Finding Java memory leak when not all used heap is reachable from threads

Question

I am looking into a potential memory leak (or at least memory waste) in a largish Java based system. The JVM is running with a maximum heap size of 5 GB and 2-3GB heap usage is

Answer 1

Since the extra memory is not showing in MAT it's hard to know what to suggest. It isn't true. MAT show unreachable objects. Just go to de Preferences and select check box enabling this options. After MAT restart you will see these objects with details. Of course roots to GC will be not available.