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From "Hairong Kuang (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-2421) Improve the concurrency of SerialNumberMap in NameNode
Date Sat, 08 Oct 2011 16:34:29 GMT
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: 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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