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https://issues.apache.org/jira/browse/HADOOP-7255?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13028162#comment-13028162
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T Jake Luciani commented on HADOOP-7255:
----------------------------------------
For simplicity this is a single node from a fresh checkout. Yes I did run this
multiple times... the stddev varies on read from 78 - 30... writes are fine in
terms of stddev.
If you build the test jar you should be able to reproduce locally.
> Performance regression bug caused by locking code
> -------------------------------------------------
>
> Key: HADOOP-7255
> URL: https://issues.apache.org/jira/browse/HADOOP-7255
> Project: Hadoop Common
> Issue Type: Bug
> Affects Versions: 0.20.203.0
> Reporter: T Jake Luciani
>
> While testing the 0.20.203 branch we have discovered quite a severe
> performance regression caused by the following checkin:
> http://svn.apache.org/viewvc?view=revision&revision=1079260
> This locking seems to cause a pause of a few seconds between tasks, example
> with DFSIOTest:
> *CURRENT CODE*
> {noformat}
> 11/05/02 21:16:28 INFO fs.TestDFSIO: ----- TestDFSIO ----- : read
> 11/05/02 21:16:28 INFO fs.TestDFSIO: Date & time: Mon May 02
> 21:16:28 EDT 2011
> 11/05/02 21:16:28 INFO fs.TestDFSIO: Number of files: 5
> 11/05/02 21:16:28 INFO fs.TestDFSIO: Total MBytes processed: 500
> 11/05/02 21:16:28 INFO fs.TestDFSIO: Throughput mb/sec: 303.3980582524272
> 11/05/02 21:16:28 INFO fs.TestDFSIO: Average IO rate mb/sec:
> 327.69122314453125
> 11/05/02 21:16:28 INFO fs.TestDFSIO: IO rate std deviation: 78.95767116969083
> 11/05/02 21:16:28 INFO fs.TestDFSIO: Test exec time sec: 19.476
> 11/05/02 21:16:28 INFO fs.TestDFSIO:
> {noformat}
> *WITH PATCH REMOVED*
> {noformat}
> 11/05/02 21:19:03 INFO fs.TestDFSIO: ----- TestDFSIO ----- : read
> 11/05/02 21:19:03 INFO fs.TestDFSIO: Date & time: Mon May 02
> 21:19:03 EDT 2011
> 11/05/02 21:19:03 INFO fs.TestDFSIO: Number of files: 5
> 11/05/02 21:19:03 INFO fs.TestDFSIO: Total MBytes processed: 500
> 11/05/02 21:19:03 INFO fs.TestDFSIO: Throughput mb/sec:
> 366.03221083455344
> 11/05/02 21:19:03 INFO fs.TestDFSIO: Average IO rate mb/sec:
> 366.35528564453125
> 11/05/02 21:19:03 INFO fs.TestDFSIO: IO rate std deviation:
> 11.020931463080379
> 11/05/02 21:19:03 INFO fs.TestDFSIO: Test exec time sec: 3.543
> 11/05/02 21:19:03 INFO fs.TestDFSIO:
> {noformat}
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