Performance Schema Overview

USE performance_schema

SHOW TABLES;
+----------------------------------------------------+
| Tables_in_performance_schema                       |
+----------------------------------------------------+
| accounts                                           |
...
| users                                              |
+----------------------------------------------------+
80 rows in set (0.00 sec)

SHOW VARIABLES LIKE 'performance_schema';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| performance_schema | ON    |
+--------------------+-------+

performance_schema=ON

UPDATE performance_schema.setup_consumers SET ENABLED = 'YES';
UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES';

[mysqld]
performance_schema=ON
performance-schema-instrument='stage/%=ON'
performance-schema-consumer-events-stages-current=ON
performance-schema-consumer-events-stages-history=ON
performance-schema-consumer-events-stages-history-long=ON

SHOW VARIABLES LIKE "perf%";
+--------------------------------------------------------+-------+
| Variable_name                                          | Value |
+--------------------------------------------------------+-------+
| performance_schema                                     | ON    |
...
| performance_schema_users_size                          | 100   |
+--------------------------------------------------------+-------+

SELECT column_name, column_comment FROM information_schema.columns 
  WHERE table_schema='performance_schema' AND table_name='file_instances';
...
*************************** 2. row ***************************
   column_name: EVENT_NAME
column_comment: Instrument name associated with the file.
*************************** 3. row ***************************
   column_name: OPEN_COUNT
column_comment: Open handles on the file. A value of greater than zero means 
                that the file is currently open.
...