[jira] Commented: (MAPREDUCE-64) Map-side sort is hampered by io.sort.record.percent

["Hadoop QA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-64?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12788110#action_12788110 ] 

Hadoop QA commented on MAPREDUCE-64:
------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12427438/M64-4.patch
  against trunk revision 888761.

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

    +1 tests included.  The patch appears to include 19 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 warnings.

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

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

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

Test results: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h3.grid.sp2.yahoo.net/176/testReport/
Findbugs warnings: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h3.grid.sp2.yahoo.net/176/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Checkstyle results: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h3.grid.sp2.yahoo.net/176/artifact/trunk/build/test/checkstyle-errors.html
Console output: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h3.grid.sp2.yahoo.net/176/console

This message is automatically generated.

> Map-side sort is hampered by io.sort.record.percent
> ---------------------------------------------------
>
>                 Key: MAPREDUCE-64
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-64
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Arun C Murthy
>            Assignee: Chris Douglas
>         Attachments: M64-0.patch, M64-0i.png, M64-1.patch, M64-1i.png, M64-2.patch, M64-2i.png, M64-3.patch, M64-4.patch
>
>
> Currently io.sort.record.percent is a fairly obscure, per-job configurable, expert-level parameter which controls how much accounting space is available for records in the map-side sort buffer (io.sort.mb). Typically values for io.sort.mb (100) and io.sort.record.percent (0.05) imply that we can store ~350,000 records in the buffer before necessitating a sort/combine/spill.
> However for many applications which deal with small records e.g. the world-famous wordcount and it's family this implies we can only use 5-10% of io.sort.mb i.e. (5-10M) before we spill inspite of having _much_ more memory available in the sort-buffer. The word-count for e.g. results in ~12 spills (given hdfs block size of 64M). The presence of a combiner exacerbates the problem by piling serialization/deserialization of records too...
> Sure, jobs can configure io.sort.record.percent, but it's tedious and obscure; we really can do better by getting the framework to automagically pick it by using all available memory (upto io.sort.mb) for either the data or accounting.

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