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https://issues.apache.org/jira/browse/HDFS-2080?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13056734#comment-13056734
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Kihwal Lee commented on HDFS-2080:
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It's one the indirect addressing mode. For example, (%rax,%rdi,2) means
memory[rax + rdi*2].
So if the chunks in the buffer back to back, three chunks will get processed
with rdi being the size of chunk. It can be made to access three independent
memory locations with a bit of performance loss.
> Speed up DFS read path
> ----------------------
>
> Key: HDFS-2080
> URL: https://issues.apache.org/jira/browse/HDFS-2080
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs client
> Affects Versions: 0.23.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: 0.23.0
>
> Attachments: hdfs-2080.txt, hdfs-2080.txt
>
>
> I've developed a series of patches that speeds up the HDFS read path by a
> factor of about 2.5x (~300M/sec to ~800M/sec for localhost reading from
> buffer cache) and also will make it easier to allow for advanced users (eg
> hbase) to skip a buffer copy.
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