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  1. JDK
  2. JDK-8152438

Threads may do significant work out of the non-shared overflow buffer

    Details

    • Subcomponent:
      gc
    • Resolved In Build:
      b127

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        Description

        Some task queue statistics measurements on BigRamTester (attached) indicate that particularly during mixed gcs a significant part of the gc threads operate out of the local overflow buffer, and in many cases also do so while the shared task queue is not completely full or even completely empty, disallowing other threads to steal and distribute work.

        BigRamTester run options -Xlog:gc*=debug,gc+phases+task=trace,gc+task+stats=trace,gc+refine=info:x.log -Xms20G -Xmx20G BigRamTester on a 2x10x2 machine.

        Look at the attached log file for the task queue stats, particularly the new columns snotfull (indicating that we popped from the overflow queue while the shared queue has not been full) and sempty (indicating that we popped from the overflow queue while shared queue has been empty).

        Relevant patches attached.

          Attachments

          1. 8152438-fix-push-overflow-into-shared-first
            2 kB
          2. BigRamTester.java
            7 kB
          3. enable-taskqueue-stats
            0.5 kB
          4. improved-taskqueue-stats
            2 kB
          5. x.log
            584 kB

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