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  1. JDK
  2. JDK-8076462

Preserving the referents of concurrent mark work distribution method causes long pause times

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    • gc

    Description

      During reference processing in a gc pause (in G1CollectedHeap::process_discovered_references), we need to preserve (copy) reference objects that were discovered by the concurrent marking reference processor.

      We use the G1ParPreserveCMReferentsTask GangTask for that, always executing it using all threads but then internally let some threads just do nothing if there is not enough work to do.

      The problem with that method is, if you are on a large machine with tens of threads, and there is almost nothing to do during this phase (or even during the whole GC), starting up and waiting for that many threads takes a very significant fraction of gc pause time, e.g. half of object copy time.

      A much better way would be to determine the number of required threads at the outside, and only start up as many threads as required.

      Test case: GCOld

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          duplicates

          Enhancement - null JDK-8076180 Remove space.inline.hpp from heapRegion.hpp

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Enhancement - null JDK-8076463 Add logging for the preserve CM referents task

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Enhancement - null JDK-8201492 Properly implement non-contiguous generations for Reference discovery

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved
          relates to

          Enhancement - null JDK-8076584 G1: Parallelism used for redirty logged cards needs better control

          • P2 - Crashes, loss of data, severe memory leak.
          • Open

          Enhancement - null JDK-8043575 Dynamically parallelize reference processing work

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Enhancement - null JDK-8076463 Add logging for the preserve CM referents task

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          JEP - Java Enhancement Proposal JDK-8172792 JEP 308: Improve Dynamic Number of Thread Sizing for G1

          • P3 - Major loss of function.
          • Closed

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              Unassigned Unassigned
              tschatzl Thomas Schatzl
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                Updated:
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