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  1. Hadoop Common
  2. HADOOP-3940

Reduce often attempts in memory merge with no work

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Details

    • Bug
    • Status: Closed
    • Minor
    • Resolution: Fixed
    • 0.18.0
    • 0.18.1
    • None
    • None
    • Reviewed

    Description

      ReduceTask.ReduceCopier.ShuffleRamManager initializes numRequiredMapOutputs to 0, so one of the predicates in ShuffleRamManager::waitForDataToMerge, numPendingRequests < numRequiredMapOutputs, is false until the first map output is fetched and false again after the last map output is fetched. The InMemFSMergeThread thread will loop busily in this state.

      Attachments

        1. 3940-0.patch
          0.7 kB
          Christopher Douglas
        2. 3940-1.patch
          2 kB
          Christopher Douglas

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            cdouglas Christopher Douglas
            cdouglas Christopher Douglas
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            Dates

              Created:
              Updated:
              Resolved: