$ sudo tail /var/log/php7.0-fpm.log
WARNING: [pool www] server reached pm.max_children setting (5), consider raising it
$ sudo vim /etc/php/7.0/fpm/pool.d/www.conf
;pm.max_children = 5
pm.max_children = 10
$ sudo systemctl restart php7.0-fpm.service

$ sudo tail -f /var/log/php7.0-fpm.log
[17-Jan-2017 04:23:08] WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 8 children, there are 0 idle, and 6 total children
$ sudo vim /etc/php/7.0/fpm/pool.d/www.conf
;pm.start_servers = 2
pm.start_servers = 3
;pm.min_spare_servers = 1
pm.min_spare_servers = 2
;pm.max_spare_servers = 3
pm.max_spare_servers = 5
$ sudo systemctl restart php7.0-fpm nginx