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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