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https://issues.apache.org/jira/browse/HDFS-5276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13788821#comment-13788821
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Chengxiang Li commented on HDFS-5276:
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here is my test environment:
[root@node13-1 ~]# cat /proc/cpuinfo | grep name | cut -f2 -d: | uniq -c
32 Intel(R) Xeon(R) CPU E5-2690 0 @ 2.90GHz
[root@node13-1 ~]# java -version
java version "1.6.0_31"
Java(TM) SE Runtime Environment (build 1.6.0_31-b04)
Java HotSpot(TM) 64-Bit Server VM (build 20.6-b01, mixed mode)
> 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
> Attachments: DisableFSReadWriteBytesStat.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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