The above is suspect #2.
Suspect #3 is this:
6.044 instances of "org.jboss.tools.common.model.filesystems.impl.JarSystemImpl", loaded by "org.jboss.tools.common.model" occupy 37.818.184 (10,02%) bytes.
Both hang off the same org.eclipse.jdt.core.IElementChangedListener[]
So that's 28% of used memory :|