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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-3427) In ReduceTask::fetchOutputs, wait for result can be improved slightly
Date Thu, 22 May 2008 07:03:55 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-3427?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Devaraj Das updated HADOOP-3427:

    Attachment: 3427.patch

This patch mainly introduces this change - Defines a number to indicate when the shuffle scheduler
should stop and just wait for notifications from the fetchers. This number is hardcoded to
(4 * numCopiers). 

> In ReduceTask::fetchOutputs, wait for result can be improved slightly
> ---------------------------------------------------------------------
>                 Key: HADOOP-3427
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3427
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Devaraj Das
>            Assignee: Devaraj Das
>             Fix For: 0.18.0
>         Attachments: 3427.patch
> The getCopyResult call in ReduceTask::fetchOutputs waits for 2 seconds if the results
list is empty. This can be improved to wait only when sufficient number of fetches (above
a certain threshold) have been scheduled. The threshold should ensure that all the fetcher
threads would be busy enough, and in this case, the call to getCopyResult would return only
when a fetcher thread wakes it up.

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