analysis (full gc, marking) to reclaim them.

        This is far from ideal for many transaction based enterprise applications that create large objects that are only live until a (typically short-lived) transaction is not completed (e.g. in a ResultSet of a JDBC query that generates a large result).
        This results in the heap filling up relatively quickly, typically leading to unnecessary marking cycles just to reclaim them.

        Investigate options to reclaim these objects more quickly; options found so far are:
        a) logically keep LOBs in young gen, doing in-place aging
        b) keep LOBs in the old gen, but use the remembered set and information from young collection to determine LOB liveness

          1. early_large_object_reclamation.png
            early_large_object_reclamation.png
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              tschatzl Thomas Schatzl
              tschatzl Thomas Schatzl
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