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https://issues.apache.org/jira/browse/HDFS-1093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12860834#action_12860834
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dhruba borthakur commented on HDFS-1093:
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A typical analysis of the workload in our cluster shows that the following
types of RPC are processed by the namenode:
listStatus 47%
openfiles 42%
createfiles 3%
mkdirs 3%
rename 2%
deletefiles 1%
> Improve namenode scalability by splitting the FSNamesystem synchronized
> section in a read/write lock
> ----------------------------------------------------------------------------------------------------
>
> Key: HDFS-1093
> URL: https://issues.apache.org/jira/browse/HDFS-1093
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: name-node
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: NNreadwriteLock.txt
>
>
> Most critical data structures in the NameNode (NN) are protected by a
> syncronized methods in the FSNamesystem class. This essentially makes
> critical code paths in the NN single-threaded. However, a large percentage of
> the NN calls are listStatus, getBlockLocations, etc which do not change
> internal data structures at all, these are read-only calls. If we change the
> FSNamesystem lock to a read/write lock, many of the above operations can
> occur in parallel, thus improving the scalability of the NN.
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