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  1. JDK
  2. JDK-8027959

Early reclamation of large objects in G1

    Details

    • Type: Enhancement
    • Status: Resolved
    • Priority: P4
    • Resolution: Fixed
    • Affects Version/s: hs25, 8
    • Fix Version/s: 9
    • Component/s: hotspot
    • Subcomponent:
      gc
    • Resolved In Build:
      b28

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        Description

        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

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