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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5276) FileSystem.Statistics got performance issue on multi-thread read/write.
Date Tue, 15 Oct 2013 01:09:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13794744#comment-13794744
] 

Andrew Wang commented on HDFS-5276:
-----------------------------------

Cool, that all works for me. +1 on the new patch; maybe wait a bit in case anyone else wants
to ring in, but I think it's fine to commit now if you want.

> 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,
HDFS-5276.003.patch, HDFSStatisticTest.java, hdfs-test.PNG, jstack-trace.PNG, TestFileSystemStatistics.java,
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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