[jira] Commented: (HDFS-1558) Optimize FSNamesystem.startFileInternal

["Lianhui Wang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-1558?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12983763#action_12983763 ] 

Lianhui Wang commented on HDFS-1558:
------------------------------------

that is happen in many methods.for example;
getListing()
getFileInfo()
....
in the getListing() it has dir.isDir(src), checkPathAccess(), checkTraverse(),dir.getListing().
all of them call the normalizePath(src), and in the end they call :byte[][] getPathComponents(String path). 
i think after NN receive the string in the rpc method, it can change the byte[][].

> Optimize FSNamesystem.startFileInternal
> ---------------------------------------
>
>                 Key: HDFS-1558
>                 URL: https://issues.apache.org/jira/browse/HDFS-1558
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Dmytro Molkov
>            Assignee: Dmytro Molkov
>            Priority: Minor
>             Fix For: 0.23.0
>
>
> Currently on file creation inside of FSNamesystem.startFileInternal there are three calls to FSDirectory that are essentially the same:
> dir.exists(src)
> dir.isDir(src)
> dir.getFileInode(src)
> All of them have to fetch the inode and then do some processing on it.
> If instead we were to fetch the inode once and then do all of the processing on this INode object it would save us two trips through the namespace + 2 calls to normalizePath all of which are relatively expensive.

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