MySQL内存分析常用语句

一、 OS层

首先需要确认是否是MySQL占用的内存

top -p $(pidof mysqld) -n 1

或者

cat /proc/$(pidof mysqld)/status

二、 DB层

全局情况

各种buffer pool大小，是否有明显不合理的设置

SHOW GLOBAL VARIABLES LIKE '%buffer%szie%';

MySQL总占用内存

SELECT * FROM sys.memory_global_total;

内存占用详情

按内存模块

SELECT

EVENT_NAME,

CURRENT_NUMBER_OF_BYTES_USED AS memory_bytes,

CURRENT_NUMBER_OF_BYTES_USED / 1024 / 1024 AS memory_mb

FROM

performance_schema.memory_summary_global_by_event_name

WHERE

CURRENT_NUMBER_OF_BYTES_USED > 0

ORDER BY

CURRENT_NUMBER_OF_BYTES_USED DESC

LIMIT 10;

各模块内存使用变化（结果是累计值，可以根据差值观察变化情况）

多次查询，求差值

SELECT

EVENT_NAME,

SUM(SUM_NUMBER_OF_BYTES_ALLOC) / 1024 / 1024 AS total_memory_mb

FROM

performance_schema.memory_summary_global_by_event_name

GROUP BY

EVENT_NAME

ORDER BY

SUM_NUMBER_OF_BYTES_ALLOC DESC

LIMIT 10;

按线程查看内存占用

SELECT

m.EVENT_NAME,

m.COUNT_ALLOC,

m.CURRENT_NUMBER_OF_BYTES_USED AS mem_sum,

(m.CURRENT_NUMBER_OF_BYTES_USED / 1024 / 1024.0) AS mem_sum_mb,

t.NAME,

t.TYPE,

t.PROCESSLIST_ID,

LEFT(t.PROCESSLIST_INFO, 10)

FROM

performance_schema.memory_summary_by_thread_by_event_name m

JOIN performance_schema.threads t

USING (THREAD_ID)

WHERE

t.PROCESSLIST_ID != CONNECTION_ID()

ORDER BY

m.CURRENT_NUMBER_OF_BYTES_USED desc

LIMIT 10;

sys库中的视图基于 performance_schema 提供了更易读和易用的性能数据汇总

SELECT * FROM sys.memory_by_thread_by_current_bytes LIMIT 10;

内存分布详情

SELECT * FROM sys.memory_global_by_current_bytes order by current_alloc desc LIMIT 10;

按用户排序

SELECT * FROM sys.memory_by_user_by_current_bytes;

参考

GreatSQL 运行时内存太高，超过90%怎么办（重发，附解决办法）-CSDN博客

MySQL内存使用率高且不释放问题排查与总结_Mysql_脚本之家

MySQL 8.0不再担心被垃圾SQL搞爆内存 - GreatSQL - 博客园

MySQL内存为什么不断增高，怎么让它释放 - 墨天轮

MySQL进程内存一直在涨，怎么办？ - 墨天轮