I think, we have some work to document what those values mean. RES in graph - is not total RSS memory usage, it is memory ruby has allocated on C heap via `mall

I think, we have some work to document what those values mean. RES in graph - is not total RSS memory usage, it is memory ruby has allocated on C heap via `malloc` calls. If you are familiar with Ruby internals, ruby heap can store small sized objects (such as smaller strings, smaller arrays etc) in its own heap, but for larger objects ruby uses `malloc` and the ruby heap itself just keeps a pointer to memory allocated. The RES size in graph is approximately that value. Total RSS size of ruby process is lot bigger, it is combination of C heap, Ruby heap and other allocations which ruby is not even aware of (such as a C extension using `malloc` calls).