vps 只有1g，mysql8占用200多，原因是mysql8 默认开启了performance_schema 内存监控程序。

1.查询内存占用（前提是开启了performance_schema )

 SELECT SUBSTRING_INDEX(event_name,'/',2) AS
       code_area, FORMAT_BYTES(SUM(current_alloc))
       AS current_alloc
       FROM sys.x$memory_global_by_current_bytes
       GROUP BY SUBSTRING_INDEX(event_name,'/',2)
       ORDER BY SUM(current_alloc) DESC;

返回如下：

+---------------------------+---------------+

| code_area                 | current_alloc |

+---------------------------+---------------+

| memory/performance_schema | 116.20 MiB    |

| memory/innodb             | 72.89 MiB     |

| memory/mysys              | 8.54 MiB      |

| memory/sql                | 7.77 MiB      |

| memory/temptable          | 1.00 MiB      |

| memory/mysqld_openssl     | 134.68 KiB    |

| memory/mysqlx             | 2.62 KiB      |

| memory/myisam             |  696 bytes    |

| memory/csv                |   88 bytes    |

| memory/blackhole          |   88 bytes    |

| memory/vio                |   16 bytes    |

+---------------------------+---------------+

2.宝塔—-已安装软件—-mysql—-配置my.cnf

[mysqld]
performance_schema = OFF

3.注意关掉这个监控程序，第1步的操作会返回空。