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米ySQL 5.7 Reference Manual
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14.17.2 Monitoring InnoDB Mutex Waits Using Performance Schema

A mutex is a synchronization mechanism used in the code to enforce that only one thread at a given time can have access to a common resource. When two or more threads executing in the server need to access the same resource, the threads compete against each other. The first thread to obtain a lock on the mutex causes the other threads to wait until the lock is released.

ForInnoDBmutexes that are instrumented, mutex waits can be monitored usingPerformance Schema. Wait event data collected in Performance Schema tables can help identify mutexes with the most waits or the greatest total wait time, for example.

The following example demonstrates how to enableInnoDBmutex wait instruments, how to enable associated consumers, and how to query wait event data.

  1. To view availableInnoDBmutex wait instruments, query the Performance Schemasetup_instrumentstable, as shown below. AllInnoDBmutex wait instruments are disabled by default.

    mysql> SELECT * FROM performance_schema.setup_instruments WHERE NAME LIKE '%wait/synch/mutex/innodb%'; +-------------------------------------------------------+---------+-------+ | NAME | ENABLED | TIMED | +-------------------------------------------------------+---------+-------+ | wait/synch/mutex/innodb/commit_cond_mutex | NO | NO | | wait/synch/mutex/innodb/innobase_share_mutex | NO | NO | | wait/synch/mutex/innodb/autoinc_mutex | NO | NO | | wait/synch/mutex/innodb/buf_pool_mutex | NO | NO | | wait/synch/mutex/innodb/buf_pool_zip_mutex | NO | NO | | wait/synch/mutex/innodb/cache_last_read_mutex | NO | NO | | wait/synch/mutex/innodb/dict_foreign_err_mutex | NO | NO | | wait/synch/mutex/innodb/dict_sys_mutex | NO | NO | | wait/synch/mutex/innodb/recalc_pool_mutex | NO | NO | | wait/synch/mutex/innodb/file_format_max_mutex | NO | NO | | wait/synch/mutex/innodb/fil_system_mutex | NO | NO | | wait/synch/mutex/innodb/flush_list_mutex | NO | NO | | wait/synch/mutex/innodb/fts_bg_threads_mutex | NO | NO | | wait/synch/mutex/innodb/fts_delete_mutex | NO | NO | | wait/synch/mutex/innodb/fts_optimize_mutex | NO | NO | | wait/synch/mutex/innodb/fts_doc_id_mutex | NO | NO | | wait/synch/mutex/innodb/log_flush_order_mutex | NO | NO | | wait/synch/mutex/innodb/hash_table_mutex | NO | NO | | wait/synch/mutex/innodb/ibuf_bitmap_mutex | NO | NO | | wait/synch/mutex/innodb/ibuf_mutex | NO | NO | | wait/synch/mutex/innodb/ibuf_pessimistic_insert_mutex | NO | NO | | wait/synch/mutex/innodb/log_sys_mutex | NO | NO | | wait/synch/mutex/innodb/page_zip_stat_per_index_mutex | NO | NO | | wait/synch/mutex/innodb/purge_sys_pq_mutex | NO | NO | | wait/synch/mutex/innodb/recv_sys_mutex | NO | NO | | wait/synch/mutex/innodb/recv_writer_mutex | NO | NO | | wait/synch/mutex/innodb/redo_rseg_mutex | NO | NO | | wait/synch/mutex/innodb/noredo_rseg_mutex | NO | NO | | wait/synch/mutex/innodb/rw_lock_list_mutex | NO | NO | | wait/synch/mutex/innodb/rw_lock_mutex | NO | NO | | wait/synch/mutex/innodb/srv_dict_tmpfile_mutex | NO | NO | | wait/synch/mutex/innodb/srv_innodb_monitor_mutex | NO | NO | | wait/synch/mutex/innodb/srv_misc_tmpfile_mutex | NO | NO | | wait/synch/mutex/innodb/srv_monitor_file_mutex | NO | NO | | wait/synch/mutex/innodb/buf_dblwr_mutex | NO | NO | | wait/synch/mutex/innodb/trx_undo_mutex | NO | NO | | wait/synch/mutex/innodb/trx_pool_mutex | NO | NO | | wait/synch/mutex/innodb/trx_pool_manager_mutex | NO | NO | | wait/synch/mutex/innodb/srv_sys_mutex | NO | NO | | wait/synch/mutex/innodb/lock_mutex | NO | NO | | wait/synch/mutex/innodb/lock_wait_mutex | NO | NO | | wait/synch/mutex/innodb/trx_mutex | NO | NO | | wait/synch/mutex/innodb/srv_threads_mutex | NO | NO | | wait/synch/mutex/innodb/rtr_active_mutex | NO | NO | | wait/synch/mutex/innodb/rtr_match_mutex | NO | NO | | wait/synch/mutex/innodb/rtr_path_mutex | NO | NO | | wait/synch/mutex/innodb/rtr_ssn_mutex | NO | NO | | wait/synch/mutex/innodb/trx_sys_mutex | NO | NO | | wait/synch/mutex/innodb/zip_pad_mutex | NO | NO | +-------------------------------------------------------+---------+-------+ 49 rows in set (0.02 sec)
  2. SomeInnoDBmutex instances are created at server startup and are only instrumented if the associated instrument is also enabled at server startup. To ensure that allInnoDBmutex instances are instrumented and enabled, add the followingperformance-schema-instrumentrule to your MySQL configuration file:

