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Posted to hdfs-dev@hadoop.apache.org by "William Montaz (Jira)" <ji...@apache.org> on 2025/04/30 12:34:00 UTC

[jira] [Created] (HDFS-17777) Improve ExcessRedundancyMap locking semantics

William Montaz created HDFS-17777:
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             Summary: Improve ExcessRedundancyMap locking semantics
                 Key: HDFS-17777
                 URL: https://issues.apache.org/jira/browse/HDFS-17777
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: namenode
    Affects Versions: 3.4.1, 3.3.6, 3.4.0
            Reporter: William Montaz
         Attachments: Capture d’écran 2025-04-30 à 14.32.41.png

ExcessRedundancyMap uses synchronized keyword for threadsafety. However prior to introduce this class, the operations such as contains were made without a new lock, they were called inside BlockManager with verification that the fsNamesystem lock was held in read or write mode depending on the situation.
 
ExcessRedundancyMap now forces all thread to grab the same exclusive lock, even if in general a lot more read are performed on the class.
 
By using a ReentrantReadWriteLock for ExcessRedundancyMap we could improve throughput of the namenode
 
 



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