Comment 5 for bug 1441908

table_definition_cache is one of the many sizing hints used by PFS.

=======
        /* Add sizing hints from the server sizing parameters. */
        pfs_param.m_hints.m_table_definition_cache= table_def_size;
        pfs_param.m_hints.m_table_open_cache= table_cache_size;
        pfs_param.m_hints.m_max_connections= max_connections;
 pfs_param.m_hints.m_open_files_limit= requested_open_files;
===========

With a large value for any of these, the server chooses a profile for PFS among small, medium or large:

https://github.com/mysql/mysql-server/blob/5.6/storage/perfschema/pfs_autosize.cc#L121
https://github.com/mysql/mysql-server/blob/5.6/storage/perfschema/pfs_autosize.cc#L175