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Posted to common-dev@hadoop.apache.org by "Chris Douglas (JIRA)" <ji...@apache.org> on 2008/09/06 00:56:44 UTC

[jira] Updated: (HADOOP-3940) Reduce often attempts in memory merge with no work

     [ https://issues.apache.org/jira/browse/HADOOP-3940?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Chris Douglas updated HADOOP-3940:
----------------------------------

    Fix Version/s: 0.18.1

+1

Merged into 0.18 branch

> Reduce often attempts in memory merge with no work
> --------------------------------------------------
>
>                 Key: HADOOP-3940
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3940
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.18.0
>            Reporter: Chris Douglas
>            Assignee: Chris Douglas
>            Priority: Minor
>             Fix For: 0.18.1, 0.19.0
>
>         Attachments: 3940-0.patch, 3940-1.patch
>
>
> 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.

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