    performance-schema-instrument='wait/synch/mutex/innodb/%=ON'

    If you do not require wait event data for allInnoDB互斥锁,您可以禁用特定的工具dding additionalperformance-schema-instrumentrules to your MySQL configuration file. For example, to disableInnoDBmutex wait event instruments related to full-text search, add the following rule:

    performance-schema-instrument='wait/synch/mutex/innodb/fts%=OFF'
    Note

    Rules with a longer prefix such aswait/synch/mutex/innodb/fts%take precedence over rules with shorter prefixes such aswait/synch/mutex/innodb/%.

    After adding theperformance-schema-instrumentrules to your configuration file, restart the server. All theInnoDBmutexes except for those related to full text search are enabled. To verify, query thesetup_instrumentstable. TheENABLEDandTIMEDcolumns should be set toYESfor the instruments that you enabled.

    mysql> SELECT * FROM performance_schema.setup_instruments WHERE NAME LIKE '%wait/synch/mutex/innodb%'; +-------------------------------------------------------+---------+-------+ | NAME | ENABLED | TIMED | +-------------------------------------------------------+---------+-------+ | wait/synch/mutex/innodb/commit_cond_mutex | YES | YES | | wait/synch/mutex/innodb/innobase_share_mutex | YES | YES | | wait/synch/mutex/innodb/autoinc_mutex | YES | YES | ... | wait/synch/mutex/innodb/zip_pad_mutex | YES | YES | +-------------------------------------------------------+---------+-------+ 49 rows in set (0.00 sec)
  3. Enable wait event consumers by updating thesetup_consumerstable. Wait event consumers are disabled by default.

    mysql> UPDATE performance_schema.setup_consumers SET enabled = 'YES' WHERE name like 'events_waits%'; Query OK, 3 rows affected (0.00 sec) Rows matched: 3 Changed: 3 Warnings: 0

    You can verify that wait event consumers are enabled by querying thesetup_consumerstable. Theevents_waits_current,events_waits_history, andevents_waits_history_longconsumers should be 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_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 | YES | | events_waits_history | YES | | events_waits_history_long | YES | | global_instrumentation | YES | | thread_instrumentation | YES | | statements_digest | YES | +----------------------------------+---------+ 15 rows in set (0.00 sec)
  4. Once instruments and consumers are enabled, run the workload that you want to monitor. In this example, themysqlslapload emulation client is used to simulate a workload.

    $> ./mysqlslap --auto-generate-sql --concurrency=100 --iterations=10 --number-of-queries=1000 --number-char-cols=6 --number-int-cols=6;
  5. Query the wait event data. In this example, wait event data is queried from theevents_waits_summary_global_by_event_nametable which aggregates data found in theevents_waits_current,events_waits_history, andevents_waits_history_longtables. Data is summarized by event name (EVENT_NAME), which is the name of the instrument that produced the event. Summarized data includes:

    • COUNT_STAR

      The number of summarized wait events.

