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This section briefly introduces the Performance Schema with examples that show how to use it. For additional examples, seeSection 29.19, “Using the Performance Schema to Diagnose Problems”.

The Performance Schema is enabled by default. To enable or disable it explicitly, start the server with theperformance_schema variable set to an appropriate value. For example, use these lines in the servermy.cnf file:

[mysqld]performance_schema=ON

When the server starts, it seesperformance_schema and attempts to initialize the Performance Schema. To verify successful initialization, use this statement:

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

A value ofON means that the Performance Schema initialized successfully and is ready for use. A value ofOFF means that some error occurred. Check the server error log for information about what went wrong.

The Performance Schema is implemented as a storage engine, so you can see it listed in the output from the Information SchemaENGINES table or theSHOW ENGINES statement:

mysql> SELECT * FROM INFORMATION_SCHEMA.ENGINES       WHERE ENGINE='PERFORMANCE_SCHEMA'\G*************************** 1. row ***************************      ENGINE: PERFORMANCE_SCHEMA     SUPPORT: YES     COMMENT: Performance SchemaTRANSACTIONS: NO          XA: NO  SAVEPOINTS: NOmysql> SHOW ENGINES\G...      Engine: PERFORMANCE_SCHEMA     Support: YES     Comment: Performance SchemaTransactions: NO          XA: NO  Savepoints: NO...

ThePERFORMANCE_SCHEMA storage engine operates on tables in theperformance_schema database. You can makeperformance_schema the default database so that references to its tables need not be qualified with the database name:

mysql> USE performance_schema;

Performance Schema tables are stored in theperformance_schema database. Information about the structure of this database and its tables can be obtained, as for any other database, by selecting from theINFORMATION_SCHEMA database or by usingSHOW statements. For example, use either of these statements to see what Performance Schema tables exist:

mysql> SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES       WHERE TABLE_SCHEMA = 'performance_schema';+------------------------------------------------------+| TABLE_NAME                                           |+------------------------------------------------------+| accounts                                             || cond_instances                                       |...| events_stages_current                                || events_stages_history                                || events_stages_history_long                           || events_stages_summary_by_account_by_event_name       || events_stages_summary_by_host_by_event_name          || events_stages_summary_by_thread_by_event_name        || events_stages_summary_by_user_by_event_name          || events_stages_summary_global_by_event_name           || events_statements_current                            || events_statements_history                            || events_statements_history_long                       |...| file_instances                                       || file_summary_by_event_name                           || file_summary_by_instance                             || host_cache                                           || hosts                                                || memory_summary_by_account_by_event_name              || memory_summary_by_host_by_event_name                 || memory_summary_by_thread_by_event_name               || memory_summary_by_user_by_event_name                 || memory_summary_global_by_event_name                  || metadata_locks                                       || mutex_instances                                      || objects_summary_global_by_type                       || performance_timers                                   || replication_connection_configuration                 || replication_connection_status                        || replication_applier_configuration                    || replication_applier_status                           || replication_applier_status_by_coordinator            || replication_applier_status_by_worker                 || rwlock_instances                                     || session_account_connect_attrs                        || session_connect_attrs                                || setup_actors                                         || setup_consumers                                      || setup_instruments                                    || setup_objects                                        || socket_instances                                     || socket_summary_by_event_name                         || socket_summary_by_instance                           || table_handles                                        || table_io_waits_summary_by_index_usage                || table_io_waits_summary_by_table                      || table_lock_waits_summary_by_table                    || threads                                              || users                                                |+------------------------------------------------------+mysql> SHOW TABLES FROM performance_schema;+------------------------------------------------------+| Tables_in_performance_schema                         |+------------------------------------------------------+| accounts                                             || cond_instances                                       || events_stages_current                                || events_stages_history                                || events_stages_history_long                           |...

The number of Performance Schema tables increases over time as implementation of additional instrumentation proceeds.

The name of theperformance_schema database is lowercase, as are the names of tables within it. Queries should specify the names in lowercase.

To see the structure of individual tables, useSHOW CREATE TABLE:

mysql> SHOW CREATE TABLE performance_schema.setup_consumers\G*************************** 1. row ***************************       Table: setup_consumersCreate Table: CREATE TABLE `setup_consumers` (  `NAME` varchar(64) NOT NULL,  `ENABLED` enum('YES','NO') NOT NULL,  PRIMARY KEY (`NAME`)) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

Table structure is also available by selecting from tables such asINFORMATION_SCHEMA.COLUMNS or by using statements such asSHOW COLUMNS.

Tables in theperformance_schema database can be grouped according to the type of information in them: Current events, event histories and summaries, object instances, and setup (configuration) information. The following examples illustrate a few uses for these tables. For detailed information about the tables in each group, seeSection 29.12, “Performance Schema Table Descriptions”.

