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  1. JDK
  2. JDK-8152724

Sum of eden before GC and current survivor capacity may be larger than heap size

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: P4
    • Resolution: Fixed
    • Affects Version/s: 8u74, 9
    • Fix Version/s: 12
    • Component/s: hotspot
    • Subcomponent:
      gc
    • Resolved In Build:
      b24

      Backports

        Description

        G1 calculates survivor capacity based on eden capacity and SurvivorRatio (literally current_eden_capacity / SurvivorRatio).

        If eden capacity is very large, e.g. set by limiting min young gen size by G1NewSizePercent to something > 50%, and SurvivorRatio=1, the total of eden, survivor and old gen capacities will exceed total heap size.

        This is just an issue with logging, e.g. on a 256M heap it is possible that the following log output is given:

        [2.335s][info ][gc,heap ] GC(0) Eden regions: 153->0(133)
        [2.335s][info ][gc,heap ] GC(0) Survivor regions: 0->20(133)

        I.e. eden size before gc + survivor capacity = 286 regions, which are more regions than available in the heap.

        The problem is that in the calculation of the next survivor capacity in G1CollectorPolicy::update_survivors_policy() does not guarantee consistency.

        This seems to only be a printing issue.

        This is a day one G1 bug.

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