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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2080) Speed up DFS read path
Date Tue, 28 Jun 2011 20:14:18 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2080?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13056734#comment-13056734
] 

Kihwal Lee commented on HDFS-2080:
----------------------------------

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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