the memory distribution of nodejs

When I start a new nodejs and type process.memoryUsage(), it shows

> process.memoryUsage() { rss: 11296768, heapTotal: 7195904, heapUsed: 2964776 }

so the nodejs uses the 11M memory and v8's heap uses 7M of them.

What else consumes the remaining 11-7=4M memory, the c++ part of nodejs? libuv? v8 itself?

Is there any methods or tools to see the memory distribution?

ps: I don't need node-heap/node-memwatch to detect the memory in v8 heap. They are mainly measuring the memory used by js project (js files). I want to know the memory used by node itself. Which parts use the remaining 4M, and how much does each part use.