Translated slides from my seminar about using Performance Schema for MySQL troubleshooting at Devconf 2013

1. <Insert Picture Here>
Performance Schema for MySQL troubleshooting
Sveta Smirnova
Senior Principal Technical MySQL Support Engineer

2. Content
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History of Performance Schema
Tables for DBA
Tables for developers
Other tables
Tools
Performance and tests
Options
Information sources
Conclusion

3. History of Performance Schema
•
•
•
•
First version: in MySQL 5.5
17 tables
Useful mostly for developers of MySQL code
Tools for
– Mutexes
– Locks
• Required good knowledge of MySQL code

4. Kinds of tables
• Settings
– _setup
– _instances
• Events
– events_waits_
• Digests
• History
• Other

5. Version 5.6 turned its face to DBA
• More features
• 52 tables
• New tables, very useful
for DBA
• Knowledge of MySQL
source code is not a
requirement anymore
*That's me talking at Devconf 2012 about how I am,
as MySQL Support engineer,
is happy with new features in Performance Schema
*

6. Tables for DBA
• events_statements_*
• events_stages_*
• Connection

7. events_statements_*
• Statements
– statement/sql
• statement/sql/delete
• statement/sql/select
• Commands
– COM_PING, COM_QUIT, ...
– statement/com
• statement/com/Ping
• statement/com/Quit
• Errors
– statement/sql/error
– statement/com/Error

8. events_statements_*:
which queries finished with an error
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mysql> select THREAD_ID, substr(SQL_TEXT, 1, 20),
MYSQL_ERRNO from events_statements_history_long where
MYSQL_ERRNO != 0;
+­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­+
| THREAD_ID | substr(SQL_TEXT, 1, 20) | MYSQL_ERRNO |
+­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­+
| 18 | select from * event_ | 1064 |
| 18 | select * from event | 1146 |
| 18 | select * from event | 1146 |
| 18 | select THREAD_ID, SQ | 1146 |
+­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­+
4 rows in set (0.00 sec)

9. events_statements_*:
queries which need to be optimized
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mysql> select THREAD_ID as TID, substr(SQL_TEXT, 1, 20)
as SQL_TEXT, ROWS_SENT as RS, ROWS_EXAMINED as RE from
events_statements_history_long where ROWS_EXAMINED >
ROWS_SENT * 10 limit 5;
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| TID | SQL_TEXT | RS | RE |
+­­­­­+­­­­­­­­­­­­­­­­­­­­­­+­­­­+­­­­­+
| 18 | select THREAD_ID, SQ | 4 | 147 |
| 18 | select THREAD_ID, su | 4 | 148 |
| 18 | select THREAD_ID, su | 4 | 152 |
| 18 | select THREAD_ID, su | 4 | 153 |
| 18 | select THREAD_ID, su | 1 | 154 |
+­­­­­+­­­­­­­­­­­­­­­­­­­­­­+­­­­+­­­­­+
5 rows in set (0.00 sec)

10. events_statements_*: what also is worth attention
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CREATED_TMP_DISK_TABLES
CREATED_TMP_TABLES
SELECT_FULL_JOIN
SELECT_RANGE_CHECK
SELECT_SCAN
SORT_MERGE_PASSES
SORT_SCAN
NO_INDEX_USED
NO_GOOD_INDEX_USED

11. events_statements_*: ps_helper view
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http://www.markleith.co.uk/ps_helper/
View: statement_analysis
View: statements_with_runtimes_in_95th_percentile
View: statements_with_temp_tables
View: statements_with_sorting
View: statements_with_full_table_scans
View: statements_with_errors_or_warnings

12. event_stages_*
• Same information which you see in table
INFORMATION_SCHEMA.PROCESSLIST or SHOW
PROCESSLIST output
–
–
–
–
init
executing
Opening tables
...
• Replacement of SHOW PROFILE
• Only server-level
• No information from storage engine in this table!

