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From "Hadoop QA (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2834) ByteBuffer-based read API for DFSInputStream
Date Mon, 05 Mar 2012 08:36:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2834?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13222221#comment-13222221
] 

Hadoop QA commented on HDFS-2834:
---------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12517054/hdfs-2834-libhdfs-benchmark.png
  against trunk revision .

    +1 @author.  The patch does not contain any @author tags.

    -1 tests included.  The patch doesn't appear to include any new or modified tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    -1 patch.  The patch command could not apply the patch.

Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/1949//console

This message is automatically generated.
                
> 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-2834.4.patch,
HDFS-2834.5.patch, HDFS-2834.6.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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