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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5664) Use of ReentrantLock.lock() in MapOutputBuffer takes up too much cpu time
Date Thu, 28 May 2009 22:57:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5664?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12714211#action_12714211
] 

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

Re-ran test-patch:
{noformat}
     [exec] -1 overall.
     [exec]
     [exec]     +1 @author.  The patch does not contain any @author tags.
     [exec]
     [exec]     -1 tests included.  The patch doesn't appear to include any new or modified
tests.
     [exec]                         Please justify why no tests are needed for this patch.
     [exec]
     [exec]     +1 javadoc.  The javadoc tool did not generate any warning messages.
     [exec]
     [exec]     +1 javac.  The applied patch does not increase the total number of javac compiler
warnings.
     [exec]
     [exec]     +1 findbugs.  The patch does not introduce any new Findbugs warnings.
     [exec]
     [exec]     +1 Eclipse classpath. The patch retains Eclipse classpath integrity.
     [exec]
     [exec]     +1 release audit.  The applied patch does not increase the total number of
release audit warnings.
{noformat}

All the mapred tests pass. The test that failed in the original Hudson run was not related.

> 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
>            Assignee: Chris Douglas
>            Priority: Minor
>         Attachments: 5664-0.patch, 5664-1.patch
>
>
> 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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