13. event_stages_*:
«Sending data» for more than 10 seconds
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mysql> select events_stages_history_long.event_name,
sql_text,
events_stages_history_long.timer_wait/1000000000000
wait_s from events_stages_history_long join
events_statements_history_long on
(events_stages_history_long.nesting_event_id =
events_statements_history_long.event_id) where
events_stages_history_long.EVENT_NAME like '%Sending
data' and rows_sent < 10000000 and
events_stages_history_long.timer_wait > 10*1000000000000
order by events_stages_history_long.timer_wait descG
************************ 1. row ************************
event_name: stage/sql/Sending data
sql_text: insert into test.t2 select * from test.t2
wait_s: 243.5235
1 rows in set (0.01 sec)

14. event_stages_*:
other operations which can run slow
• Everything, related to temporary tables
– EVENT_NAME LIKE 'stage/sql/%tmp%'
• Everything, related to locks
– EVENT_NAME LIKE 'stage/sql/%lock%'
• Everything in state «Waiting for»
– EVENT_NAME LIKE 'stage/%/Waiting for%'
• Frequently met issues (from my Support experience)
–
–
–
–
–
EVENT_NAME='stage/sql/end'
EVENT_NAME='stage/sql/freeing items'
EVENT_NAME='stage/sql/Sending data'
EVENT_NAME='stage/sql/cleaning up'
EVENT_NAME='stage/sql/closing tables'

15. event_stages_*: longest queries
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mysql> select eshl.event_name, sql_text,
eshl.timer_wait/1000000000000 wait_s from
events_stages_history_long eshl join
events_statements_history_long esthl on
(eshl.nesting_event_id = esthl.event_id) where
eshl.timer_wait > 10*1000000000000G
************************ 1. row ************************
event_name: stage/sql/copy to tmp table
sql_text: alter table t2 engine=innodb
wait_s: 186.8122
************************ 2. row ************************
event_name: stage/sql/Waiting for table metadata lock
sql_text: insert into t2 select * from t2 LIMIT 10
wait_s: 46.6250
2 rows in set (0.01 sec)

16. event_stages_*: joins
• NESTING_EVENT_ID
– Statement
– Wait
– Stage
• EVENT_ID
events_statements
EVENT_ID
events_stages
NESTING_EVENT_ID
events_stages
NESTING_EVENT_ID
events_stages
NESTING_EVENT_ID

17. Connection Tables: accounts
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mysql> select user, host, current_connections as cur,
total_connections as total from accounts;
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| user | host | cur | total |
+­­­­­­+­­­­­­­­­­­+­­­­­+­­­­­­­+
| foo | localhost | 0 | 3 |
| root | localhost | 1 | 3 |
| NULL | NULL | 14 | 17 |
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3 rows in set (0.01 sec)

18. Connection Tables: users, hosts
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mysql> select user, current_connections as cur,
total_connections as total from users;
+­­­­­­+­­­­­+­­­­­­­+
| user | cur | total |
+­­­­­­+­­­­­+­­­­­­­+
| root | 1 | 3 |
| NULL | 14 | 17 |
| foo | 0 | 3 |
+­­­­­­+­­­­­+­­­­­­­+
3 rows in set (0.00 sec)
mysql> select host, current_connections as cur,
total_connections as total from hosts;
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| host | cur | total |
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| NULL | 14 | 17 |
| localhost | 1 | 6 |
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2 rows in set (0.01 sec)

19. Connection Attribute Tables
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mysql_init(&mysql);
mysql_options(&mysql,MYSQL_OPT_CONNECT_ATTR_RESET, 0);
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mysql_options4(&mysql,MYSQL_OPT_CONNECT_ATTR_ADD,
"program", "Devconf2013");
mysql_options4(&mysql,MYSQL_OPT_CONNECT_ATTR_ADD,
"author", "Sveta Smirnova");
mysql_options4(&mysql,MYSQL_OPT_CONNECT_ATTR_ADD,
"session", "MySQL Performance Schema");
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mysql_real_connect(&mysql, "127.0.0.1", "root", "",
"test", 13000, NULL, 0);

20. Connection Attribute Tables
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mysql> select ATTR_NAME, ATTR_VALUE from
performance_schema.session_account_connect_attrs where
processlist_id != @@pseudo_thread_id;
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| ATTR_NAME | ATTR_VALUE |
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| _os | Linux |
| _client_name | libmysql |
| _pid | 4729 |
| program_name | Devconf2013 |
| _platform | x86_64 |
| session | MySQL Performance Schema |
| author | Sveta Smirnova |
| _client_version | 5.6.12 |
+­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­­+
8 rows in set (0.01 sec)

