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https://issues.apache.org/jira/browse/HDFS-13947?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16634368#comment-16634368
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BELUGA BEHR commented on HDFS-13947:
------------------------------------

[~elgoiri] Thanks for the review!

{{DFS_DATANODE_DIRECTORYSCAN_THROTTLE_LIMIT_MS_PER_SEC_DEFAULT}} was previously 
1000.  1000 indicated that the class should be unthrottled, which is confusing 
to say the least.  I've simply changed it here so that a value less than 0 
(default: -1) indicates unthrottled.

{code:java|title=DirectoryScanner.java}
    // with a default of '1000', the throttling is skipped
    if ((throttleLimitMsPerSec < 1000) &&
          (throttleTimer.now(TimeUnit.MILLISECONDS) > throttleLimitMsPerSec)) {

        Thread.sleep(MILLIS_PER_SECOND - throttleLimitMsPerSec);
        throttleTimer.reset().start();
      }
{code}

> Review of DirectoryScanner Class
> --------------------------------
>
>                 Key: HDFS-13947
>                 URL: https://issues.apache.org/jira/browse/HDFS-13947
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>    Affects Versions: 3.2.0
>            Reporter: BELUGA BEHR
>            Assignee: BELUGA BEHR
>            Priority: Major
>         Attachments: HDFS-13947.1.patch, HDFS-13947.2.patch
>
>
> Review of Directory Scanner.   Replaced a lot of code with Guava MultiMap.  
> Some general house cleaning and improved logging.  For performance, using 
> {{ArrayList}} instead of {{LinkedList}} where possible, especially since 
> these lists can be quite large a LinkedList will consume a lot of memory and 
> be slow to sort/iterate over.
> https://stackoverflow.com/questions/322715/when-to-use-linkedlist-over-arraylist-in-java



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