• performance_schema_max_table_instances

The maximum number of instrumented table objects

• table_definition_cache

The number of table definitions (from .frm files) that can be stored in the definition cache. If you use a large number of tables, you can create a large table definition cache to speed up opening of tables. The table definition cache takes less space and does not use file descriptors, unlike the normal table cache. The minimum and default values are both 400.

• table_open_cache
The number of open tables for all threads. Increasing this value increases the number of file descriptors that mysqld requires.

table_open_cache 指的是缓存数据文件的描述符(Linux/Unix)相关信息

References:

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