Installing Passenger + Nginx on Ubuntu 18.04 LTS (with APT) on a Linux/Unix production server (part 2) – deployment walkthrough with Ruby, Passenger, Nginx, Ubuntu 18.04 LTS (with APT) and Linux/Unix – Passenger Library

sudo /usr/sbin/passenger-memory-stats

Source: Installing Passenger + Nginx on Ubuntu 18.04 LTS (with APT) on a Linux/Unix production server (part 2) – deployment walkthrough with Ruby, Passenger, Nginx, Ubuntu 18.04 LTS (with APT) and Linux/Unix – Passenger Library