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

[Aaron Ogburn (JIRA)]

Aaron Ogburn created JBCL-185:
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             Summary: 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


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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