|Server Startup Option||--innodb-additional-mem-pool-size=<value>|
|Possible Values||Integer: Range: 524288 (512K) - 4294967295 (4G)|
|Default Value||1048576 (1M)|
As per MySQL documentation, this pool is used to store data dictionary information and other internal data structures. If InnoDB runs out of memory on this pool, it starts allocating from OS.
Most of the additional memory pool usage goes to tables in the data dictionary and connections. Normally, with increasing number of tables you may need to allocate more memory to this pool. But as modern OS'es have good and fast memory allocating functions, this variable does not hit performance.
Anyhow, if you need to see how much of additional memory pool is being used, it's available via
SHOW ENGINE INNODB STATUS.
additional pool allocatedwill show amount of memory allocated in additional memory pool, the usage. And out of usage,
Dictionary memory allocatedwill show amount of memory being used for data dictionary.
SHOW ENGINE INNODB STATUSshows for
additional pool allocated. It's proportional to (number of tables + number of concurrent connections). Read more: