21.12 Performance Schema System Variables

The Performance Schema implements several system variables that provide configuration information:

mysql> SHOW VARIABLES LIKE 'perf%';
+--------------------------------------------------------+---------+
| Variable_name                                          | Value   |
+--------------------------------------------------------+---------+
| performance_schema                                     | ON      |
| performance_schema_accounts_size                       | 100     |
| performance_schema_digests_size                        | 200     |
| performance_schema_events_stages_history_long_size     | 10000   |
| performance_schema_events_stages_history_size          | 10      |
| performance_schema_events_statements_history_long_size | 10000   |
| performance_schema_events_statements_history_size      | 10      |
| performance_schema_events_waits_history_long_size      | 10000   |
| performance_schema_events_waits_history_size           | 10      |
| performance_schema_hosts_size                          | 100     |
| performance_schema_max_cond_classes                    | 80      |
| performance_schema_max_cond_instances                  | 1000    |
| performance_schema_max_file_classes                    | 50      |
| performance_schema_max_file_handles                    | 32768   |
| performance_schema_max_file_instances                  | 10000   |
| performance_schema_max_mutex_classes                   | 200     |
| performance_schema_max_mutex_instances                 | 1000000 |
| performance_schema_max_rwlock_classes                  | 30      |
| performance_schema_max_rwlock_instances                | 1000000 |
| performance_schema_max_socket_classes                  | 10      |
| performance_schema_max_socket_instances                | 1000    |
| performance_schema_max_stage_classes                   | 150     |
| performance_schema_max_statement_classes               | 165     |
| performance_schema_max_table_handles                   | 10000   |
| performance_schema_max_table_instances                 | 1000    |
| performance_schema_max_thread_classes                  | 50      |
| performance_schema_max_thread_instances                | 1000    |
| performance_schema_session_connect_attrs_size          | 512     |
| performance_schema_setup_actors_size                   | 100     |
| performance_schema_setup_objects_size                  | 100     |
| performance_schema_users_size                          | 100     |
+--------------------------------------------------------+---------+

Performance Schema system variables can be set at server startup on the command line or in option files, and many can be set at runtime. See Section 21.10, “Performance Schema Option and Variable Reference”.

As of MySQL 5.6.6, the Performance Schema automatically sizes the values of several of its parameters at server startup if they are not set explicitly. For more information, see Section 21.2.2, “Performance Schema Startup Configuration”.

Performance Schema system variables have the following meanings: