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From "Liang Xie (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6591) while loop is executed tens of thousands of times in Hedged Read
Date Sat, 28 Jun 2014 14:55:24 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14046875#comment-14046875

Liang Xie commented on HDFS-6591:

[~andrew.purtell@gmail.com], good idea!
[~cnauroth], will dive into it definitely, nice finding! so that memory copy optimization
is immature ? :) i will rethink it later. (I assumed even two threads mutate the buffer in
a face condition, the final result should be same due to that two threads have read out a
same source result.)

> while loop is executed tens of thousands of times  in Hedged  Read
> ------------------------------------------------------------------
>                 Key: HDFS-6591
>                 URL: https://issues.apache.org/jira/browse/HDFS-6591
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>    Affects Versions: 2.4.0
>            Reporter: LiuLei
>            Assignee: Liang Xie
>         Attachments: HDFS-6591-v2.txt, HDFS-6591-v3.txt, HDFS-6591.txt, LoopTooManyTimesTestCase.patch
> I download hadoop-2.4.1-rc1 code from http://people.apache.org/~acmurthy/hadoop-2.4.1-rc1/,
 I test the  Hedged  Read. I find the while loop in hedgedFetchBlockByteRange method is executed
tens of thousands of times.

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