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https://issues.apache.org/jira/browse/HADOOP-6502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13207544#comment-13207544
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Hadoop QA commented on HADOOP-6502:
-----------------------------------
-1 overall. Here are the results of testing the latest attachment
http://issues.apache.org/jira/secure/attachment/12514444/hadoop-6502-trunk.txt
against trunk revision .
+1 @author. The patch does not contain any @author tags.
-1 tests included. The patch doesn't appear to include any new or modified
tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
+1 javadoc. The javadoc tool did not generate any warning messages.
+1 javac. The applied patch does not increase the total number of javac
compiler warnings.
+1 eclipse:eclipse. The patch built with eclipse:eclipse.
+1 findbugs. The patch does not introduce any new Findbugs (version 1.3.9)
warnings.
+1 release audit. The applied patch does not increase the total number of
release audit warnings.
+1 core tests. The patch passed unit tests in .
+1 contrib tests. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-HADOOP-Build/595//testReport/
Console output:
https://builds.apache.org/job/PreCommit-HADOOP-Build/595//console
This message is automatically generated.
> DistributedFileSystem#listStatus is very slow when listing a directory with a
> size of 1300
> ------------------------------------------------------------------------------------------
>
> Key: HADOOP-6502
> URL: https://issues.apache.org/jira/browse/HADOOP-6502
> Project: Hadoop Common
> Issue Type: Bug
> Components: util
> Affects Versions: 0.20.0
> Reporter: Hairong Kuang
> Assignee: Todd Lipcon
> Priority: Critical
> Attachments: 6502.patch, 6502_v2.patch, hadoop-6502-trunk.txt,
> hadoop-6502-trunk.txt
>
>
> When listing a directory of around 1300 children, it takes hundreds of
> milliseconds. It turns out the slowdowness is caused by the change made by
> HADOOP-4187. The return value of listStatus is an array of FileStatus. When
> deserializing each element of the array,
> ReflectionUtils#newInstance(Class<T>, Configuration) is called and then calls
> setConf, which calls setJobConf. SetJobConf checks if JobConf is on the class
> path by calling Configuration#getClassByName. Even though
> Configuration#getClassByName tries to optimize the lookup using a cached map,
> but since JobConf is not in the class path, so it is not in the cache. Every
> checkup ends up calling Class.ForName which is very expensive. Deserializing
> an array of 1300 entries requires calling of Class#ForName 1300 times!
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