Mysql server memory variables

join_buffer_size: (PER SESSION) Controls the amount of memory allocated to perform joins on tables that have no keys which can be used to perform a condition filter. Allocated for each table joined without necessary filter conditions.

key_buffer_size: (GLOBAL) (MyISAM-only) Controls the amount of memory allocated to the MyISAM index key cache.

innodb_buffer_pool_size: (GLOBAL) (InnoDB-only) Controls the amount of memory allocated to the InnoDB cache containing both clustered data and secondary index pages.

innodb_additional_mem_pool_size: (GLOBAL) (InnoDB-only) Controls the amount of memory allocated to the buffer storing the InnoDB internal data dictionary.

innodb_log_buffer_size: (GLOBAL) (InnoDB-only) Controls the amount of memory allocated to the buffer storing InnoDB write-ahead log entries.

query_cache_size: (GLOBAL) Controls the amount of memory allocated to the Query Cache.

read_buffer_size: (PER SESSION) Controls the amount of memory allocated to the connecting thread in order to process a table scan.

read_rnd_buffer_size: (PER SESSION) Controls the amount of memory allocated to the buffer used to read previously sorted results.

sort_buffer_size: (PER SESSION) Controls the amount memory allocated to the buffer used to sort result sets before returning the set to the calling client.

thread_stack: (PER SESSION) Controls the default stack memory allocated for each connecting thread.

tmp_table_size: (GLOBAL) Controls the maximum memory to allocate to a temporary table before MySQL converts it into an on-disk MyISAM table.

thread_cache_size: (GLOBAL) Determines the number of thread connection objects that MySQL keeps in a cache to mitigate resource creation costs.