在performance_schema有如下表記錄內存使用情況
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mysql> show tables
like
'%memory%summary%'
;
+
-------------------------------------------------+
| Tables_in_performance_schema (%memory%summary%) |
+
-------------------------------------------------+
| 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_summary_global_by_event_name |
+
-------------------------------------------------+
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每個內存統計表都有如下統計列：
* COUNT_ALLOC，COUNT_FREE：對內存分配和釋放內存函數的調用總次數
* SUM_NUMBER_OF_BYTES_ALLOC，SUM_NUMBER_OF_BYTES_FREE：已分配和已釋放的內存塊的總字節大小
* CURRENT_COUNT_USED：這是一個便捷列，等於COUNT_ALLOC - COUNT_FREE
* CURRENT_NUMBER_OF_BYTES_USED：當前已分配的內存塊但未釋放的統計大小。這是一個便捷列，等於SUM_NUMBER_OF_BYTES_ALLOC - SUM_NUMBER_OF_BYTES_FREE
* LOW_COUNT_USED，HIGH_COUNT_USED：對應CURRENT_COUNT_USED列的低和高水位標記
* LOW_NUMBER_OF_BYTES_USED，HIGH_NUMBER_OF_BYTES_USED：對應CURRENT_NUMBER_OF_BYTES_USED列的低和高水位標記
內存統計表允許使用TRUNCATE TABLE語句。使用truncate語句時有如下行為：
* 通常，truncate操作會重置統計信息的基准數據（即清空之前的數據），但不會修改當前server的內存分配等狀態。也就是說，truncate內存統計表不會釋放已分配內存
* 將COUNT_ALLOC和COUNT_FREE列重置，並重新開始計數（等於內存統計信息以重置后的數值作為基准數據）
* SUM_NUMBER_OF_BYTES_ALLOC和SUM_NUMBER_OF_BYTES_FREE列重置與COUNT_ALLOC和COUNT_FREE列重置類似
* LOW_COUNT_USED和HIGH_COUNT_USED將重置為CURRENT_COUNT_USED列值
* LOW_NUMBER_OF_BYTES_USED和HIGH_NUMBER_OF_BYTES_USED將重置為CURRENT_NUMBER_OF_BYTES_USED列值
* 此外，按照帳戶，主機，用戶或線程分類統計的內存統計表或memory_summary_global_by_event_name表，如果在對其依賴的accounts、hosts、users表執行truncate時，會隱式對這些內存統計表執行truncate語句
簡單來說，就是可以根據用戶、主機、線程、賬號、全局的維度對內存進行監控。同時庫sys也就這些表做了進一步的格式化，可以使得用戶非常容易的觀察到每個對象的內存開銷：
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mysql>
select
event_name,current_alloc
from
sys.memory_global_by_current_bytes limit 10;
+
-----------------------------------------------------------------------------+---------------+
| event_name | current_alloc |
+
-----------------------------------------------------------------------------+---------------+
| memory/performance_schema/events_statements_history_long | 13.66 MiB |
| memory/performance_schema/events_statements_history_long.sqltext | 9.77 MiB |
| memory/performance_schema/events_statements_history_long.tokens | 9.77 MiB |
| memory/performance_schema/events_statements_summary_by_digest.tokens | 9.77 MiB |
| memory/performance_schema/table_handles | 9.06 MiB |
| memory/performance_schema/events_statements_summary_by_thread_by_event_name | 8.67 MiB |
| memory/sql/String::value | 6.02 MiB |
| memory/performance_schema/memory_summary_by_thread_by_event_name | 5.62 MiB |
| memory/performance_schema/events_statements_summary_by_digest | 4.88 MiB |
| memory/sql/
TABLE
| 4.35 MiB |
+
-----------------------------------------------------------------------------+---------------+
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默認情況下performance_schema只對performance_schema進行了內存開銷的統計。根據你的MySQL安裝代碼區域可能包括performance_schema、sql、client、innodb、myisam、csv、memory、blackhole、archive、partition和其他。
查看innodb相關的內存監控是否開啟，默認不開啟
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mysql>
SELECT
*
FROM
performance_schema.setup_instruments
->
WHERE
NAME
LIKE
'%memory%'
;
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+
--------------------------------------------------------------------------------+---------+-------+
|
NAME
| ENABLED | TIMED |
+
--------------------------------------------------------------------------------+---------+-------+
| memory/performance_schema/mutex_instances | YES |
NO
|
| memory/performance_schema/rwlock_instances | YES |
NO
|
| memory/performance_schema/cond_instances | YES |
NO
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| memory/performance_schema/file_instances | YES |
NO
|
| memory/performance_schema/socket_instances | YES |
NO
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| memory/performance_schema/metadata_locks | YES |
NO
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| memory/performance_schema/file_handle | YES |
NO
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| memory/performance_schema/accounts | YES |
