To be honest this isn't available currently. The only way I can think of getting an estimate would be to take a heap dump and use a tool such as Eclipse MAT . You can go ahead and log an improvement though to expose our internal counter if you want. Unfortunately it lives in Caffeine  and we would need to extract it and expose it. We do however currently expose how much off heap memory is in use if you are using Infinispan 9 with OFF HEAP memory container .