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