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https://issues.apache.org/jira/browse/HDFS-2421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13437300#comment-13437300
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Hudson commented on HDFS-2421:
------------------------------
Integrated in Hadoop-Hdfs-0.23-Build #347 (See
[https://builds.apache.org/job/Hadoop-Hdfs-0.23-Build/347/])
svn merge -c 1374127. FIXES: HDFS-2421. Improve the concurrency of
SerialNumberMap in NameNode. Contributed by Jing Zhao and Weiyan Wang
(Revision 1374417)
Result = SUCCESS
daryn : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1374417
Files :
*
/hadoop/common/branches/branch-0.23/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
*
/hadoop/common/branches/branch-0.23/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/SerialNumberManager.java
> Improve the concurrency of SerialNumberMap in NameNode
> -------------------------------------------------------
>
> Key: HDFS-2421
> URL: https://issues.apache.org/jira/browse/HDFS-2421
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: name-node
> Reporter: Hairong Kuang
> Assignee: Jing Zhao
> Fix For: 0.23.3, 2.2.0-alpha
>
> Attachments: HDFS-2421.patch, performance_100000_op.png,
> performance_10000_op.png, performance_SerialNumberManager.png,
> TestSerialNumberManager.java
>
>
> After enabled permission checking in our HDFS test cluster, our benchmark
> observed a significant reduced concurrency in NameNode. Investigation showed
> that most threads were blocked at acquiring the lock of
> org.apache.hadoop.hdfs.server.namenode.SerialNumberManager$SerialNumberMap.
> We used concurrentHashMap to replace Hashmap + synchronized methods, which
> greatly improved the situation.
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