21. Connection Attribute Tables: foreigners prohibited!
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mysql> select PROCESSLIST_ID as PID, ATTR_NAME,
ATTR_VALUE from session_account_connect_attrs where
attr_name='program_name';
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| PID | ATTR_NAME | ATTR_VALUE |
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| 9 | program_name | mysql |
| 13 | program_name | Devconf2013 |
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2 rows in set (0.00 sec)

22. Connection Attribute Tables: foreigners prohibited!
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mysql> select PROCESSLIST_ID as PID, ATTR_NAME,
ATTR_VALUE from session_account_connect_attrs where
attr_name='program_name' union select PROCESSLIST_ID as
PID, 'program_name' as ATTR_NAME,
sum(if(attr_name='program_name', 1, 0)) as ATTR_VALUE
from session_account_connect_attrs group by
processlist_id having(ATTR_VALUE=0);
+­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­+
| PID | ATTR_NAME | ATTR_VALUE |
+­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­+
| 9 | program_name | mysql |
| 13 | program_name | Devconf2013 |
| 21 | program_name | 0 |
+­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­+
3 rows in set (0.01 sec)

23. host_cache
• Content of DNS cache
• Errors from
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Name server
Connection
Authentication
max_connect_errors, max_user_errors, etc.
• Your first assistant in case of connection issue

24. threads
• Two kinds of THREADS
– Background
– Foreground
• Fields
– THREAD_ID
• Internal thread id
– PROCESSLIST_ID
• id, observable in the SHOW PROCESSLIST output
– NAME
• Instrument
– PARENT_THREAD_ID
• Internal id of the parent thread
– PROCESSLIST_*
• Only for для FOREGROUND threads

25. threads
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mysql> select * from threads where type = 'foreground'G
************************ 1. row ************************
THREAD_ID: 16
NAME: thread/sql/one_connection
TYPE: FOREGROUND
PROCESSLIST_ID: 1
PROCESSLIST_USER: root
PROCESSLIST_HOST: localhost
PROCESSLIST_DB: performance_schema
PROCESSLIST_COMMAND: Query
PROCESSLIST_TIME: 0
PROCESSLIST_STATE: Sending data
PROCESSLIST_INFO: select * from threads where type =
'foreground'
PARENT_THREAD_ID: 1
ROLE: NULL
INSTRUMENTED: YES
1 row in set (0.00 sec)

26. threads
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mysql> select name from threads where type='background';
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| name |
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| thread/sql/main |
| thread/innodb/io_handler_thread |
| thread/innodb/io_handler_thread |
| thread/innodb/io_handler_thread |
| thread/innodb/io_handler_thread |
| thread/innodb/io_handler_thread |
| thread/innodb/io_handler_thread |
| thread/innodb/srv_lock_timeout_thread |
| thread/innodb/srv_error_monitor_thread |
| thread/innodb/srv_monitor_thread |
| thread/innodb/srv_master_thread |
| thread/innodb/srv_purge_thread |
| thread/innodb/page_cleaner_thread |
| thread/sql/signal_handler |
+­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­+
14 rows in set (0.00 sec)

27. events_waits_*
• EVENT_NAME
– wait/synch/rwlock/innodb/dict_operation_lock
• SOURCE
– Line of the source code
• OPERATION
– Kind of operation: read, lock, write

28. event_waits_*
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mysql> select e.EVENT_NAME, e.SOURCE, e.OPERATION,
t.PROCESSLIST_INFO from events_waits_current e join
threads t using(thread_id) where type='foreground' and
processlist_id != 1G
************************ 1. row ************************
EVENT_NAME:
wait/synch/cond/sql/Item_func_sleep::cond
SOURCE: item_func.cc:4212
OPERATION: timed_wait
PROCESSLIST_INFO: select sleep(100) from t1
1 row in set (0.01 sec)

