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Date: Fri, 13 Dec 2013 04:31:10 +0000 (UTC)
From: "Liang Xie (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12497152.1296374682985.30398.1386909070576@arcas>
In-Reply-To: <JIRA.12497152.1296374682985@arcas>
References: <JIRA.12497152.1296374682985@arcas>
Subject: [jira] [Commented] (HDFS-1605) Convert DFSInputStream synchronized
 sections to a ReadWrite lock
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    [ https://issues.apache.org/jira/browse/HDFS-1605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13847152#comment-13847152 ] 

Liang Xie commented on HDFS-1605:
---------------------------------

bq. We should write a test to demonstrate the improvement. I can do that unless you have one around the place?
I think it's still too early to do it. We need to fix another hotspot about BlockReaderLocal as well, just filed HDFS-5664 FYI.

> 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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