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From "haruhiko nishi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OGNL-228) Is ognl.OgnlRuntime some root cause of PermGen OutOfMemoryError problem?
Date Thu, 13 Dec 2012 14:48:12 GMT

    [ https://issues.apache.org/jira/browse/OGNL-228?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13531045#comment-13531045
] 

haruhiko nishi commented on OGNL-228:
-------------------------------------

There are indeed other DelegatingClassLoaders also observed in the heap dump, as other frame
works also uses reflective method calls. 
However, there is difference. I see no "other classloader" between the Thread(GC root) and
the DelegatingClassLoader. For instance, DelegatingClassLoaders which is created upon reflective
call made by an object returned by DefaultListableBeanFactory of springframework has the GC
root of a Thread which probably terminates only when JBoss is shutdown. 
In the ognl.OgnlRuntime case, if its GC root, which probably is a request Thread, would have
called a method reflectively in more "direct" manner, the DelegatingClassLoader holding sun.reflect.GeneratedMethodAccessorXXX
could be expelled eventually. However, as this is done though ognl.OgnlRuntime loaded by org.jboss.classloader.spi.base.BaseClassLoader,
which has a different GC root, the sun.reflect.GeneratedMethodAccessorXXX remains, because
the ognl.OgnlRuntime holds them in its HashMap. 
My analyzation may be wrong, but the old post at http://grokbase.com/t/struts/user/0948kcdd77/struts-and-permgen-errors-with-ognl-method-param
says, "new ones keep coming in almost on every request (as far as I can tell, refreshing a
page almost always triggers new ones)." 
                
> Is ognl.OgnlRuntime some root cause of PermGen OutOfMemoryError problem?
> ------------------------------------------------------------------------
>
>                 Key: OGNL-228
>                 URL: https://issues.apache.org/jira/browse/OGNL-228
>             Project: Commons OGNL
>          Issue Type: Bug
>         Environment: RHEL 6 x64
>            Reporter: haruhiko nishi
>            Priority: Critical
>              Labels: OutOfMemoryError
>
> While analyzing several heap dumps using Yourkit, we have observed many instances of
DelegatingClassLoader, or more precisely sun.reflect.GeneratedMethodAccessorXXX, where XXX
represents some sequential numbers, were created through the usage of Java reflection by the
frameworks implemented in our web application.
> GeneratedMethodAccessorXXX is allegedly used for some sort of reflection optimization
mechanism according to the url at http://www-01.ibm.com/support/docview.wss?uid=swg21566549.
> Because this is what seems to be eating up our memory allocated for PermGen, as the number
of the DelegatingClassLoader is gradually increased and JVM crushes with OutOfMemoryError,
we scrutinized what is possibly blocking these DelegatingClassLoaders from being garbage collected
and found many of them are relevant to _methodParameterTypesCache of ognl.OgnlRuntime.
> Is there any known problems regarding this issue?

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