29. wait/synch/cond/sql/Item_func_sleep::cond
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$ cat ­n sql/item_func.cc | head ­n 4220 | tail ­n 35
4186
4187 /**
4188 Wait for a given condition to be signaled.
4189
4190 @param cond The condition variable to wait on.
4191 @param mutex The associated mutex.
4192
4193 @remark The absolute timeout is preserved across
calls.
4194
4195 @retval return value from mysql_cond_timedwait
4196 */
4197

30. wait/synch/cond/sql/Item_func_sleep::cond
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4198 int Interruptible_wait::wait(mysql_cond_t
*cond, mysql_mutex_t *mutex)
4199 {
4200 int error;
4201 struct timespec timeout;
4202
4203 while (1)
4204 {
4205 /* Wait for a fixed interval. */
4206 set_timespec_nsec(timeout,
m_interrupt_interval);
4207
4208 /* But only if not past the absolute
timeout. */
4209 if (cmp_timespec(timeout, m_abs_timeout) > 0)
4210 timeout= m_abs_timeout;

31. wait/synch/cond/sql/Item_func_sleep::cond
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4212 error= mysql_cond_timedwait(cond, mutex,
&timeout);
4213 if (error == ETIMEDOUT || error == ETIME)
4214 {
4215 /* Return error if timed out or connection
is broken. */
4216 if (!cmp_timespec(timeout, m_abs_timeout) ||
!m_thd­>is_connected())
4217 break;
4218 }
4219 /* Otherwise, propagate status to the caller.
*/
4220 else

32. Query statistics
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mysql> UPDATE performance_schema.threads SET
instrumented = 'NO';
Query OK, 15 rows affected (0.04 sec)
Rows matched: 15 Changed: 15 Warnings: 0
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Open new connection
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mysql> truncate events_waits_history_long;
Query OK, 0 rows affected (0.00 sec)
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In new connection
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mysql2> create temporary table norepl_t1 engine=myisam
select amount, price, money, id_product from test;
Query OK, 262144 rows affected (4.76 sec)
Records: 262144 Duplicates: 0 Warnings: 0

33. Query events_waits_history_long
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mysql> select e.EVENT_NAME, e.SOURCE, e.OPERATION,
count(*) as cnt from events_waits_history_long e join
threads t using(thread_id) where type='foreground' and
processlist_id not in (1, @@pseudo_thread_id) group by
e.EVENT_NAME, e.SOURCE, e.OPERATION order by cnt descG
************************ 1. row ************************
EVENT_NAME: wait/synch/mutex/innodb/lock_mutex
SOURCE: lock0lock.cc:5529
OPERATION: lock
cnt: 1428
************************ 2. row ************************
EVENT_NAME: wait/synch/mutex/innodb/lock_mutex
SOURCE: lock0lock.cc:6362
OPERATION: lock
cnt: 1428

34. Query events_waits_history_long
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************************ 3. row ************************
EVENT_NAME: wait/synch/mutex/innodb/trx_sys_mutex
SOURCE: lock0lock.cc:5530
OPERATION: lock
cnt: 1428
************************ 4. row ************************
EVENT_NAME: wait/synch/mutex/innodb/trx_mutex
SOURCE: lock0lock.cc:2133
OPERATION: lock
cnt: 1423
************************ 5. row ************************
EVENT_NAME: wait/io/table/sql/handler
SOURCE: handler.cc:2627
OPERATION: fetch
cnt: 1423

35. Query events_waits_history_long
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************************ 6. row ************************
EVENT_NAME: wait/synch/mutex/innodb/lock_mutex
SOURCE: lock0lock.cc:6050
OPERATION: lock
cnt: 1421
************************ 7. row ************************
EVENT_NAME: wait/synch/mutex/innodb/trx_sys_mutex
SOURCE: trx0sys.ic:431
OPERATION: lock
cnt: 1421
************************ 8. row ************************
EVENT_NAME: wait/synch/mutex/innodb/buf_pool_mutex
SOURCE: buf0buf.ic:887
OPERATION: lock
Cnt: 6
...

