PERFORMANCE_SCHEMA 详解
mysql 是否支持 performance_schema 引擎
mysql> SELECT * FROM INFORMATION_SCHEMA.ENGINES ;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| ENGINE | SUPPORT | COMMENT | TRANSACTIONS | XA | SAVEPOINTS |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
mysql服务器启用 performance_schema
my.cnf文件中
[mysqld]
performance_schema=ON
mysql> SHOW VARIABLES LIKE 'performance_schema';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| performance_schema | ON |
+--------------------+-------+
1 row in set (0.11 sec)
Performance Schema Instrument命名规则
最上层的instrument组件
-
idle
idle instrument 组件 idle event描述来自：socket_instances.STATE 列： Section 22.9.3.5, “The socket_instances Table”. -
stage
stage instrument 组件 组成形式： stage/code_area/stage_name ， code_area 一般是sql or myisam。 stage name 一般来自： SHOW PROCESSLIST，如：Sorting result ，Sending data -
statement
Statement instrument 组件 statement/abstract/* ： 一般都是早期的stage，在抽象sql都还没来得及解析的时候。 statement/com: SQL 命令操作 如：statement/com/Connect statement/sql： SQL语句操作 如：statement/sql/create_db -
wait
Wait Instrument 组件 wait/io ： IO 等待事件 wait/io/file ： 文件IO等待事件。等待文件操作完成的时间如：fwrite().但是物理IO有可能因为缓存的原因调用fwrite时不会写磁盘。 wait/io/socket： socket相关的IO等待 wait/io/table ： 表相关的IO等待。一般对于记录rows来说有fetch，insert，update，delete四种操作。 不像其他等待事件，table I/O 还包含了其他的等待事件。 比如：table io可能包含了文件IO和内存IO。因为读取table rows的时候，有可能会去从文件读取数据。 * wait/lock: * wait/lock/table ： 表操作的锁等待事件 * wait/synch: * wait/synch/cond ：condition就是线程与线程之间的信号。 * wait/synch/mutex ： mutex主要用来锁住一块共享资源。 * wait/synch/rwlock ： 读写锁
收集所有的事件:
instrument 和 consumer 都会被enable ， 所以一开始他们不会收集所有的事件。
为了让他们都enable 或者 enable event timing。
执行以下两条语句:
mysql> UPDATE setup_instruments SET ENABLED = 'YES', TIMED = 'YES';
Query OK, 338 rows affected (0.12 sec)
mysql> UPDATE setup_consumers SET ENABLED = 'YES';
Query OK, 8 rows affected (0.00 sec)
events_waits_history & events_waits_history_long 记录了每个thread最近10条和10000条event。
SELECT EVENT_ID, EVENT_NAME, TIMER_WAIT FROM events_waits_history WHERE THREAD_ID =21 ORDER BY EVENT_ID;
summary 表提供了整个时间段的一些统计信息。他们统计事件的处理方式和之前都不一样。如果想知道某个instrument 被执行的最频繁，或者发生的频率非常高，可以通过排序 events_waits_summary_global_by_event_name表，根据 COUNT_STAR 或者 SUM_TIMER_WAIT列。mysql> SELECT EVENT_NAME, COUNT_STAR FROM events_waits_summary_global_by_event_name ORDER BY COUNT_STAR DESC LIMIT 10;
+--------------------------------------+------------+
| EVENT_NAME | COUNT_STAR |
+--------------------------------------+------------+
| wait/io/file/sql/FRM | 1682 |
| wait/io/file/innodb/innodb_data_file | 596 |
| idle | 204 |
| wait/io/file/sql/binlog | 170 |
| wait/io/file/myisam/kfile | 110 |
| wait/io/file/myisam/dfile | 90 |
| wait/io/file/sql/binlog_index | 47 |
| wait/io/file/innodb/innodb_log_file | 18 |
| wait/io/file/sql/dbopt | 14 |
| wait/io/file/sql/casetest | 10 |
+--------------------------------------+------------+
10 rows in set (0.31 sec)
mysql> SELECT EVENT_NAME, SUM_TIMER_WAIT FROM events_waits_summary_global_by_event_name ORDER BY SUM_TIMER_WAIT DESC LIMIT 10;
+--------------------------------------+-------------------+
| EVENT_NAME | SUM_TIMER_WAIT |
+--------------------------------------+-------------------+
| idle | 20173041031000000 |
| wait/io/file/innodb/innodb_data_file | 666638377892 |
| wait/io/file/sql/dbopt | 177140672226 |
| wait/io/file/sql/FRM | 91152018924 |
| wait/io/file/sql/binlog | 43352476474 |
| wait/io/file/innodb/innodb_log_file | 35962857780 |
| wait/io/file/sql/binlog_index | 20679496964 |
| wait/io/file/myisam/kfile | 16840088732 |
| wait/io/file/sql/ERRMSG | 8064330196 |
| wait/io/file/myisam/dfile | 4785274304 |
+--------------------------------------+-------------------+
10 rows in set (0.03 sec)
setup表用来配置和显示监控信息的。 例如：什么样的timer 被使用，请查询setup_timersmysql> SELECT * FROM setup_timers;
+-----------+-------------+
| NAME | TIMER_NAME |
+-----------+-------------+
