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https://issues.apache.org/jira/browse/HDFS-1110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12862783#action_12862783
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Eli Collins commented on HDFS-1110:
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Won't this require a lot of synchronization that previously didn't exist? ie
every time you delete a file you'll need to atomically decrement the count in
the map and possibly mutate the map to remove the file. Would be nice if
different parts of the namespace didn't require synchronization because they
happened to share files with the same name.
> Namenode heap optimization - reuse objects for commonly used file names
> -----------------------------------------------------------------------
>
> Key: HDFS-1110
> URL: https://issues.apache.org/jira/browse/HDFS-1110
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Suresh Srinivas
> Assignee: Suresh Srinivas
> Fix For: 0.22.0
>
> Attachments: hdfs-1110.2.patch, hdfs-1110.patch
>
>
> There are a lot of common file names used in HDFS, mainly created by
> mapreduce, such as file names starting with "part". Reusing byte[]
> corresponding to these recurring file names will save significant heap space
> used for storing the file names in millions of INodeFile objects.
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