We are running an application on jboss-eap-6.0.1 with java version shown below
$ java -version
java version "1.6.0_45"
Java(TM) SE Runtime Environment (build 1.6.0_45-b06)
Java HotSpot(TM) 64-Bit Server VM (build 20.45-b01, mixed mode)
When the heap starts getting full, I start seeing a large number of "Unloading class..." messages like the ones below in the stdout logs. We do not have the -XX:+CMSClassUnloadingEnabled flag set and from what I've found, we should not be unloading classes. I did find a posting on Atlassian's site (https://confluence.atlassian.com/display/JIRAKB/%5BUnloading+class+sun.reflect.GeneratedMethodAccessor%5D+found+in+Tomcat+logs) that indicates that the JVM will unload classes without the -XX:+CMSClassUnloadingEnabled flag set if "the JVM finds it physically does not have the resources that have been allocated to it, (usually due to either VM ballooning or resource stealing)". I have not seen discussions of this elsewhere and wanted to understand if it's possible that the JVM might try to collect classes as a last ditch effort to gain memory or if there might be some other explanation such as the options specified on our command line implicitly sets the -XX:+CMSClassUnloadingEnabled flag. Any insights are appreciated.
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor897]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor709]
[Unloading class sun.reflect.GeneratedConstructorAccessor570]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor996]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor816]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor362]
[Unloading class sun.reflect.GeneratedMethodAccessor257]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor46]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor775]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor210]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor332]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor168]
[Unloading class sun.reflect.GeneratedSerializationConstructorAccessor149]
The command line options are
java
-D[Standalone]
-server
-XX:+UseCompressedOops
-XX:+DisableExplicitGC
-Dsun.rmi.dgc.client.gcInterval=36000000
-Dsun.rmi.dgc.server.gcInterval=36000000
-Djs.license.directory=/opt/app/AgentDesktop/resources/jasper
-Djava.io.tmpdir=/opt/tmp
-Xloggc:/opt/app/logs/PRD00_C_gc.log
-XX:+PrintGCTimeStamps
-XX:+PrintGCDetails
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=/opt/app/logs/heapDump/PRD00_C
-Dorg.apache.commons.logging.Log=org.apache.commons.logging.impl.SimpleLog
-Dorg.apache.commons.logging.simplelog.log.org.apache.commons.httpclient.wire=ERROR
-XX:+UseConcMarkSweepGC
-XX:+CMSIncrementalMode
-Xmx2560m
-Xms2560m
-XX:NewSize=512M
-XX:MaxPermSize=512m
-XX:PermSize=256M
-XX:+UseCompressedOops
-XX:AutoBoxCacheMax=2048
-Dorg.jboss.boot.log.file=/opt/app/logs/jboss/PRD00_C/boot.log
-Dlogging.configuration=file:/opt/app/jboss-eap-6.0.1/server/PRD00_C/configuration/logging.properties
-jar
/opt/app/jboss/jboss-modules.jar
-mp
/opt/app/jboss/modules
-jaxpmodule
javax.xml.jaxp-provider
org.jboss.as.standalone
-Djboss.home.dir=/opt/app/jboss
-Djboss.server.base.dir=/opt/app/jboss-eap-6.0.1/server/PRD00_C
--server-config=standalone-full-PRD.xml
--properties=file:/opt/app/AgentDesktop/work/jboss/combined.101932939.properties
-Djboss.socket.binding.port-offset=300
-Djboss.server.base.dir=/opt/app/jboss/server/PRD00_C
-Djboss.server.log.dir=/opt/app/logs/jboss/PRD00_C
-Dcom.kana.properties.url=file:/opt/app/AgentDesktop/work/jboss/combined.101932939.properties
-Dcom.gtnet.systemProperties.override.url=file:/opt/app/AgentDesktop/config/PRD//override.properties
-Dcore.home=/opt/app/AgentDesktop
-Denvironment.dir=/opt/app/AgentDesktop/config/PRD
-Denvironment.url=file:/opt/app/AgentDesktop/config/PRD/
-Drelease.id=1
-Dorg.apache.tomcat.util.http.Parameters.MAX_COUNT=1000
-Dorg.jboss.as.logging.per-deployment=false
-b
0.0.0.0
