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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7435) PB encoding of block reports is very inefficient
Date Mon, 30 Nov 2015 15:17:11 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15031939#comment-15031939
] 

Daryn Sharp commented on HDFS-7435:
-----------------------------------

[~liuml07], good catch!  Not sure how I accidentally did that and I don't know why the test
still passes.  I think your proposed fix is correct.  I know extremely little of the benchmark
tool so I'd be unable to add a test (for the test!) in a timely manner, so if you'd like the
credit for the bug then I'm fine with you doing the jira.

> PB encoding of block reports is very inefficient
> ------------------------------------------------
>
>                 Key: HDFS-7435
>                 URL: https://issues.apache.org/jira/browse/HDFS-7435
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode, namenode
>    Affects Versions: 2.0.0-alpha, 3.0.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Critical
>             Fix For: 2.7.0
>
>         Attachments: HDFS-7435.000.patch, HDFS-7435.001.patch, HDFS-7435.002.patch, HDFS-7435.patch,
HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch,
HDFS-7435.patch, HDFS-7435.patch
>
>
> Block reports are encoded as a PB repeating long.  Repeating fields use an {{ArrayList}}
with default capacity of 10.  A block report containing tens or hundreds of thousand of longs
(3 for each replica) is extremely expensive since the {{ArrayList}} must realloc many times.
 Also, decoding repeating fields will box the primitive longs which must then be unboxed.



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