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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4339) Improve FsShell -du/-dus and FileSystem.getContentSummary efficiency
Date Sat, 22 Nov 2008 04:44:47 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12649897#action_12649897

Chris Douglas commented on HADOOP-4339:

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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