We have a Java webapp that we upgraded from Java 1.5.0.19 to Java 1.6.0.21 

/usr/java/jdk1.6.0_21/bin/java -server -Xms2000m -Xmx3000m -XX:MaxPermSize=256m -Djava.awt.headless=true -Dwg.environment=production -Djava.io.tmpdir=/var/cache/jetty -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=31377 -Dcom.sun.management.jmxremote.authenticate=true -Dcom.sun.management.jmxremote.ssl=false -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/tmp/webapp -Dprogram.name=run.sh -Djava.endorsed.dirs=/opt/3p/jboss/lib/endorsed -classpath /opt/3p/jboss/bin/run.jar:/usr/java/jdk1.6.0_21/lib/tools.jar org.jboss.Main -c default

As you can see it should preallocate 2GB of heap and max out at 3GB (why we preallocate so much is because this app is ancient and poorly designed so has a ton of things to load up). The issue we have seen recently after upgrading to the 1.6 is that on occasion memory goes through the roof. While memory usage is likely an app issue the JVM is exceeding the 3GB max setup for heap. Using top I see:

 PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND    
8449 apache    18   0 19.6g 6.9g 5648 S  4.0 84.8  80:42.27 java

So how could a JVM with 3GB heap, 256MB permgen, and even some overhead consume 6.9GB? Bug in the JVM that would be fixed by upgrading to build #35? Something missing on what in java could be using the extra memory? Just trying to see if anyone has seen this before.

java memory-management memory-leaks
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