$ top   ←メモリ使用量
 mysql
 php-fpm ← 複数ある

mysql> show variables like 'table_definition_cache';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| table_definition_cache | 1400  |
+------------------------+-------+

mysql> show variables like 'performance_schema';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| performance_schema | ON    |
+--------------------+-------+

# vi /etc/my.cnf

[mysql.d]
# 以下を追記
table_definition_cache = 400
performance_schema = 0

#vi /etc/php-fpm.d/www.cnf

pm = static
pm.max_children = 2
pm.max_requests = 500

# service php-fpm restart

https://autovice.jp/articles/104