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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1017) Optimization: Reduce Overhead from ReflectionUtils.newInstance
Date Fri, 16 Feb 2007 19:46:05 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12473804
] 

Doug Cutting commented on HADOOP-1017:
--------------------------------------

Hadoop requires Java5 already, so, yes, let's use ConcurrentMap for thread-safety and not
worry about GCing classes.

> 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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