Performance Schema memory_global_by_event_name Table
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MariaDB starting with 10.5.2
The memory_summary_global_by_event_name table was introduced in MariaDB 10.5.2.
There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:
- memory_summary_by_account_by_event_name
- memory_summary_by_host_by_event_name
- memory_summary_by_thread_by_event_name
- memory_summary_by_user_by_event_name
- memory_global_by_event_name
The memory_summary_global_by_event_name table contains memory usage statistics aggregated by event and event.
The table contains the following columns:
| Field | Type | Null | Default | Description |
|---|---|---|---|---|
| EVENT_NAME | varchar(128) | NO | NULL | Event name. |
| COUNT_ALLOC | bigint(20) unsigned | NO | NULL | Total number of allocations to memory. |
| COUNT_FREE | bigint(20) unsigned | NO | NULL | Total number of attempts to free the allocated memory. |
| SUM_NUMBER_OF_BYTES_ALLOC | bigint(20) unsigned | NO | NULL | Total number of bytes allocated. |
| SUM_NUMBER_OF_BYTES_FREE | bigint(20) unsigned | NO | NULL | Total number of bytes freed |
| LOW_COUNT_USED | bigint(20) | NO | NULL | Lowest number of allocated blocks (lowest value of CURRENT_COUNT_USED). |
| CURRENT_COUNT_USED | bigint(20) | NO | NULL | Currently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE). |
| HIGH_COUNT_USED | bigint(20) | NO | NULL | Highest number of allocated blocks (highest value of CURRENT_COUNT_USED). |
| LOW_NUMBER_OF_BYTES_USED | bigint(20) | NO | NULL | Lowest number of bytes used. |
| CURRENT_NUMBER_OF_BYTES_USED | bigint(20) | NO | NULL | Current number of bytes used (total allocated minus total freed). |
| HIGH_NUMBER_OF_BYTES_USED | bigint(20) | NO | NULL | Highest number of bytes used. |
Example
Seeing what memory was most often allocated for:
SELECT * FROM memory_summary_global_by_event_name
ORDER BY count_alloc DESC LIMIT 1\G
*************************** 1. row ***************************
EVENT_NAME: memory/sql/QUICK_RANGE_SELECT::alloc
COUNT_ALLOC: 147976
COUNT_FREE: 147976
SUM_NUMBER_OF_BYTES_ALLOC: 600190656
SUM_NUMBER_OF_BYTES_FREE: 600190656
LOW_COUNT_USED: 0
CURRENT_COUNT_USED: 0
HIGH_COUNT_USED: 68
LOW_NUMBER_OF_BYTES_USED: 0
CURRENT_NUMBER_OF_BYTES_USED: 0
HIGH_NUMBER_OF_BYTES_USED: 275808
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