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Posted to hdfs-dev@hadoop.apache.org by "Hairong Kuang (Created) (JIRA)" <ji...@apache.org> on 2011/10/08 18:34:29 UTC

[jira] [Created] (HDFS-2421) Improve the concurrency of SerialNumberMap in NameNode

Improve the concurrency of  SerialNumberMap in NameNode
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                 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: Weiyan Wang
             Fix For: 0.24.0


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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