36. Which kind of events can we examine?
• setup_instruments.NAME
– wait/io/file
• Operations with files
– wait/io/socket
– wait/io/table/sql/handler
– wait/lock/table/sql/handler
– wait/synch/cond
• InnoDB, MyISAM, sql
– wait/synch/mutex
• sql, mysys, storage engines
– wait/synch/rwlock/
• sql, InnoDB, MyISAM

37. ps_helper
• All VIEWs work for MySQL 5.5
–
–
–
–
–
–
–
latest_file_io
top_io_by_file
top_io_by_thread
top_global_consumers_by_avg_latency
top_global_consumers_by_total_latency
top_global_io_consumers_by_latency
top_global_io_consumers_by_bytes_usage
• There are few views for 5.6 which use digest tables

38. *_instances tables
• file_instances
– Opened files
• socket_instances
– Connections
• cond_instances
• rwlock_instances
– select * from rwlock_instances where
READ_LOCKED_BY_COUNT > 0;
– select * from rwlock_instances where
WRITE_LOCKED_BY_THREAD_ID > 0;
• mutex_instances
– LOCKED_BY_THREAD_ID

39. Digests
•
•
•
•
•
•
•
•
events_stages_*
events_statements_*
events_waits_*
file_*
objects_*
socket_*
table_io_waits_*
table_lock_waits_*

40. Digests: events_stages_summary_*
• events_stages_summary_by_account_by_event_name
– Helps to find an account which performs problematic queries
• events_stages_summary_by_host_by_event_name
• events_stages_summary_by_user_by_event_name
– Same, but sorted by host and user name
• events_stages_summary_by_thread_by_event_name
– Easy to find out what makes troubles on your server right now
– Since statistics is saved for some time you can find it and after the
problem stopped to show up
• events_stages_summary_by_global_by_event_name
– Global stats by event name
– Does not indicate user, host, account and thread

41. •
•
•
•
•
Digests: events_statements_summary_*
events_statements_summary_by_account_by_event_name
events_statements_summary_by_host_by_event_name
events_statements_summary_by_user_by_event_name
events_statements_summary_by_thread_by_event_name
events_statements_summary_global_by_event_name
– Same as stages, but stats are taken from tables events_statements_*
• events_statements_summary_by_digest
– Stats by digest field:
• 42b93d481e96b9c9b4049b9407900194
• Query written as SELECT fname FROM tname WHERE fname = ?
– For example, you can find all statements which create temporary tables by
querying this table

42. Digests: events_waits_summary_*
•
•
•
•
•
events_waits_summary_by_account_by_event_name
events_waits_summary_by_host_by_event_name
events_waits_summary_by_thread_by_event_name
events_waits_summary_by_user_by_event_name
events_waits_summary_global_by_event_name
– Similar to events_stages_* digests
• events_waits_summary_by_instance
– By OBJECT_INSTANCE_BEGIN field

43. Other digests
• file_summary_by_event_name
– Does not show file name!
•
•
•
•
•
file_summary_by_instance
objects_summary_global_by_type
socket_summary_by_event_name
socket_summary_by_event_name
socket_summary_by_instance
– By OBJECT_INSTANCE_BEGIN field
• table_io_waits_summary_by_index_usage
• table_io_waits_summary_by_table
• table_lock_waits_summary_by_table

44. Digests
• WHERE COUNT_STAR > 0
• Sort or query by an operation you are interested in
• Sort by COUNT_STAR

45. Performance

46. Performance: version 5.5
• Performance Schema is OFF by default
• Noticeable performance issues
– Up to 7% in case of RO load
– Up to 20% in case of RW load
– Numbers based on tests by Dimitri Kravtchuk
(http://dimitrik.free.fr/blog/archives/2010/05/mysql-performance-using-performance-schema.html )
• No performance loss if turned off

47. Performance: version 5.6
• Performance Schema is ON by default
• Performance loss can happen, but not big
– Not more than 5% for most setups, likely near 0
– Maximum up to 10% in case if all instrumentations are turned ON
– Numbers based on tests by Dimitri Kravtchuk
(http://dimitrik.free.fr/blog/archives/2012/06/mysql-performance-pfs-overhead-in-56.html)
• global_instrumentation
– Minimal overhead
• Detailed instrumentation
– Noticeable overhead
• History tables
– minimal overhead

