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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-2421) Improve the concurrency of SerialNumberMap in NameNode
Date Fri, 17 Aug 2012 01:56:38 GMT

     [ https://issues.apache.org/jira/browse/HDFS-2421?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Tsz Wo (Nicholas), SZE updated HDFS-2421:
-----------------------------------------

       Resolution: Fixed
    Fix Version/s:     (was: 0.24.0)
                   2.2.0-alpha
           Status: Resolved  (was: Patch Available)

I have committed this.  Thanks, Jing Zhao and Weiyan Wang!
                
> 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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