要查看可用的 MySQL 内存检测，请查询 Performance Schema setup_instruments 表。以下查询将返回所有代码区域的数百个内存检测。

mysql> SELECT * FROM performance_schema.setup_instruments
       WHERE NAME LIKE '%memory%';

您可以通过指定代码区域来缩小结果范围。例如，您可以通过将 innodb 指定为代码区域来限制结果范围，使其仅包含 InnoDB 内存检测。

mysql> SELECT * FROM performance_schema.setup_instruments
       WHERE NAME LIKE '%memory/innodb%';
+-------------------------------------------+---------+-------+
| NAME                                      | ENABLED | TIMED |
+-------------------------------------------+---------+-------+
| memory/innodb/adaptive hash index         | NO      | NO    |
| memory/innodb/buf_buf_pool                | NO      | NO    |
| memory/innodb/dict_stats_bg_recalc_pool_t | NO      | NO    |
| memory/innodb/dict_stats_index_map_t      | NO      | NO    |
| memory/innodb/dict_stats_n_diff_on_level  | NO      | NO    |
| memory/innodb/other                       | NO      | NO    |
| memory/innodb/row_log_buf                 | NO      | NO    |
| memory/innodb/row_merge_sort              | NO      | NO    |
| memory/innodb/std                         | NO      | NO    |
| memory/innodb/trx_sys_t::rw_trx_ids       | NO      | NO    |
...

根据您的 MySQL 安装情况，代码区域可能包括 performance_schema、sql、client、innodb、myisam、csv、memory、blackhole、archive、partition 等。

要启用内存检测，请在您的 MySQL 配置文件中添加 performance-schema-instrument 规则。例如，要启用所有内存检测，请将此规则添加到您的配置文件并重新启动服务器

performance-schema-instrument='memory/%=COUNTED'

重新启动服务器后，Performance Schema setup_instruments 表的 ENABLED 列应报告您启用的内存检测的 YES。在 setup_instruments 表中，TIMED 列对于内存检测来说是会被忽略的，因为内存操作不会计时。

mysql> SELECT * FROM performance_schema.setup_instruments
       WHERE NAME LIKE '%memory/innodb%';
+-------------------------------------------+---------+-------+
| NAME                                      | ENABLED | TIMED |
+-------------------------------------------+---------+-------+
| memory/innodb/adaptive hash index         | NO      | NO    |
| memory/innodb/buf_buf_pool                | NO      | NO    |
| memory/innodb/dict_stats_bg_recalc_pool_t | NO      | NO    |
| memory/innodb/dict_stats_index_map_t      | NO      | NO    |
| memory/innodb/dict_stats_n_diff_on_level  | NO      | NO    |
| memory/innodb/other                       | NO      | NO    |
| memory/innodb/row_log_buf                 | NO      | NO    |
| memory/innodb/row_merge_sort              | NO      | NO    |
| memory/innodb/std                         | NO      | NO    |
| memory/innodb/trx_sys_t::rw_trx_ids       | NO      | NO    |
...

查询内存检测数据。在此示例中，内存检测数据是在 Performance Schema memory_summary_global_by_event_name 表中查询的，该表根据 EVENT_NAME 对数据进行汇总。该 EVENT_NAME 是检测的名称。

以下查询将返回 InnoDB 缓冲池的内存数据。有关列描述的详细信息，请参阅 第 29.12.20.10 节，“内存汇总表”。

mysql> SELECT * FROM performance_schema.memory_summary_global_by_event_name
       WHERE EVENT_NAME LIKE 'memory/innodb/buf_buf_pool'\G
                  EVENT_NAME: memory/innodb/buf_buf_pool
                 COUNT_ALLOC: 1
                  COUNT_FREE: 0
   SUM_NUMBER_OF_BYTES_ALLOC: 137428992
    SUM_NUMBER_OF_BYTES_FREE: 0
              LOW_COUNT_USED: 0
          CURRENT_COUNT_USED: 1
             HIGH_COUNT_USED: 1
    LOW_NUMBER_OF_BYTES_USED: 0
CURRENT_NUMBER_OF_BYTES_USED: 137428992
   HIGH_NUMBER_OF_BYTES_USED: 137428992

相同的基础数据可以使用 sys schema memory_global_by_current_bytes 表来查询，该表显示了服务器全局范围内当前的内存使用情况，并根据分配类型进行了细分。

mysql> SELECT * FROM sys.memory_global_by_current_bytes
       WHERE event_name LIKE 'memory/innodb/buf_buf_pool'\G
*************************** 1. row ***************************
       event_name: memory/innodb/buf_buf_pool
    current_count: 1
    current_alloc: 131.06 MiB
current_avg_alloc: 131.06 MiB
       high_count: 1
       high_alloc: 131.06 MiB
   high_avg_alloc: 131.06 MiB

此 sys schema 查询按代码区域汇总当前分配的内存 (current_alloc)

mysql> SELECT SUBSTRING_INDEX(event_name,'/',2) AS
       code_area, FORMAT_BYTES(SUM(current_alloc))
       AS current_alloc
       FROM sys.x$memory_global_by_current_bytes
       GROUP BY SUBSTRING_INDEX(event_name,'/',2)
       ORDER BY SUM(current_alloc) DESC;
+---------------------------+---------------+
| code_area                 | current_alloc |
+---------------------------+---------------+
| memory/innodb             | 843.24 MiB    |
| memory/performance_schema | 81.29 MiB     |
| memory/mysys              | 8.20 MiB      |
| memory/sql                | 2.47 MiB      |
| memory/memory             | 174.01 KiB    |
| memory/myisam             | 46.53 KiB     |
| memory/blackhole          | 512 bytes     |
| memory/federated          | 512 bytes     |
| memory/csv                | 512 bytes     |
| memory/vio                | 496 bytes     |
+---------------------------+---------------+

有关 sys schema 的更多信息，请参阅 第 30 章，MySQL sys Schema。