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https://issues.apache.org/jira/browse/HADOOP-1017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12473793
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Owen O'Malley commented on HADOOP-1017:
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I'd vote for the synchronized map. The failure mode would just be that you look
up the constructor a second time.
> Optimization: Reduce Overhead from ReflectionUtils.newInstance
> --------------------------------------------------------------
>
> Key: HADOOP-1017
> URL: https://issues.apache.org/jira/browse/HADOOP-1017
> Project: Hadoop
> Issue Type: Improvement
> Components: util
> Reporter: Ron Bodkin
> Attachments: cacheCtor.patch, ReflectionUtils.patch.txt,
> TestReflectionUtils.java
>
>
> I found that a significant amount of time on my project was being spent in
> creating constructors for each row of data. I dramatically optimized this
> performance by creating a simple WeakHashMap to cache constructors by class.
> For example, in a sample job I find that ReflectionUtils.newInstance takes
> 200 ms (2% of total) with the cache enabled, but it uses 900 ms (6% of total)
> without the cache.
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