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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1017) Optimization: Reduce Overhead from ReflectionUtils.newInstance
Date Tue, 13 Feb 2007 22:18:06 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12472895
] 

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

Overall, I like this.  In most cases, where classes are not GC'd, the use of a WeakHashMap
is moot, but it shouldn't hurt and may help in some cases.  But I'd prefer we don't expose
the cache through a public API, nor permit disabling it through a system property.  A larger
public API complicates long-term support.  If the cache size ever becomes an issue then we
can address that then.

> 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: 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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