/etc/php/7.0/fpm/pool.d/www.conf:

pm = dynamic
pm.max_children = 30 (original: 5)
pm.start_servers = 3 (original: 1)
pm.min_spare_servers = 2 (original: 1)
pm.max_spare_servers = 4 (original: 3)
pm.max_requests = 500 (originally commented)