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From "Todd Lipcon (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-2834) ByteBuffer-based read API for DFSInputStream
Date Wed, 21 Mar 2012 17:31:41 GMT

     [ https://issues.apache.org/jira/browse/HDFS-2834?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Todd Lipcon updated HDFS-2834:

       Resolution: Fixed
    Fix Version/s: 0.24.0
     Hadoop Flags: Reviewed
           Status: Resolved  (was: Patch Available)

+1. Committed to trunk. Thanks for the nice contribution, Henry! Let me know when you have
the libhdfs portion ready and I will take a look.
> 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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