I installed Nginx on different servers. They have almost the same php and nginx settings; but memory usage for each php-fpm is significantly different. When checking by top in ssh, VIRT varies from 20k to 60k; RES from 5k to 20k; SHR from 3k to 15k.

We can simply adjust the number php-fpm processes in config, but how we can control the memory usage by each php-fpm process?