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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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Attachment: HDFS-2834.8.patch
This patch should fix the findbugs warning, plus removes some debugging output.
It also includes changes per Todd's review.
I ran TestParallelLocalRead for a couple of hours with no failures - I'll try
for a longer run tonight.
I also benchmarked with and without the closure objects in DFSInputStream.
There's no significant difference in throughput, even for small reads (I
measured with 32 bytes reads).
> 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-2834.7.patch,
> HDFS-2834.8.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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