NO
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| memory/performance_schema/events_waits_summary_by_account_by_event_name | YES |
NO
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| memory/performance_schema/events_stages_summary_by_account_by_event_name | YES |
NO
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| memory/performance_schema/events_statements_summary_by_account_by_event_name | YES |
NO
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| memory/performance_schema/events_transactions_summary_by_account_by_event_name | YES |
NO
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| memory/performance_schema/memory_summary_by_account_by_event_name | YES |
NO
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| memory/performance_schema/events_stages_summary_global_by_event_name | YES |
NO
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| memory/performance_schema/events_statements_summary_global_by_event_name | YES |
NO
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| memory/performance_schema/memory_summary_global_by_event_name | YES |
NO
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| memory/performance_schema/hosts | YES |
NO
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| memory/performance_schema/events_waits_summary_by_host_by_event_name | YES |
NO
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| memory/performance_schema/events_stages_summary_by_host_by_event_name | YES |
NO
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| memory/performance_schema/events_statements_summary_by_host_by_event_name | YES |
NO
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| memory/performance_schema/events_transactions_summary_by_host_by_event_name | YES |
NO
|
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可以通過條件縮小范圍：
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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
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| memory/innodb/dict_stats_bg_recalc_pool_t |
NO
|
NO
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| memory/innodb/dict_stats_index_map_t |
NO
|
NO
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| memory/innodb/dict_stats_n_diff_on_level |
NO
|
NO
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| memory/innodb/other |
NO
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NO
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| memory/innodb/row_log_buf |
NO
|
NO
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| memory/innodb/row_merge_sort |
NO
|
NO
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| memory/innodb/std |
NO
|
NO
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| memory/innodb/trx_sys_t::rw_trx_ids |
NO
|
NO
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對所有可能的對象進行內存監控。因此，還需要做下面的設置：
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mysql>
update
performance_schema.setup_instruments
set
enabled =
'yes'
where
name
like
'memory%'
;
Query OK, 306
rows
affected (0.00 sec)
Rows
matched: 376 Changed: 306 Warnings: 0
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但是這種在線打開內存統計的方法僅對之后新增的內存對象有效，重啟數據庫后又會還原設置：
如想要對全局生命周期中的對象進行內存統計，必須在配置文件中進行設置，然后重啟：
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[mysqld]
performance-
schema
-instrument=
'memory/%=COUNTED'
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可以使用sys庫下的memory_global_by_current_bytes表來查詢相同的底層數據，該模式表顯示了全局服務器內當前內存使用情況，按分配類型進行細分。
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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
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此sys模式查詢通過current_alloc()代碼區域聚合當前分配的內存：
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mysql>
SELECT
SUBSTRING_INDEX(event_name,
'/'
,2)
AS
code_area, sys.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 |
+
---------------------------+---------------+
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總結
以上就是這篇文章的全部內容了，希望本文的內容對大家的學習或者工作具有一定的參考學習價值，如果有疑問大家可以留言交流，謝謝大家對腳本之家的支持。