[jboss-jira] [JBoss JIRA] (JBCL-185) BaseClassLoader.loadClass() is slow under load

[Aaron Ogburn (JIRA)]

     [ https://issues.jboss.org/browse/JBCL-185?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aaron Ogburn updated JBCL-185:
------------------------------

    Attachment: JBCL-185.patch
                BaseClassLoader.java


We have a customer facing this issue currently in a migration effort.  I whipped up a potential fix for them to test that would allow them to cache locally to the BCL to return from BCL.loadClass() calls before trying to go through synchronization and the domain.

They confirmed this change resolved the performance degradation experienced moving from 4.3 to 5.  Attached is the diff file and source file encompassing my changes for this on 2.0.9.GAs BCL.

Would anyone more well versed mind reviewing these changes?  Can we implement these in the JBoss Classloader?

Or would there be a better way to get these loadClass calls to return from cache before synchronizing and bottlenecking?
                
> BaseClassLoader.loadClass() is slow under load
> ----------------------------------------------
>
>                 Key: JBCL-185
>                 URL: https://issues.jboss.org/browse/JBCL-185
>             Project: JBoss ClassLoader
>          Issue Type: Enhancement
>          Components: ClassLoader
>    Affects Versions: JBossCL.2.0.9.GA 
>         Environment: -JBoss Enterprise Application Platform (EAP) 5.1.2
> -JBossCL 2.0.9.GA
>            Reporter: Aaron Ogburn
>            Assignee: Ales Justin
>         Attachments: BaseClassLoader.java, JBCL-185.patch
>
>
> Classloader performance dropped from EAP 4.3 to 5.  Thread dumps show threads facing contention in the classloader:
>    java.lang.Thread.State: BLOCKED (on object monitor)
> 	at org.jboss.classloader.spi.base.BaseClassLoader.doLoadClass(BaseClassLoader.java:495)
> 	- waiting to lock <0x80e22960> (a org.jboss.classloader.spi.base.BaseClassLoader)
> 	at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:447)
> 	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
> 	at org.jboss.classloading.spi.DelegatingClassLoader.loadClass(DelegatingClassLoader.java:87)
> 	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
> 	at org.jboss.util.loading.DelegatingClassLoader.loadClass(DelegatingClassLoader.java:97)
> 	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
> These are repeat lookups.  The thread and classloader trace logging show that these look ups are not returning cached values from checkCacheAndBlackList() and so they are having to go progress through doLoadClass() and the baseclassloderdomain to finally return the class from another classloaders cache.  This is bad as threads are forced to synchronize to return a cached class from elsewhere whereas the cached value return could all happen concurrently.

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