NodeJs - RSS and external memory increases significantly, heap memory increases slowly. What can be the causes?

In my NodeJS application:

1.Is it correct that RSS and external memory increases significantly, but heap memory increases slowly?

2. Is it correct that the external memory increases more than the heapTotal?

I tried using the chrome inspect, but as soon as i launch the snapshots the application crashes. Also, i don't think analyzing the heap memory i find the problem.

see the graph here

Any suggestions?