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From "Chengxiang Li (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-5276) FileSystem.Statistics got performance issue on multi-thread read/write.
Date Mon, 30 Sep 2013 03:15:24 GMT

     [ https://issues.apache.org/jira/browse/HDFS-5276?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chengxiang Li updated HDFS-5276:
--------------------------------

    Attachment: jstack-trace.PNG
                hdfs-test.PNG
                HDFSStatisticTest.java

i write a simple test case, run it on a (4 node, each 32 core) cluster, which reproduce this
issue.

> 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: HDFSStatisticTest.java, hdfs-test.PNG, jstack-trace.PNG
>
>
> 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 test profile,
32 threads read data from HDFS, about 70% cpu time is spent on FileSystem.Statistics.incrementBytesRead().



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