Large grain of dict_sys lock by table creation affects performance

Our test guys tried to create tables with 500 concurrent sessions (each session 200 tables)and cause slow queries.
I used pstack to inspect the stacks and found most threads are waiting for the mutex of global variable dict_sys

I viewed the related codes in method
ha_innobase::create
and think the lock range is too large.

row_mysql_lock_data_dictionary / row_mysql_unlock_data_dictionary between
error = info.create_table(own_trx)

In create_table_info_t::create_table, there are a lot of object allocation or simply setting members in those objects before attaching them to the cache of global variable dict_sys. IMO those steps don't require mutex of global dict.

Would it be better if we make the mutex dict_sys fine-grained instead of locking whole process of create_table_info_t::create_table