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Posted to mapreduce-issues@hadoop.apache.org by "Robert Joseph Evans (JIRA)" <ji...@apache.org> on 2012/06/01 18:28:23 UTC
[jira] [Created] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Robert Joseph Evans created MAPREDUCE-4301:
----------------------------------------------
Summary: Dedupe some strings in MRAM for memory savings
Key: MAPREDUCE-4301
URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
Project: Hadoop Map/Reduce
Issue Type: Improvement
Components: applicationmaster
Affects Versions: 2.0.0-alpha, 0.23.3
Reporter: Robert Joseph Evans
Assignee: Robert Joseph Evans
Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Commented] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Hudson (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13289418#comment-13289418 ]
Hudson commented on MAPREDUCE-4301:
-----------------------------------
Integrated in Hadoop-Mapreduce-trunk #1101 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1101/])
MAPREDUCE-4301. Dedupe some strings in MRAM for memory savings (bobby via tgraves) (Revision 1346002)
Result = FAILURE
tgraves : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1346002
Files :
* /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/mapreduce/split/SplitMetaInfoReader.java
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Fix For: 0.23.3
>
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Commented] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Hudson (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13288648#comment-13288648 ]
Hudson commented on MAPREDUCE-4301:
-----------------------------------
Integrated in Hadoop-Mapreduce-trunk-Commit #2335 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk-Commit/2335/])
MAPREDUCE-4301. Dedupe some strings in MRAM for memory savings (bobby via tgraves) (Revision 1346002)
Result = FAILURE
tgraves : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1346002
Files :
* /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/mapreduce/split/SplitMetaInfoReader.java
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Fix For: 0.23.3
>
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Updated] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Robert Joseph Evans (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Robert Joseph Evans updated MAPREDUCE-4301:
-------------------------------------------
Status: Patch Available (was: Open)
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 2.0.0-alpha, 0.23.3
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Commented] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Hudson (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13289372#comment-13289372 ]
Hudson commented on MAPREDUCE-4301:
-----------------------------------
Integrated in Hadoop-Hdfs-0.23-Build #278 (See [https://builds.apache.org/job/Hadoop-Hdfs-0.23-Build/278/])
merge -r 1346002:1346003 from branch-2. FIXES: MAPREDUCE-4301 (Revision 1346004)
Result = SUCCESS
tgraves : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1346004
Files :
* /hadoop/common/branches/branch-0.23/hadoop-mapreduce-project/CHANGES.txt
* /hadoop/common/branches/branch-0.23/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/split/SplitMetaInfoReader.java
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Fix For: 0.23.3
>
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Updated] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Thomas Graves (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Thomas Graves updated MAPREDUCE-4301:
-------------------------------------
Resolution: Fixed
Fix Version/s: 0.23.3
Status: Resolved (was: Patch Available)
+1 Thanks Bobby. I committed this to trunk, branch-2, and branch-23
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Fix For: 0.23.3
>
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Commented] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Hadoop QA (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287629#comment-13287629 ]
Hadoop QA commented on MAPREDUCE-4301:
--------------------------------------
-1 overall. Here are the results of testing the latest attachment
http://issues.apache.org/jira/secure/attachment/12530589/MR-4301.txt
against trunk revision .
+1 @author. The patch does not contain any @author tags.
-1 tests included. The patch doesn't appear to include any new or modified tests.
Please justify why no new tests are needed for this patch.
Also please list what manual steps were performed to verify this patch.
+1 javac. The applied patch does not increase the total number of javac compiler warnings.
+1 javadoc. The javadoc tool did not generate any warning messages.
+1 eclipse:eclipse. The patch built with eclipse:eclipse.
+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 unit tests in hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core.
+1 contrib tests. The patch passed contrib unit tests.
Test results: https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/2431//testReport/
Console output: https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/2431//console
This message is automatically generated.