    • SUM_TIMER_WAIT

      The total wait time of the summarized timed wait events.

    • 米IN_TIMER_WAIT

      The minimum wait time of the summarized timed wait events.

    • AVG_TIMER_WAIT

      The average wait time of the summarized timed wait events.

    • 米AX_TIMER_WAIT

      的最大等待时间总结时间等events.

    The following query returns the instrument name (EVENT_NAME), the number of wait events (COUNT_STAR), and the total wait time for the events for that instrument (SUM_TIMER_WAIT)。Because waits are timed in picoseconds (trillionths of a second) by default, wait times are divided by 1000000000 to show wait times in milliseconds. Data is presented in descending order, by the number of summarized wait events (COUNT_STAR)。你可以调整ORDER BYclause to order the data by total wait time.

    mysql> SELECT EVENT_NAME, COUNT_STAR, SUM_TIMER_WAIT/1000000000 SUM_TIMER_WAIT_MS FROM performance_schema.events_waits_summary_global_by_event_name WHERE SUM_TIMER_WAIT > 0 AND EVENT_NAME LIKE 'wait/synch/mutex/innodb/%' ORDER BY COUNT_STAR DESC; +--------------------------------------------------+------------+-------------------+ | EVENT_NAME | COUNT_STAR | SUM_TIMER_WAIT_MS | +--------------------------------------------------+------------+-------------------+ | wait/synch/mutex/innodb/os_mutex | 78831 | 10.3283 | | wait/synch/mutex/innodb/log_sys_mutex | 41488 | 6510.3233 | | wait/synch/mutex/innodb/trx_sys_mutex | 29770 | 1107.9687 | | wait/synch/mutex/innodb/lock_mutex | 24212 | 104.0724 | | wait/synch/mutex/innodb/trx_mutex | 22756 | 1.9421 | | wait/synch/mutex/innodb/rseg_mutex | 20333 | 3.6220 | | wait/synch/mutex/innodb/dict_sys_mutex | 13422 | 2.2284 | | wait/synch/mutex/innodb/mutex_list_mutex | 12694 | 344.1164 | | wait/synch/mutex/innodb/fil_system_mutex | 9208 | 0.9542 | | wait/synch/mutex/innodb/rw_lock_list_mutex | 8304 | 0.1794 | | wait/synch/mutex/innodb/trx_undo_mutex | 6190 | 0.6801 | | wait/synch/mutex/innodb/buf_pool_mutex | 2869 | 29.4623 | | wait/synch/mutex/innodb/innobase_share_mutex | 2005 | 0.1349 | | wait/synch/mutex/innodb/flush_list_mutex | 1274 | 0.1300 | | wait/synch/mutex/innodb/file_format_max_mutex | 1016 | 0.0469 | | wait/synch/mutex/innodb/purge_sys_bh_mutex | 1004 | 0.0326 | | wait/synch/mutex/innodb/buf_dblwr_mutex | 640 | 0.0437 | | wait/synch/mutex/innodb/log_flush_order_mutex | 437 | 0.0510 | | wait/synch/mutex/innodb/recv_sys_mutex | 394 | 0.0202 | | wait/synch/mutex/innodb/srv_sys_mutex | 169 | 0.5259 | | wait/synch/mutex/innodb/lock_wait_mutex | 154 | 0.1172 | | wait/synch/mutex/innodb/ibuf_mutex | 9 | 0.0027 | | wait/synch/mutex/innodb/srv_innodb_monitor_mutex | 2 | 0.0009 | | wait/synch/mutex/innodb/ut_list_mutex | 1 | 0.0001 | | wait/synch/mutex/innodb/recv_writer_mutex | 1 | 0.0005 | +--------------------------------------------------+------------+-------------------+ 25 rows in set (0.01 sec)
    Note

    The preceding result set includes wait event data produced during the startup process. To exclude this data, you can truncate theevents_waits_summary_global_by_event_nametable immediately after startup and before running your workload. However, the truncate operation itself may produce a negligible amount wait event data.

    mysql> TRUNCATE performance_schema.events_waits_summary_global_by_event_name;