PHP-FPM on Apache with split configuration per site – Dimitri.eu http://www.dimitri.eu/php-fpm-apache-split-config-per-site/
vps – PHP-FPM eating memory & Creating many Pools – Ask Ubuntu https://askubuntu.com/questions/393067/php-fpm-eating-memory-creating-many-pools
How to reduce PHP-FPM (php5-fpm) RAM usage by 50% | LinuxBSDos.com http://linuxbsdos.com/2015/02/17/how-to-reduce-php-fpm-php5-fpm-ram-usage-by-about-50/
Using PHP-FPM with Apache on Ubuntu 16.04 https://www.howtoforge.com/tutorial/apache-with-php-fpm-on-ubuntu-16-04/
Apache 2.4 with php5-fpm | DigitalOcean https://www.digitalocean.com/community/questions/apache-2-4-with-php5-fpm