查询内存仪器数据。在这个例子中，在Performance Schema
memory_summary_global_by_event_name
表中查询内存仪器数据，该表将数据汇总为
EVENT_NAME. 这
EVENT_NAME是仪器的名称。
以下查询返回
InnoDB缓冲池的内存数据。有关列说明，请参阅
第 27.12.20.10 节，“内存摘要表”。
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
可以使用
sys架构
memory_global_by_current_bytes
表查询相同的底层数据，该表显示了服务器中全局的当前内存使用情况，按分配类型细分。
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
此模式查询按代码区域
sys聚合当前分配的内存 ( )：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 |
+---------------------------+---------------+
笔记
在 MySQL 8.0.16 之前，
sys.format_bytes()用于
FORMAT_BYTES().
有关
sys模式的更多信息，请参阅
第 28 章，MySQL 系统模式。