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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-2047) reduce overhead of findSpeculativeTask
Date Sun, 27 Feb 2011 22:00:38 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2047?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13000050#comment-13000050
] 

Hadoop QA commented on MAPREDUCE-2047:
--------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12457218/2047.3.patch
  against trunk revision 1074251.

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 3 new or modified tests.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 1.3.9) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit
warnings.

    +1 core tests.  The patch passed core unit tests.

    -1 contrib tests.  The patch failed contrib unit tests.

    +1 system test framework.  The patch passed system test framework compile.

Test results: https://hudson.apache.org/hudson/job/PreCommit-MAPREDUCE-Build/68//testReport/
Findbugs warnings: https://hudson.apache.org/hudson/job/PreCommit-MAPREDUCE-Build/68//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: https://hudson.apache.org/hudson/job/PreCommit-MAPREDUCE-Build/68//console

This message is automatically generated.

> reduce overhead of findSpeculativeTask
> --------------------------------------
>
>                 Key: MAPREDUCE-2047
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2047
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobtracker
>         Environment: hadoop-20 with HADOOP-2141
>            Reporter: Joydeep Sen Sarma
>            Assignee: Joydeep Sen Sarma
>         Attachments: 2047.3.patch, mapreduce-2047.1.patch, mapreduce-2047.2.patch
>
>
> We are bottlenecked (in the JT) on the jobtracker lock and calls to findSpeculativeTask
frequently show up as one of the top routines (by time) called holding this lock.
> this routine calls canBeSpeculated() and hasRunOnMachine() for each task in a candidate
job. Both these routines are reasonably expensive when invoked repeatedly  for thousands of
tasks. The top candidates for speculation from a job only need to be refreshed periodically
(and not once every heartbeat) - and we can can avoid most of these invocations this way.

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