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https://issues.apache.org/jira/browse/HADOOP-15554?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16526616#comment-16526616
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Jonathan Eagles commented on HADOOP-15554:
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[~tlipcon], I was able to verify this doesn't cause a performance regression
for my use cases and environment. The code is correct and I can see how this
can led itself to fix the problem as described above. From a code maintenance
perspective this is better as well. However, I wasn't able to see the 700ms JIT
compilation improvement shown above. Is there an environmental difference(jvm?,
setup?, environment?) that allows for the discrepancy?
I'm happy to put this in as you've shown the work that proves improvement in
your setup. I only wish I could explain why I wasn't able to reproduce this. In
addition, should we broaden the target version. I'm not sure how much 2.9, 3.0,
3.1, 3.2, and trunk have diverged at this point so the backport could be
challenging.
> Improve JIT performance for Configuration parsing
> -------------------------------------------------
>
> Key: HADOOP-15554
> URL: https://issues.apache.org/jira/browse/HADOOP-15554
> Project: Hadoop Common
> Issue Type: Improvement
> Components: conf, performance
> Affects Versions: 3.0.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Minor
> Attachments: hadoop-15554.patch, hadoop-15554.patch
>
>
> In investigating a performance regression for small tasks between Hadoop 2
> and Hadoop 3, we found that the amount of time spent in JIT was significantly
> higher. Using jitwatch we were able to determine that, due to a combination
> of switching from DOM to SAX style parsing and just having more configuration
> key/value pairs, Configuration.loadResource is now getting compiled with the
> C2 compiler and taking quite some time. Breaking that very large function up
> into several smaller ones and eliminating some redundant bits of code
> improves the JIT performance measurably.
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