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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7433) DatanodeManager#datanodeMap should be a HashMap, not a TreeMap, to optimize lookup performance
Date Thu, 15 Jan 2015 16:53:35 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7433?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14278933#comment-14278933
] 

Ming Ma commented on HDFS-7433:
-------------------------------

Daryn, I agree with you, there is no need to complicate things to address this minor issue.
Maybe we can add some comments in the code to explain this? Otherwise, the patch LGTM.

> DatanodeManager#datanodeMap should be a HashMap, not a TreeMap, to optimize lookup performance
> ----------------------------------------------------------------------------------------------
>
>                 Key: HDFS-7433
>                 URL: https://issues.apache.org/jira/browse/HDFS-7433
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>    Affects Versions: 2.0.0-alpha, 3.0.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Critical
>         Attachments: HDFS-7433.patch, HDFS-7433.patch
>
>
> The datanode map is currently a {{TreeMap}}.  For many thousands of datanodes, tree lookups
are ~10X more expensive than a {{HashMap}}.  Insertions and removals are up to 100X more expensive.



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