JVM exceeds maximum memory defined with -Xmx

Question

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 -Djav         


        

Answer 1

So how could a JVM with 3GB heap, 256MB permgen, and even some overhead consume 6.9GB?

Possible explanations include:

• lots and lots of thread stacks,
• memory-mapped files that are not being closed when they should be,
• some native code library using (possibly leaking) out-of-heap memory.

I would be inclined to blame the application before blaming the JVM.