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Date: Sat, 3 Mar 2012 01:27:06 +0000 (UTC)
From: "Henry Robinson (Updated) (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Updated] (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:all-tabpanel ]

Henry Robinson updated HDFS-2834:
---------------------------------

    Attachment: HDFS-2834.3.patch

Here's a patch rebased after the HA merge.
                
> 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
>         Attachments: HDFS-2834-no-common.patch, HDFS-2834.3.patch, HDFS-2834.patch, HDFS-2834.patch
>
>
> 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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