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https://issues.apache.org/jira/browse/HDFS-2834?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Henry Robinson updated HDFS-2834:
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Description:
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.
was:
The {{DFSClient}} 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.
Summary: ByteBuffer-based read API for DFSInputStream (was:
ByteBuffer-based read API for DFSClient)
> 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
>
> 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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