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Posted to common-dev@hadoop.apache.org by "Chris Douglas (JIRA)" <ji...@apache.org> on 2009/04/13 23:58:14 UTC

[jira] Commented: (HADOOP-5664) Use of ReentrantLock.lock() in MapOutputBuffer takes up too much cpu time

    [ https://issues.apache.org/jira/browse/HADOOP-5664?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12698565#action_12698565 ] 

Chris Douglas commented on HADOOP-5664:
---------------------------------------

That does seem high, though I haven't seen comparable results for any mappers I've profiled. What is your map doing? Do your keys/values serialize using a series of small writes? Which JVM are you running?

> Use of ReentrantLock.lock() in MapOutputBuffer takes up too much cpu time
> -------------------------------------------------------------------------
>
>                 Key: HADOOP-5664
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5664
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.19.1
>            Reporter: Bryan Duxbury
>            Priority: Minor
>
> In examining a profile of one of my mappers today, I noticed that the method ReentrantLock.lock() in MapTask$MapOutputBuffer seems to be taking up ~11 seconds out of around 100 seconds total. It seems like 10% is an awfully large amount of time to spend in this lock. 

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