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https://issues.apache.org/jira/browse/HDFS-1774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13067198#comment-13067198
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Uma Maheswara Rao G commented on HDFS-1774:
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Hi Eli,
I am little bit confusing with the question :-(
You are talking about this line?
{code}
if (dirList.size() > 0) {
+ children = dirList.toArray(new FSDir[dirList.size()]);
}
{code}
if i am not wrong: this is because i can not assign directly list to array
right?
Since i can not guess the children size, i have chosen list initially to
collect the elements.
please correct me if i understood wrongly
> Small optimization in org.apache.hadoop.hdfs.server.datanode.FSDataset class.
> -----------------------------------------------------------------------------
>
> Key: HDFS-1774
> URL: https://issues.apache.org/jira/browse/HDFS-1774
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: data-node
> Reporter: Uma Maheswara Rao G
> Assignee: Uma Maheswara Rao G
> Fix For: 0.23.0
>
> Attachments: HDFS-1774-1.patch, HDFS-1774-1.patch, HDFS-1774.patch
>
>
> Inner class FSDir constructor is doing duplicate iterations over the listed
> files in the passed directory. We can optimize this to single loop and also
> we can avoid isDirectory check which will perform some native invocations.
> Consider a case: one directory has only one child directory and 10000
> files.
> 1) First loop will get the number of children directories.
> 2) if (numChildren > 0) , This condition will satisfy and again it will
> iterate 10001 times and also will check isDirectory.
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