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