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https://issues.apache.org/jira/browse/HDFS-14865?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16937757#comment-16937757
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David Mollitor commented on HDFS-14865:
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[~elgoiri]
So, I was looking at the code, looking to remove some synchronization wherever
I can find.
In this case, the threads require the {{namesystem}} write lock to interact
with methods that modify the internal structure, so that is a pretty
restrictive access applied. On top of it, I did not remove synchronization
from the class per se, I simply pushed it down into the collection using a
{{ConcurrentHashMap}}. The {{ConcurrentHashMap}} is nifty because it
internally has several locks so that it can lock certain sections of the
{{Map}} without locking the entire structure.
My aim here is to make it possible for the {{get*()}} methods of this class to
be able to interact with the structure without serialized synchronization.
> Reduce Synchronization in DatanodeManager
> -----------------------------------------
>
> Key: HDFS-14865
> URL: https://issues.apache.org/jira/browse/HDFS-14865
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 3.2.0
> Reporter: David Mollitor
> Assignee: David Mollitor
> Priority: Major
> Attachments: HDFS-14865.1.patch, HDFS-14865.2.patch,
> HDFS-14865.3.patch
>
>
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