| idle | MICROSECOND |
| wait | CYCLE |
| stage | NANOSECOND |
| statement | NANOSECOND |
+-----------+-------------+
4 rows in set (0.00 sec)
setup_instruments 列出了哪些event会被收集与监控：mysql> SELECT * FROM setup_instruments limit 10;
+-------------------------------------------------------+---------+-------+
| NAME | ENABLED | TIMED |
+-------------------------------------------------------+---------+-------+
| wait/synch/mutex/sql/PAGE::lock | YES | YES |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_sync | YES | YES |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_active | YES | YES |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_pool | YES | YES |
| wait/synch/mutex/sql/LOCK_des_key_file | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_commit | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_commit_queue | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_done | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_flush_queue | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_index | YES | YES |
+-------------------------------------------------------+---------+-------+
10 rows in set (0.00 sec)
哪些event是不是instrument，可以给enabled设置yes or no
mysql> UPDATE setup_instruments SET ENABLED = 'NO' WHERE NAME = 'wait/synch/mutex/sql/LOCK_mysql_create_db';
Query OK, 0 rows affected (0.01 sec)
Rows matched: 0 Changed: 0 Warnings: 0
消费者:接收EVENTS 的表
performance schema 使用收集的events 来更新performance_schema 数据库的那些表，这些表扮演着事件信息消费者的角色。setup_consumers 列出了可用的消费者 以及哪些是enabled.mysql> SELECT * FROM setup_consumers;
+--------------------------------+---------+
| NAME | ENABLED |
+--------------------------------+---------+
| events_stages_current | YES |
| events_stages_history | YES |
| events_stages_history_long | YES |
| events_statements_current | YES |
| events_statements_history | YES |
| events_statements_history_long | YES |
| events_waits_current | YES |
| events_waits_history | YES |
| events_waits_history_long | YES |
| global_instrumentation | YES |
| thread_instrumentation | YES |
| statements_digest | YES |
MySQL在5.6版本中包含了一个强大的特性——performance-schema
合理的使用这个数据库中的表，能为我们解决一些瓶颈问题提供帮助，但是在我使用的5.6.21版本中，已经包含了52张表，后续还有可能会持续增加，所以搞清楚各个表之间的关系很重要。
mysql> show tables like '%setup%';
+----------------------------------------+
| Tables_in_performance_schema (%setup%) |
+----------------------------------------+
| setup_actors |
| setup_consumers |
| setup_instruments |
| setup_objects |
| setup_timers |
+----------------------------------------+
5 rows in set (0.01 sec)
1)setup_instruments [测量仪器]
使用performance-schema诊断问题的过程类似于医生给病人看病的过程。"setup_instruments"犹如医生能够使用的测量仪器（比如温度计，CT，X光等），在MySQL的官方文档中，使用“instrument”一词来表示，这应该也是这个表的名称的来源。这个表的每一行代表一个"instrument","instrument"在MySQL的源码中表示为一段为了测量相应指标的代码。这张表的三个字段分别为“name enabled timed”,enabled表示是否启用该"instrument", "timed"表示是否对其进行定量的耗时分析。
mysql> SELECT * FROM setup_instruments limit 10;
+-------------------------------------------------------+---------+-------+
| NAME | ENABLED | TIMED |
+-------------------------------------------------------+---------+-------+
| wait/synch/mutex/sql/PAGE::lock | YES | YES |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_sync | YES | YES |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_active | YES | YES |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_pool | YES | YES |
| wait/synch/mutex/sql/LOCK_des_key_file | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_commit | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_commit_queue | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_done | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_flush_queue | YES | YES |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_index | YES | YES |
+-------------------------------------------------------+---------+-------+
10 rows in set (0.01 sec)
