记一次 mysql 启动没反应 ，重启linux又可以启动

vim /var/log/mysqld.log

2018-02-04 13:22:49 28507 [ERROR] InnoDB: Cannot allocate memory for the buffer pool
2018-02-04 13:22:49 28507 [ERROR] Plugin 'InnoDB' init function returned error.
2018-02-04 13:22:49 28507 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2018-02-04 13:22:49 28507 [ERROR] Unknown/unsupported storage engine: InnoDB
2018-02-04 13:22:49 28507 [ERROR] Aborting

​​https://stackoverflow.com/questions/25965638/mysql-fatal-error-cannot-allocate-memory-for-the-buffer-pool​​

最终找到了解决方法​

于是继续，来看看内存占用情况：

 



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  1. <span style="font-size:18px;">[root@iZuzc9f4ma6h2iZ ~]# free -m
  2. total        used        free      shared  buff/cache   available
  3. Mem:            992         435         413           1         142         403
  4. Swap:             0           0           0</span>


 

显然，结果很磕馋。内存仅413M，而且没有 Swap 分区。

那么问题来了，mysql 启动到底需要多少内存？

官网是这什么回答的：

 

​​How MySQL Uses Memory​​？

MySQL allocates buffers and caches to improve performance of database operations. The default configuration is designed to permit a MySQL server to start on a virtual machine that has approximately512MB of RAM. You can improve MySQL performance by increasing the values of certain cache and buffer-related system variables. You can also modify the default configuration to run MySQL on systems with limited memory.

于是，那么有什么办法可以小内存启动 mysql 吗？

答案是有，

vim /etc/my.cnf

添加：

performance_schema_max_table_instances=200 table_definition_cache=200 table_open_cache=128

ok，再次运行 service mysqld restart ，没什么问题。