[DDF] As a Data Grid user, I would like to have a deeper explanation of why I need to spend half of the Heap space in

As a Data Grid user, I would like to have a deeper explanation of why I need to spend half of the Heap space in something else that is not storing cache entries.
For big Openshift pods, like 8GBs, having 4GB just for Heap seems a big waste of resources. It might make sense, but maybe we could elaborate more on why we need these resources.