1、在MYSQL客户端进行查询：show global status like 'innodb%read%';
2、等待一段时间（5分钟或10分钟）
3、再次在MYSQL客户端进行查询：show global status like 'innodb%read%';
4、使用以下公式计算内存命中率：
两次查询的innodb_buffer_pool_read_requests差
/(两次查询的innodb_buffer_pool_read_requests差
+两次查询的innodb_buffer_pool_read_ahead差
+两次查询的innodb_buffer_pool_reads差)
Innodb_buffer_pool_read_ahead
The number of pages read into the InnoDB buffer pool by the read-ahead background thread.
Innodb_buffer_pool_read_requests
The number of logical read requests.
Innodb_buffer_pool_reads
The number of logical reads that InnoDB could not satisfy from the buffer pool, and had to read directly from disk.