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https://issues.apache.org/jira/browse/HADOOP-7401?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tsz Wo (Nicholas), SZE reassigned HADOOP-7401:
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Assignee: monica beckwith
Hi Monica, this is an interesting discovery! Could you also post the results
before and after the patch?
BTW, you need to generate patches at the project root directory. Otherwise,
Hadoop QA could not apply it.
> Unit test TestPureJavaCRC32 warmup code warms up the not-so-important loop in
> PureJavaCRC32.update()
> ----------------------------------------------------------------------------------------------------
>
> Key: HADOOP-7401
> URL: https://issues.apache.org/jira/browse/HADOOP-7401
> Project: Hadoop Common
> Issue Type: Improvement
> Components: test
> Affects Versions: 0.21.0
> Environment: Solaris-Sparcv9; Solaris-AMD64
> Reporter: monica beckwith
> Assignee: monica beckwith
> Priority: Minor
> Fix For: 0.21.0
>
> Attachments: HADOOP-7401.patch
>
> Original Estimate: 1m
> Remaining Estimate: 1m
>
> When the warmup code sequence in TestPureJavaCRC32.java is executed, it sends
> size=len=2 and due to the value of 'trials' in for loop in doBench(), the
> crc.update() gets run > the compile threshold, thus providing the information
> that 'while 0<len<7' is a hot loop and 'while len>7' is a cold loop. This
> brings the MB/s number for len > 7 in PureJavaCRC32.update() way down (e.g.
> ~28.5% for size=len=65536).
> The workaround would be to use size=len=>7 (so just having size=len=2101
> ahead of size=len=2 will do the trick) in the warmup section.
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