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https://issues.apache.org/jira/browse/HADOOP-4339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12649897#action_12649897
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Chris Douglas commented on HADOOP-4339:
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In FsShell, it makes more sense to save the length instead of the
ContentSummary. The FileSystem change looks good.
> Improve FsShell -du/-dus and FileSystem.getContentSummary efficiency
> --------------------------------------------------------------------
>
> Key: HADOOP-4339
> URL: https://issues.apache.org/jira/browse/HADOOP-4339
> Project: Hadoop Core
> Issue Type: Bug
> Components: fs
> Affects Versions: 0.18.1
> Reporter: David Phillips
> Attachments: hadoop-fsshell-du-simple.patch
>
>
> FsShell.du has two inefficiencies:
> * calling getContentSummary twice for each top-level item rather than calling
> it once and saving the result
> * calling getContentSummary for files rather than using the size it already
> has in FileStatus
> getContentSummary has one:
> * calling itself for files rather than using the length it already has in
> FileStatus
> Every call to getContentSummary results in a call to getFileStatus, which may
> be expensive (e.g. NativeS3FileSystem has both network latency and actual
> monetary cost).
> The simple solution:
> * FsShell.du calls once per item and saves the ContentSummary
> * FsShell.du uses FileStatus.getLen for files
> * getContentSummary only calls itself for directories
> Another solution, rather than adding special casing to callers, is to add a
> getContentSummary that takes a FileStatus.
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