[
https://issues.apache.org/jira/browse/MAPREDUCE-5821?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13998219#comment-13998219
]
Hudson commented on MAPREDUCE-5821:
-----------------------------------
FAILURE: Integrated in Hadoop-Hdfs-trunk #1753 (See
[https://builds.apache.org/job/Hadoop-Hdfs-trunk/1753/])
MAPREDUCE-5821. Avoid unintentional reallocation of byte arrays in segments
during merge. Contributed by Todd Lipcon (cdouglas:
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1594654)
* /hadoop/common/trunk/hadoop-mapreduce-project/CHANGES.txt
*
/hadoop/common/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/Merger.java
> IFile merge allocates new byte array for every value
> ----------------------------------------------------
>
> Key: MAPREDUCE-5821
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5821
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: performance, task
> Affects Versions: 2.4.1
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: 3.0.0, 2.5.0, 2.4.1
>
> Attachments: after-patch.png, before-patch.png, mapreduce-5821.txt,
> mapreduce-5821.txt
>
>
> I wrote a standalone benchmark of the MapOutputBuffer and found that it did a
> lot of allocations during the merge phase. After looking at an allocation
> profile, I found that IFile.Reader.nextRawValue() would always allocate a new
> byte array for every value, so the allocation rate goes way up during the
> merge phase of the mapper. I imagine this also affects the reducer input,
> though I didn't profile that.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
