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From "Kai Zheng (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8901) Use ByteBuffer in striping positional read
Date Wed, 10 Aug 2016 22:13:21 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15416118#comment-15416118
] 

Kai Zheng commented on HDFS-8901:
---------------------------------

Thanks [~zhz] for the look! I thought you meant this saying in the description, right?
bq. It will also fix avoiding unnecessary data copying between striping read chunk buffers
and decode input buffers.
The above saying should be talking about the changes like the following (too long ago said,
have to think about this much):
{code}
-        chunk.copyTo(decodeInputs[i]);
+        if (chunk.useChunkBuffer()) {
+          chunk.getChunkBuffer().copyTo(decodeInputs[i]);
+        }
{code}
Note the new codes has a condition to justify the {{copyTo}} call.

> Use ByteBuffer in striping positional read
> ------------------------------------------
>
>                 Key: HDFS-8901
>                 URL: https://issues.apache.org/jira/browse/HDFS-8901
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Kai Zheng
>            Assignee: Youwei Wang
>         Attachments: HDFS-8901-v10.patch, HDFS-8901-v2.patch, HDFS-8901-v3.patch, HDFS-8901-v4.patch,
HDFS-8901-v5.patch, HDFS-8901-v6.patch, HDFS-8901-v7.patch, HDFS-8901-v8.patch, HDFS-8901-v9.patch,
HDFS-8901.v11.patch, HDFS-8901.v12.patch, HDFS-8901.v13.patch, HDFS-8901.v14.patch, initial-poc.patch
>
>
> Native erasure coder prefers to direct ByteBuffer for performance consideration. To prepare
for it, this change uses ByteBuffer through the codes in implementing striping position read.
It will also fix avoiding unnecessary data copying between striping read chunk buffers and
decode input buffers.



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