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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1719) Improve the utilization of shuffle copier threads
Date Wed, 29 Aug 2007 21:22:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1719?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12523683
] 

Doug Cutting commented on HADOOP-1719:
--------------------------------------

Have you benchmarked this at all yet?

> Improve the utilization of shuffle copier threads
> -------------------------------------------------
>
>                 Key: HADOOP-1719
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1719
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Devaraj Das
>            Assignee: Devaraj Das
>             Fix For: 0.15.0
>
>         Attachments: 1719.1.patch, 1719.patch
>
>
> In the current design, the scheduling of copies is done and the scheduler (the main loop
in fetchOutputs) won't schedule anything until it hears back from at least one of the copier
threads. Due to this, the main loop won't query the TaskTracker asking for new map locations
and may not be using all the copiers effectively. This may not be an issue for small-sized
map outputs, where at steady state, the frequency of such notifications is frequent.
> Ideally, we should schedule all what we can, and, depending on how busy we currently
are, query the tasktracker for more map locations.

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