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From "Charles Lamb (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7435) PB encoding of block reports is very inefficient
Date Tue, 03 Mar 2015 16:44:06 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14345311#comment-14345311
] 

Charles Lamb commented on HDFS-7435:
------------------------------------

Hi @daryn,

The new patch looks pretty good to me. Just a few nits.

FsDatasetImpl still has one line that exceeds the 80 chars, and there are a couple of unused
imports in the new test TestBlockListAsLongs. Also in that test, IWBNI you could use the specific
Mockito static imports that are needed rather than the * import.


> 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
>         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
>
>
> 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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