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From "Liang Xie (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1605) Convert DFSInputStream synchronized sections to a ReadWrite lock
Date Fri, 13 Dec 2013 03:11:15 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13847100#comment-13847100
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Liang Xie commented on HDFS-1605:
---------------------------------

bq.  waitFor(4000);
totally agreed with your point, it should have a different configurable value for online app
like HBase , or offline app processing app.
I can file a minor jira for this, thanks [~stack].

> Convert DFSInputStream synchronized sections to a ReadWrite lock
> ----------------------------------------------------------------
>
>                 Key: HDFS-1605
>                 URL: https://issues.apache.org/jira/browse/HDFS-1605
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: DFSClientRWlock.1.txt, DFSClientRWlock.3.txt, HDFS-1605.txt
>
>
> Hbase does concurrent preads from multiple threads to different blocks of the same hdfs
file. Each of these pread calls invoke DFSInputStream.getFileLength() and DFSInputStream.getBlockAt().
These methods are "synchronized", thus causing all the concurrent threads to serialize. It
would help performance to convert this to a Read/Write lock



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