Initially, not all instruments and consumers are enabled, so the performance schema does not collect all events. To turn all of these on and enable event timing, execute two statements (the row counts may differ depending on MySQL version):

mysql> UPDATE performance_schema.setup_instruments       SET ENABLED = 'YES', TIMED = 'YES';Query OK, 560 rows affected (0.04 sec)mysql> UPDATE performance_schema.setup_consumers       SET ENABLED = 'YES';Query OK, 10 rows affected (0.00 sec)

To see what the server is doing at the moment, examine theevents_waits_current table. It contains one row per thread showing each thread's most recent monitored event:

mysql> SELECT *       FROM performance_schema.events_waits_current\G*************************** 1. row ***************************            THREAD_ID: 0             EVENT_ID: 5523         END_EVENT_ID: 5523           EVENT_NAME: wait/synch/mutex/mysys/THR_LOCK::mutex               SOURCE: thr_lock.c:525          TIMER_START: 201660494489586            TIMER_END: 201660494576112           TIMER_WAIT: 86526                SPINS: NULL        OBJECT_SCHEMA: NULL          OBJECT_NAME: NULL           INDEX_NAME: NULL          OBJECT_TYPE: NULLOBJECT_INSTANCE_BEGIN: 142270668     NESTING_EVENT_ID: NULL   NESTING_EVENT_TYPE: NULL            OPERATION: lock      NUMBER_OF_BYTES: NULL                FLAGS: 0...

This event indicates that thread 0 was waiting for 86,526 picoseconds to acquire a lock onTHR_LOCK::mutex, a mutex in themysys subsystem. The first few columns provide the following information:

The history tables contain the same kind of rows as the current-events table but have more rows and show what the server has been doing“recently” rather than“currently.” Theevents_waits_history andevents_waits_history_long tables contain the most recent 10 events per thread and most recent 10,000 events, respectively. For example, to see information for recent events produced by thread 13, do this:

mysql> SELECT EVENT_ID, EVENT_NAME, TIMER_WAIT       FROM performance_schema.events_waits_history       WHERE THREAD_ID = 13       ORDER BY EVENT_ID;+----------+-----------------------------------------+------------+| EVENT_ID | EVENT_NAME                              | TIMER_WAIT |+----------+-----------------------------------------+------------+|       86 | wait/synch/mutex/mysys/THR_LOCK::mutex  |     686322 ||       87 | wait/synch/mutex/mysys/THR_LOCK_malloc  |     320535 ||       88 | wait/synch/mutex/mysys/THR_LOCK_malloc  |     339390 ||       89 | wait/synch/mutex/mysys/THR_LOCK_malloc  |     377100 ||       90 | wait/synch/mutex/sql/LOCK_plugin        |     614673 ||       91 | wait/synch/mutex/sql/LOCK_open          |     659925 ||       92 | wait/synch/mutex/sql/THD::LOCK_thd_data |     494001 ||       93 | wait/synch/mutex/mysys/THR_LOCK_malloc  |     222489 ||       94 | wait/synch/mutex/mysys/THR_LOCK_malloc  |     214947 ||       95 | wait/synch/mutex/mysys/LOCK_alarm       |     312993 |+----------+-----------------------------------------+------------+

As new events are added to a history table, older events are discarded if the table is full.

Summary tables provide aggregated information for all events over time. The tables in this group summarize event data in different ways. To see which instruments have been executed the most times or have taken the most wait time, sort theevents_waits_summary_global_by_event_name table on theCOUNT_STAR orSUM_TIMER_WAIT column, which correspond to aCOUNT(*) orSUM(TIMER_WAIT) value, respectively, calculated over all events:

mysql> SELECT EVENT_NAME, COUNT_STAR       FROM performance_schema.events_waits_summary_global_by_event_name       ORDER BY COUNT_STAR DESC LIMIT 10;+---------------------------------------------------+------------+| EVENT_NAME                                        | COUNT_STAR |+---------------------------------------------------+------------+| wait/synch/mutex/mysys/THR_LOCK_malloc            |       6419 || wait/io/file/sql/FRM                              |        452 || wait/synch/mutex/sql/LOCK_plugin                  |        337 || wait/synch/mutex/mysys/THR_LOCK_open              |        187 || wait/synch/mutex/mysys/LOCK_alarm                 |        147 || wait/synch/mutex/sql/THD::LOCK_thd_data           |        115 || wait/io/file/myisam/kfile                         |        102 || wait/synch/mutex/sql/LOCK_global_system_variables |         89 || wait/synch/mutex/mysys/THR_LOCK::mutex            |         89 || wait/synch/mutex/sql/LOCK_open                    |         88 |+---------------------------------------------------+------------+mysql> SELECT EVENT_NAME, SUM_TIMER_WAIT       FROM performance_schema.events_waits_summary_global_by_event_name       ORDER BY SUM_TIMER_WAIT DESC LIMIT 10;+----------------------------------------+----------------+| EVENT_NAME                             | SUM_TIMER_WAIT |+----------------------------------------+----------------+| wait/io/file/sql/MYSQL_LOG             |     1599816582 || wait/synch/mutex/mysys/THR_LOCK_malloc |     1530083250 || wait/io/file/sql/binlog_index          |     1385291934 || wait/io/file/sql/FRM                   |     1292823243 || wait/io/file/myisam/kfile              |      411193611 || wait/io/file/myisam/dfile              |      322401645 || wait/synch/mutex/mysys/LOCK_alarm      |      145126935 || wait/io/file/sql/casetest              |      104324715 || wait/synch/mutex/sql/LOCK_plugin       |       86027823 || wait/io/file/sql/pid                   |       72591750 |+----------------------------------------+----------------+

These results show that theTHR_LOCK_malloc mutex is“hot,” both in terms of how often it is used and amount of time that threads wait attempting to acquire it.

