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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2421) Improve the concurrency of SerialNumberMap in NameNode
Date Fri, 17 Aug 2012 13:56:38 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13436730#comment-13436730
] 

Hudson commented on HDFS-2421:
------------------------------

Integrated in Hadoop-Mapreduce-trunk #1169 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1169/])
    HDFS-2421. Improve the concurrency of SerialNumberMap in NameNode.  Contributed by Jing
Zhao and Weiyan Wang (Revision 1374127)

     Result = FAILURE
szetszwo : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1374127
Files : 
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* /hadoop/common/trunk/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: 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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