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https://issues.apache.org/jira/browse/HDFS-1605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12989739#comment-12989739
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dhruba borthakur commented on HDFS-1605:
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Hi todd, it will take me quite a while to get performance numbers for you. But
it is fine if you do not want this in the 0.20-append branch, no problems with
me.
> 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
>
>
> 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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