1.
查看一个page_size 的大小
mysql> show variables like '%page_s%';
+------------------+-------+
| Variable_name | Value |
+------------------+-------+
| innodb_page_size | 16384 |
| large_page_size | 0 |
+------------------+-------+
2 rows in set (0.00 sec)
show engine innodb status\G
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 8795455488
Dictionary memory allocated 7314135
Buffer pool size 524224
Free buffers 32775
Database pages 476701
Old database pages 175315
Modified db pages 89529
memory allocated 内存 单位bytes
Buffer pool size buffer的页数 ，一个页的默认大小是16K
524224*16/1024.00=8191MB
2.
SELECT @@innodb_buffer_pool_size/1024/1024/1024;
参考：
MySQL :: MySQL 8.0 Reference Manual :: 7.1.10 Server Status Variables
MySQL :: MySQL 8.0 Reference Manual :: 17.8.3.1 Configuring InnoDB Buffer Pool Size