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Commented] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Hudson (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13288628#comment-13288628 ]
Hudson commented on MAPREDUCE-4301:
-----------------------------------
Integrated in Hadoop-Hdfs-trunk-Commit #2389 (See [https://builds.apache.org/job/Hadoop-Hdfs-trunk-Commit/2389/])
MAPREDUCE-4301. Dedupe some strings in MRAM for memory savings (bobby via tgraves) (Revision 1346002)
Result = SUCCESS
tgraves : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1346002
Files :
* /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/mapreduce/split/SplitMetaInfoReader.java
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Fix For: 0.23.3
>
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Closed] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Arun C Murthy (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Arun C Murthy closed MAPREDUCE-4301.
------------------------------------
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Fix For: 0.23.3, 2.0.2-alpha
>
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Commented] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Hudson (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13288629#comment-13288629 ]
Hudson commented on MAPREDUCE-4301:
-----------------------------------
Integrated in Hadoop-Common-trunk-Commit #2317 (See [https://builds.apache.org/job/Hadoop-Common-trunk-Commit/2317/])
MAPREDUCE-4301. Dedupe some strings in MRAM for memory savings (bobby via tgraves) (Revision 1346002)
Result = SUCCESS
tgraves : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1346002
Files :
* /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/mapreduce/split/SplitMetaInfoReader.java
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Fix For: 0.23.3
>
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Commented] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Robert Joseph Evans (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287610#comment-13287610 ]
Robert Joseph Evans commented on MAPREDUCE-4301:
------------------------------------------------
This patch is a small safe one that only covers the JobSplit.
I looked at several other strings that also had a lot of duplicates.
TaskAttemptStatusUpdateEvent$TaskAttemptState.stateString
MapTaskAttemptImpl.diagnostics
The keys to Counters.groups
GenericGroup.displayName
The keys to GenericGroup.counters
and GenericCounter.displayName
None of the rest of these were as simple to solve because they all seem to ultimate result from either incoming RPC messages or from a parsed file. The only way to fix these is to try and dedupe them on the fly. This can be done with String.intern, but at the risk of filling up the permgen space. Or with playing games with our own internal cache.
Either of these solutions is much more risky then just a two line change so I will file a separate JIRA to explore those options.
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Updated] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Robert Joseph Evans (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Robert Joseph Evans updated MAPREDUCE-4301:
-------------------------------------------
Attachment: MR-4301.txt
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
--
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[jira] [Commented] (MAPREDUCE-4301) Dedupe some strings in MRAM for
memory savings
Posted by "Hudson (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAPREDUCE-4301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13289080#comment-13289080 ]
Hudson commented on MAPREDUCE-4301:
-----------------------------------
Integrated in Hadoop-Hdfs-trunk #1067 (See [https://builds.apache.org/job/Hadoop-Hdfs-trunk/1067/])
MAPREDUCE-4301. Dedupe some strings in MRAM for memory savings (bobby via tgraves) (Revision 1346002)
Result = SUCCESS
tgraves : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1346002
Files :
* /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/mapreduce/split/SplitMetaInfoReader.java
> Dedupe some strings in MRAM for memory savings
> ----------------------------------------------
>
> Key: MAPREDUCE-4301
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4301
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster
> Affects Versions: 0.23.3, 2.0.0-alpha
> Reporter: Robert Joseph Evans
> Assignee: Robert Joseph Evans
> Fix For: 0.23.3
>
> Attachments: MR-4301.txt
>
>
> Recently an OutOfMemoryError caused one of our jobs to become a zombie (MAPREDUCE-4300). It was a rather large job with 78000+ map tasks and only 750MB of heap configured. I took a heap dump to see if there were any obvious memory leaks, and I could not find any, but yourkit and some digging found some potential memory optimizations that we could do.
> In this particular case we could save about 20MB if SplitMetaInfoReader.readSplitMetaInfo only computed the JobSplitFile once instead of for each split. (a 2 line change)
> I will look into some others and see if there are more savings I can come up with.
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