22.10 Performance Schema System Variables

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

mysql> SHOW VARIABLES LIKE 'perf%';
+---------------------------------------------------+---------+
| Variable_name                                     | Value   |
+---------------------------------------------------+---------+
| performance_schema                                | ON      |
| performance_schema_events_waits_history_long_size | 10000   |
| performance_schema_events_waits_history_size      | 10      |
| 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_table_handles              | 100000  |
| performance_schema_max_table_instances            | 50000   |
| performance_schema_max_thread_classes             | 50      |
| performance_schema_max_thread_instances           | 1000    |
+---------------------------------------------------+---------+

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 22.9, “Performance Schema Option and Variable Reference”.

Performance Schema system variables have the following meanings:

performance_schema
Introduced 5.5.3
Command-Line Format --performance_schema=#
System Variable Name performance_schema
Variable Scope Global
Dynamic Variable No
Permitted Values Type boolean
Default OFF
The value of this variable is ON or OFF to indicate whether the Performance Schema is enabled. By default, the value is OFF. At server startup, you can specify this variable with no value or a value of 1 to enable it, or with a value of 0 to disable it.

performance_schema_events_waits_history_long_size

Introduced	5.5.3
Command-Line Format	`--performance_schema_events_waits_history_long_size=#`
System Variable	Name	`performance_schema_events_waits_history_long_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`10000`

The number of rows in the events_waits_history_long table.

performance_schema_events_waits_history_size

Introduced	5.5.3
Command-Line Format	`--performance_schema_events_waits_history_size=#`
System Variable	Name	`performance_schema_events_waits_history_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`10`

The number of rows per thread in the events_waits_history table.

performance_schema_max_cond_classes

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_cond_classes=#`
System Variable	Name	`performance_schema_max_cond_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`80`

The maximum number of condition instruments.

performance_schema_max_cond_instances

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_cond_instances=#`
System Variable	Name	`performance_schema_max_cond_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`1000`

The maximum number of instrumented condition objects.

performance_schema_max_file_classes

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_file_classes=#`
System Variable	Name	`performance_schema_max_file_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`50`

The maximum number of file instruments.

performance_schema_max_file_handles

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_file_handles=#`
System Variable	Name	`performance_schema_max_file_handles`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`32768`

The maximum number of opened file objects.

The value of performance_schema_max_file_handles should be greater than the value of open_files_limit: open_files_limit affects the maximum number of open file handles the server can support and performance_schema_max_file_handles affects how many of these file handles can be instrumented.

performance_schema_max_file_instances

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_file_instances=#`
System Variable	Name	`performance_schema_max_file_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`10000`

The maximum number of instrumented file objects.

performance_schema_max_mutex_classes

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_mutex_classes=#`
System Variable	Name	`performance_schema_max_mutex_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`200`

The maximum number of mutex instruments.

performance_schema_max_mutex_instances

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_mutex_instances=#`
System Variable	Name	`performance_schema_max_mutex_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`1000`

The maximum number of instrumented mutex objects.

performance_schema_max_rwlock_classes

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_rwlock_classes=#`
System Variable	Name	`performance_schema_max_rwlock_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.5.6)	Type	integer
	Default	`20`
Permitted Values (>= 5.5.7)	Type	integer
	Default	`30`

The maximum number of rwlock instruments.

performance_schema_max_rwlock_instances

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_rwlock_instances=#`
System Variable	Name	`performance_schema_max_rwlock_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`1000`

The maximum number of instrumented rwlock objects.

performance_schema_max_table_handles

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_table_handles=#`
System Variable	Name	`performance_schema_max_table_handles`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`100000`

The maximum number of opened table objects.

performance_schema_max_table_instances

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_table_instances=#`
System Variable	Name	`performance_schema_max_table_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`50000`

The maximum number of instrumented table objects.

performance_schema_max_thread_classes

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_thread_classes=#`
System Variable	Name	`performance_schema_max_thread_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`50`

The maximum number of thread instruments.

performance_schema_max_thread_instances

Introduced	5.5.3
Command-Line Format	`--performance_schema_max_thread_instances=#`
System Variable	Name	`performance_schema_max_thread_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	integer
	Default	`1000`

The maximum number of instrumented thread objects. The value controls the size of the threads table. If this maximum is exceeded such that a thread cannot be instrumented, the Performance Schema increments the Performance_schema_thread_instances_lost status variable.

The max_connections and max_delayed_threads system variables affect how many threads are run in the server. performance_schema_max_thread_instances affects how many of these running threads can be instrumented. If you increase max_connections or max_delayed_threads, you should consider increasing performance_schema_max_thread_instances so that performance_schema_max_thread_instances is greater than the sum of max_connections and max_delayed_threads.

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