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Date: Wed, 21 Mar 2012 17:45:45 +0000 (UTC)
From: "Hudson (Commented) (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-2834) ByteBuffer-based read API for
 DFSInputStream
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    [ https://issues.apache.org/jira/browse/HDFS-2834?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13234579#comment-13234579 ] 

Hudson commented on HDFS-2834:
------------------------------

Integrated in Hadoop-Hdfs-trunk-Commit #1985 (See [https://builds.apache.org/job/Hadoop-Hdfs-trunk-Commit/1985/])
    HDFS-2834. Add a ByteBuffer-based read API to DFSInputStream. Contributed by Henry Robinson. (Revision 1303474)

     Result = SUCCESS
todd : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1303474
Files : 
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/BlockReader.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/BlockReaderLocal.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/RemoteBlockReader.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/RemoteBlockReader2.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/BlockReaderTestUtil.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestBlockReaderLocal.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestParallelRead.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestParallelReadUtil.java
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestShortCircuitLocalRead.java

                
> ByteBuffer-based read API for DFSInputStream
> --------------------------------------------
>
>                 Key: HDFS-2834
>                 URL: https://issues.apache.org/jira/browse/HDFS-2834
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Henry Robinson
>            Assignee: Henry Robinson
>             Fix For: 0.24.0
>
>         Attachments: HDFS-2834-no-common.patch, HDFS-2834.10.patch, HDFS-2834.11.patch, HDFS-2834.3.patch, HDFS-2834.4.patch, HDFS-2834.5.patch, HDFS-2834.6.patch, HDFS-2834.7.patch, HDFS-2834.8.patch, HDFS-2834.9.patch, HDFS-2834.patch, HDFS-2834.patch, hdfs-2834-libhdfs-benchmark.png
>
>
> The {{DFSInputStream}} read-path always copies bytes into a JVM-allocated {{byte[]}}. Although for many clients this is desired behaviour, in certain situations, such as native-reads through libhdfs, this imposes an extra copy penalty since the {{byte[]}} needs to be copied out again into a natively readable memory area. 
> For these cases, it would be preferable to allow the client to supply its own buffer, wrapped in a {{ByteBuffer}}, to avoid that final copy overhead. 

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