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  1. JDK
  2. JDK-8077945

Incorrect or inaccurate logging for G1 GC

    Details

    • Type: Bug
    • Status: Closed
    • Priority: P5
    • Resolution: Not an Issue
    • Affects Version/s: 8u40
    • Fix Version/s: 10
    • Component/s: hotspot
    • Labels:
    • Subcomponent:
      gc
    • CPU:
      x86
    • OS:
      linux_2.6

      Description

      The suspicion is that G1 GC logging is partly incorrect and/or inaccurate
      The attached gc.log file contains the command line args at the top.

      1. Line 134:
         [Eden: 2456.0M(2456.0M)->0.0B(2200.0M) Survivors: 0.0B->256.0M Heap: 2456.0M(24.0G)->249.9M(24.0G)]

      The survivors contain 256.0m while the total heap contains 249.9m.
      This is inaccurate at best.

      2. Line 7500
         [Eden: 3568.0M(3568.0M)->0.0B(3216.0M) Survivors: 112.0M->464.0M Heap: 11.3G(24.0G)->8694.0M(24.0G)]

      My understanding is that eden is now 3216.0M. When looking at the subsequent
      collection at line 7652 the size of eden is now 1992m containing 2520m which means
      it's 127% full .This is clearly wrong :

         [Eden: 2520.0M(1992.0M)->0.0B(2144.0M) Survivors: 464.0M->312.0M Heap: 11.0G(24.0G)->10236.0M(24.0G)]


      If the eden was resized somewhere between the collections at 7500 and 7652 this should be logged.
      1. gc.log.gz
        9.32 MB
        Thomas Viessmann

        Issue Links

          Activity

          Hide
          tviessma Thomas Viessmann (Inactive) added a comment -
          GC logfile
          Show
          tviessma Thomas Viessmann (Inactive) added a comment - GC logfile
          Hide
          jwilhelm Jesper Wilhelmsson added a comment -
          ILW = Low (bad number in log), Low (haven't seen it before), High (none) = P5
          Show
          jwilhelm Jesper Wilhelmsson added a comment - ILW = Low (bad number in log), Low (haven't seen it before), High (none) = P5
          Hide
          ehelin Erik Helin added a comment -
          This is no longer an issue after unified logging. The unified logging implementation will print the change in regions for eden, survivor and old and the change in megabytes for the overall heap usage.
          Show
          ehelin Erik Helin added a comment - This is no longer an issue after unified logging. The unified logging implementation will print the change in regions for eden, survivor and old and the change in megabytes for the overall heap usage.

            People

            • Assignee:
              Unassigned
              Reporter:
              tviessma Thomas Viessmann (Inactive)
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              Watchers:
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              Dates

              • Created:
                Updated:
                Resolved: