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https://issues.apache.org/jira/browse/HDFS-5276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13792641#comment-13792641
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Hudson commented on HDFS-5276:
------------------------------
FAILURE: Integrated in Hadoop-Mapreduce-trunk #1575 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1575/])
Move HDFS-5276 to 2.3.0 in CHANGES.txt (llu:
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1531228)
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
HDFS-5276. Remove volatile from LightWeightHashSet. (Junping Du via llu) (llu:
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1531225)
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
*
/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/LightWeightHashSet.java
> FileSystem.Statistics got performance issue on multi-thread read/write.
> -----------------------------------------------------------------------
>
> Key: HDFS-5276
> URL: https://issues.apache.org/jira/browse/HDFS-5276
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.0.4-alpha
> Reporter: Chengxiang Li
> Assignee: Colin Patrick McCabe
> Attachments: DisableFSReadWriteBytesStat.patch, HDFS-5276.001.patch,
> HDFS-5276.002.patch, HDFSStatisticTest.java, hdfs-test.PNG, jstack-trace.PNG,
> ThreadLocalStat.patch
>
>
> FileSystem.Statistics is a singleton variable for each FS scheme, each
> read/write on HDFS would lead to a AutomicLong.getAndAdd(). AutomicLong does
> not perform well in multi-threads(let's say more than 30 threads). so it may
> cause serious performance issue. during our spark test profile, 32 threads
> read data from HDFS, about 70% cpu time is spent on
> FileSystem.Statistics.incrementBytesRead().
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