Instance tables document what types of objects are instrumented. An instrumented object, when used by the server, produces an event. These tables provide event names and explanatory notes or status information. For example, thefile_instances table lists instances of instruments for file I/O operations and their associated files:

mysql> SELECT *       FROM performance_schema.file_instances\G*************************** 1. row *************************** FILE_NAME: /opt/mysql-log/60500/binlog.000007EVENT_NAME: wait/io/file/sql/binlogOPEN_COUNT: 0*************************** 2. row *************************** FILE_NAME: /opt/mysql/60500/data/mysql/tables_priv.MYIEVENT_NAME: wait/io/file/myisam/kfileOPEN_COUNT: 1*************************** 3. row *************************** FILE_NAME: /opt/mysql/60500/data/mysql/columns_priv.MYIEVENT_NAME: wait/io/file/myisam/kfileOPEN_COUNT: 1...

Setup tables are used to configure and display monitoring characteristics. For example,setup_instruments lists the set of instruments for which events can be collected and shows which of them are enabled:

mysql> SELECT NAME, ENABLED, TIMED       FROM performance_schema.setup_instruments;+---------------------------------------------------+---------+-------+| NAME                                              | ENABLED | TIMED |+---------------------------------------------------+---------+-------+...| stage/sql/end                                     | NO      | NO    || stage/sql/executing                               | NO      | NO    || stage/sql/init                                    | NO      | NO    || stage/sql/insert                                  | NO      | NO    |...| statement/sql/load                                | YES     | YES   || statement/sql/grant                               | YES     | YES   || statement/sql/check                               | YES     | YES   || statement/sql/flush                               | YES     | YES   |...| wait/synch/mutex/sql/LOCK_global_read_lock        | YES     | YES   || wait/synch/mutex/sql/LOCK_global_system_variables | YES     | YES   || wait/synch/mutex/sql/LOCK_lock_db                 | YES     | YES   || wait/synch/mutex/sql/LOCK_manager                 | YES     | YES   |...| wait/synch/rwlock/sql/LOCK_grant                  | YES     | YES   || wait/synch/rwlock/sql/LOGGER::LOCK_logger         | YES     | YES   || wait/synch/rwlock/sql/LOCK_sys_init_connect       | YES     | YES   || wait/synch/rwlock/sql/LOCK_sys_init_slave         | YES     | YES   |...| wait/io/file/sql/binlog                           | YES     | YES   || wait/io/file/sql/binlog_index                     | YES     | YES   || wait/io/file/sql/casetest                         | YES     | YES   || wait/io/file/sql/dbopt                            | YES     | YES   |...

To understand how to interpret instrument names, seeSection 29.6, “Performance Schema Instrument Naming Conventions”.

To control whether events are collected for an instrument, set itsENABLED value toYES orNO. For example:

mysql> UPDATE performance_schema.setup_instruments       SET ENABLED = 'NO'       WHERE NAME = 'wait/synch/mutex/sql/LOCK_mysql_create_db';

The Performance Schema uses collected events to update tables in theperformance_schema database, which act as“consumers” of event information. Thesetup_consumers table lists the available consumers and which are enabled:

mysql> SELECT * FROM performance_schema.setup_consumers;+----------------------------------+---------+| NAME                             | ENABLED |+----------------------------------+---------+| events_stages_current            | NO      || events_stages_history            | NO      || events_stages_history_long       | NO      || events_statements_cpu            | NO      || events_statements_current        | YES     || events_statements_history        | YES     || events_statements_history_long   | NO      || events_transactions_current      | YES     || events_transactions_history      | YES     || events_transactions_history_long | NO      || events_waits_current             | NO      || events_waits_history             | NO      || events_waits_history_long        | NO      || global_instrumentation           | YES     || thread_instrumentation           | YES     || statements_digest                | YES     |+----------------------------------+---------+

To control whether the Performance Schema maintains a consumer as a destination for event information, set itsENABLED value.

For more information about the setup tables and how to use them to control event collection, seeSection 29.4.2, “Performance Schema Event Filtering”.

There are some miscellaneous tables that do not fall into any of the previous groups. For example,performance_timers lists the available event timers and their characteristics. For information about timers, seeSection 29.4.1, “Performance Schema Event Timing”.