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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2080) Speed up DFS read path
Date Tue, 28 Jun 2011 19:06:17 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2080?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13056711#comment-13056711

Todd Lipcon commented on HDFS-2080:

I don't think your inline asm is doing quite what you want. I don't know the asm syntax well,
but it seems you're calculating the crc at data[offset], data[offset+1], and data[offset+2].
But, those have data dependencies between them. The crc32cHardware64_3parallel code calculates
three separate chunks (at 512-byte offsets from each other) pipelined together

> 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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