Server tuning is a black art, and I don't have much experience with nginx servers. So I'm really not prepared to offer advice on your settings, except to comment that yes, it certainly looks to me that pm.max_children should be higher than 5. I see the tech staff have set it to 50 on our departmental server (8 core, 16 GB) but I'm not sure whether that's a well-calculated load-tested number or just a hack by someone.
I am however curious as to why you're using nginx? Moodle servers usually run Apache and after our own departmental experiences setting up a Moodle server on nginx, I'm wondering why people don't just stick with Apache!
I am however curious as to why you're using nginx? Moodle servers usually run Apache and after our own departmental experiences setting up a Moodle server on nginx, I'm wondering why people don't just stick with Apache!