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https://issues.apache.org/jira/browse/HDFS-17777?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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William Montaz updated HDFS-17777:
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Description:
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. Another approach could be to introduce the same
asserts on namesystem lock as it seems those methods are always called in the
context of the FSNamesystem lock.
was:
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
> 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: 3.4.0, 3.3.6, 3.4.1
> Reporter: William Montaz
> Priority: Major
> 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. Another approach could be to introduce the same
> asserts on namesystem lock as it seems those methods are always called in the
> context of the FSNamesystem lock.
>
>
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