2）setup_objects
setup_objects类似某类病人(精神病，男科，妇科等)，在MySQL中指table, 表示哪些表需要“instrument”,该表的默认值为：
mysql> SELECT * FROM setup_objects limit 10;
+-------------+--------------------+-------------+---------+-------+
| OBJECT_TYPE | OBJECT_SCHEMA | OBJECT_NAME | ENABLED | TIMED |
+-------------+--------------------+-------------+---------+-------+
| TABLE | mysql | % | NO | NO |
| TABLE | performance_schema | % | NO | NO |
| TABLE | information_schema | % | NO | NO |
| TABLE | % | % | YES | YES |
+-------------+--------------------+-------------+---------+-------+
4 rows in set (0.00 sec)
表示出了系统表“mysql performance_schema information_schema”外，都需要对其进行“instrument”操作。
3）threads
"threads“类似于某个病人，在MySQL中的某个线程，这个表有一个非常重要的字段”INSTRUMENTED“，表示是否需要对该线程进行”instrument“,这个字段由”setup_actors“表中的内容决定。setup_actors的默认内容如下
mysql> SELECT THREAD_ID,NAME,TYPE,INSTRUMENTED,role FROM threads limit 10;
+-----------+---------------------------------+------------+--------------+------+
| THREAD_ID | NAME | TYPE | INSTRUMENTED | role |
+-----------+---------------------------------+------------+--------------+------+
| 1 | thread/sql/main | BACKGROUND | YES | NULL |
| 2 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
| 3 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
| 4 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
| 5 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
| 6 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
| 7 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
| 8 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
| 11 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
| 9 | thread/innodb/io_handler_thread | BACKGROUND | YES | NULL |
+-----------+---------------------------------+------------+--------------+------+
10 rows in set (0.01 sec)
线程分前台线程和后台线程，后台线程指MySQL为了完成任务二自己开启的线程，这样的线程的setup_objects.INSTRUMENTED字段默认为true。
前台线程值用户操作而开启的线程。这时如果当前用户匹配setup_actors中的某个记录，那么setup_objects.INSTRUMENTED=true.
threads表的另一个功能是可以代替"show processlist"指令和"information_schema.processlist"表的功能，其不用获取同步的mutex对象，不会又那么重的额外消耗(overhead).
4)setup_consumers
setup_consumers表类似于各种诊断报告是否需要记录的配置，这个表的默认配置为：select * from setup_consumers;
mysql> select * from setup_consumers;
+--------------------------------+---------+
| NAME | ENABLED |
+--------------------------------+---------+
| events_stages_current | YES |
| events_stages_history | YES |
| events_stages_history_long | YES |
| events_statements_current | YES |
| events_statements_history | YES |
| events_statements_history_long | YES |
| events_waits_current | YES |
| events_waits_history | YES |
| events_waits_history_long | YES |
| global_instrumentation | YES |
| thread_instrumentation | YES |
| statements_digest | YES |
+--------------------------------+---------+
12 rows in set (0.00 sec)
5）setup_actors
mysql> select * from setup_actors ;
+------+------+------+
| HOST | USER | ROLE |
+------+------+------+
| % | % | % |
+------+------+------+
1 row in set (0.16 sec)
6) setup_timers
mysql> select * from setup_timers ;
+-----------+-------------+
| NAME | TIMER_NAME |
+-----------+-------------+
| idle | MICROSECOND |
| wait | CYCLE |
| stage | NANOSECOND |
| statement | NANOSECOND |
+-----------+-------------+
4 rows in set (0.00 sec)
这个表的各个记录还存在层级关系，只有当上级的配置启用时才会考虑下级的配置。
层级关系为：
global_instrumentation
|----thread_instrumentation
| |----events_waits_current
| | |-events_waits_history
| | |-events_waits_history_long
| |----events_stages_current
| | |-events_stages_history
| | |-events_stages_history_long
| |----events_statements_current
| |-events_statements_history
| |-events_statements_history_long
|-----statements_digest
当global_instrumentation启用时，"thread_instrumentation"和"statements_digest"的配置才有可能生效。其他的配置类推。
只有当"setup_instruments"，"setup_objects",”setup_consumers“和"threads"都某一项测量指标都启用时才能收集到它的信息。