48. How P_S uses OS and hardware resources
• Memory
–
–
–
–
Allocated at the server startup
Freed when MySQL server is stopped
Uses arrays instead of linked lists
mysql> show engine performance_schema status;
+­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­+
| Type | Name | Status |
+­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­+
...
| performance_schema | performance_schema.memory | 68024616 |
+­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­+
• CPU
– Depends from number of instruments
– More instruments — higher load

49. Options

50. What, where and when to setup
• At compile time
• At the server startup
– Options in my.cnf
– All options are static
• Runtime
– setup_* tables
• What can you tune?
– Look for tables documentation

51. Configuration options
• performance_schema = ON|OFF
– Is it On or Off?
• performance_schema_%_size
– Size of history tables
– Size of instrumented objects
• performance_schema_max_%_classes
– Maximum number of cond|fle|io|% instruments
• performance_schema_max_%_instances
– Maximum number of cond|fle|io|% objects

52. Configuration options
• performance_schema_consumer_TABLE_NAME
– performance_schema_consumer_events_stages_current
– performance_schema_consumer_events_waits_current
– ...
• Turns instrumentations On of Off
– OFF, FALSE, 0
– ON, TRUE, 1
• setup_consumers table
– update setup_consumers set enabled='no'
where name='events_stages_current';

53. Tables setup_actors and setup_objects
• setup_actors
–
–
–
–
Which user threads to monitor
DELETE , then INSERT
UPDATE not allowed
insert into setup_actors values('%', 'sveta', '%');
• Only for user sveta
• setup_objects
– Which objects to monitor
– update setup_objects set enabled='no'
where object_schema='%';
– insert into setup_objects values
('TABLE', 'test', 't1', 'YES', 'YES');

54. •
•
•
•
setup_instruments table
Detailed setup of instruments
549 instruments in the standard distribution*
update setup_instruments set enabled='no';
update setup_instruments set enabled='yes'
where name like 'statement%';
*Written at June, 2013. Subject to change.

55. Timers
●
●
Values for your machine
●
●
●
●
●
●
●
●
●
●
●
●
mysql> select * from performance_timers;
+­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+
| TIMER_NAME | TIMER_FREQUENCY | TIMER_RESOLUTION | TIMER_OVERHEAD |
+­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+
| CYCLE | 2592796019 | 1 | 18 |
| NANOSECOND | 1000000000 | 1 | 45 |
| MICROSECOND | 1000000 | 1 | 48 |
| MILLISECOND | 1037 | 1 | 54 |
| TICK | 103 | 1 | 547 |
+­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+
5 rows in set (0.00 sec)
●
●
●
●
How to tune:
mysql> update setup_timers set timer_name='tick'
where name = 'stage';

56. What happens inside Performance Schema?
●
●
●
●
●
●
●
●
●
●
mysql> show global status like 'perf%';
+­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­
+
| Variable_name | Value
|
+­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­
+
| Performance_schema_accounts_lost | 0
|
| Performance_schema_cond_classes_lost | 0
|
| Performance_schema_cond_instances_lost | 0
|
| Performance_schema_digest_lost | 0
|
...
●
●
If Value is not null — your *_size options are too small

57. •
•
•
•
•
What happens inside Performance Schema?
SHOW ENGINE PERFORMANCE_SCHEMA STATUS;
Contains information about memory usage
Table_name.attribute
(Internal_buffer).attribute
*.size, *.row_size
– Not-configurable, for example, size of a table row
• *.count, *.row_count
– Configurable with help of options
• *.memory
– size * count
– events_waits_history_long.memory
– performance_schema.memory

58. Where to find information?
• http://www.markleith.co.uk/ps_helper/
• http://www.drdobbs.com/database/detailed-profiling-of-sql-activity-in-my/240154959
• http://marcalff.blogspot.ru
• http://dimitrik.free.fr/blog/
• http://dev.mysql.com/doc/refman/5.6/en/performance-schema.html

59. Conclusion
• Performance schema — wonderful tool for a DBA
when she needs to troubleshoot performance issue
• You can configure it online: without server restart
• Allows very detailed setup
• Always tune it for your own needs!
• Don't instrument everything: use it for operations you
are interested in only

60. ?

61. THANK YOU!

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product direction. It is intended for information
purposes only, and may not be incorporated into any
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