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From "Hemanth Yamijala (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1495) Reduce locking contention on JobTracker.getTaskCompletionEvents()
Date Mon, 15 Feb 2010 15:03:28 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12833830#action_12833830

Hemanth Yamijala commented on MAPREDUCE-1495:

bq. Will try to check the possibility of using ConcurrentHashMap as it can drastically minimize
the requirement of synchronized (and by default it supports 16 concurrent threads).

Can you elaborate please ? The current data structure is a simple list. How are you modifying
this to a map ? Also, I think the ordering of events is important.

> Reduce locking contention on JobTracker.getTaskCompletionEvents()
> -----------------------------------------------------------------
>                 Key: MAPREDUCE-1495
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1495
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>    Affects Versions: 0.20.1
>            Reporter: Rajesh Balamohan
> While profiling JT for slow performance with small-jobs, it was observed that JobTracker.getTaskCompletionEvents()
is attributing to 40% of lock contention on JT.
> This JIRA ticket is created to explore the possibilities of reducing the sychronized
code block in this method. 

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