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Date: Sat, 18 Aug 2012 06:59:38 +1100 (NCT)
From: "Daryn Sharp (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Updated] (HDFS-2421) Improve the concurrency of
  SerialNumberMap in NameNode
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     [ https://issues.apache.org/jira/browse/HDFS-2421?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Daryn Sharp updated HDFS-2421:
------------------------------

    Fix Version/s: 0.23.3

Merged to branch 23.
                
> 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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