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

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

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Performance Schema for MySQL troubleshooting Performance Schema for MySQL troubleshooting Presentation Transcript

  • <Insert Picture Here> Performance Schema for MySQL troubleshooting Sveta Smirnova Senior Principal Technical MySQL Support Engineer
  • Content • • • • • • • • • History of Performance Schema Tables for DBA Tables for developers Other tables Tools Performance and tests Options Information sources Conclusion
  • 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
  • Kinds of tables • Settings – _setup – _instances • Events – events_waits_ • Digests • History • Other
  • 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 *
  • Tables for DBA • events_statements_* • events_stages_* • Connection
  • 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
  • events_statements_*: which queries finished with an error ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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)
  • events_statements_*: queries which need to be optimized ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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; +­­­­­+­­­­­­­­­­­­­­­­­­­­­­+­­­­+­­­­­+ | 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)
  • events_statements_*: what also is worth attention • • • • • • • • • 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
  • events_statements_*: ps_helper view • • • • • • • 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
  • 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!
  • event_stages_*: «Sending data» for more than 10 seconds ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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)
  • 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'
  • event_stages_*: longest queries ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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)
  • 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
  • Connection Tables: accounts ● ● ● ● ● ● ● ● ● ● ● ● mysql> select user, host, current_connections as cur,  total_connections as total from accounts; +­­­­­­+­­­­­­­­­­­+­­­­­+­­­­­­­+ | user | host      | cur | total | +­­­­­­+­­­­­­­­­­­+­­­­­+­­­­­­­+ | foo  | localhost |   0 |     3 | | root | localhost |   1 |     3 | | NULL | NULL      |  14 |    17 | +­­­­­­+­­­­­­­­­­­+­­­­­+­­­­­­­+ 3 rows in set (0.01 sec)
  • Connection Tables: users, hosts ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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; +­­­­­­­­­­­+­­­­­+­­­­­­­+ | host      | cur | total | +­­­­­­­­­­­+­­­­­+­­­­­­­+ | NULL      |  14 |    17 | | localhost |   1 |     6 | +­­­­­­­­­­­+­­­­­+­­­­­­­+ 2 rows in set (0.01 sec)
  • Connection Attribute Tables ● ● ● mysql_init(&mysql); mysql_options(&mysql,MYSQL_OPT_CONNECT_ATTR_RESET, 0); ● ● ● ● ● ● ● ● 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"); ● ● ● ● mysql_real_connect(&mysql, "127.0.0.1", "root", "", "test", 13000, NULL, 0);
  • Connection Attribute Tables ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● mysql> select ATTR_NAME, ATTR_VALUE from  performance_schema.session_account_connect_attrs where  processlist_id != @@pseudo_thread_id; +­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­­+ | ATTR_NAME       | ATTR_VALUE               | +­­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­­­­­­­­­­+ | _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)
  • Connection Attribute Tables: foreigners prohibited! ● ● ● ● ● ● ● ● ● ● ● mysql> select PROCESSLIST_ID as PID, ATTR_NAME,  ATTR_VALUE from session_account_connect_attrs where  attr_name='program_name'; +­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­+ | PID | ATTR_NAME    | ATTR_VALUE  | +­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­+ |   9 | program_name | mysql       | |  13 | program_name | Devconf2013 | +­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­+ 2 rows in set (0.00 sec)
  • Connection Attribute Tables: foreigners prohibited! ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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)
  • host_cache • Content of DNS cache • Errors from – – – – Name server Connection Authentication max_connect_errors, max_user_errors, etc. • Your first assistant in case of connection issue
  • 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
  • threads ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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)
  • threads ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● mysql> select name from threads where type='background'; +­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­+ | name                                   | +­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­+ | 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)
  • events_waits_* • EVENT_NAME – wait/synch/rwlock/innodb/dict_operation_lock • SOURCE – Line of the source code • OPERATION – Kind of operation: read, lock, write
  • event_waits_* ● ● ● ● ● ● ● ● ● ● ● ● ● 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)
  • wait/synch/cond/sql/Item_func_sleep::cond ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● $ 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
  • wait/synch/cond/sql/Item_func_sleep::cond ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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;
  • wait/synch/cond/sql/Item_func_sleep::cond ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●    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
  • Query statistics ● ● ● ● ● mysql> UPDATE performance_schema.threads SET  instrumented = 'NO';  Query OK, 15 rows affected (0.04 sec) Rows matched: 15  Changed: 15  Warnings: 0 ● ● Open new connection ● ● mysql> truncate events_waits_history_long;                                                                                                                                Query OK, 0 rows affected (0.00 sec) ● ● In new connection ● ● ● ● ● 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
  • Query events_waits_history_long ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 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
  • Query events_waits_history_long ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ************************ 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
  • Query events_waits_history_long ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ************************ 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 ...
  • 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
  • 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
  • *_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
  • Digests • • • • • • • • events_stages_* events_statements_* events_waits_* file_* objects_* socket_* table_io_waits_* table_lock_waits_*
  • 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
  • • • • • • 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
  • 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
  • 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
  • Digests • WHERE COUNT_STAR > 0 • Sort or query by an operation you are interested in • Sort by COUNT_STAR
  • Performance
  • 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
  • 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
  • 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
  • Options
  • 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
  • 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
  • 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';
  • 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');
  • • • • • 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.
  • 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';
  • 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
  • • • • • • 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
  • 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
  • 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
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