1 个用户可以正常工作，但人数大于 5， mysql 数据库就自动关闭了，求帮助！

以下是错误日志，请问是什么原因导致数据库自动关闭，谢谢。

160305 1:31:42 [Warning] IP address '121.42.0.16' could not be resolved: Name or service not known
160305 1:31:42 [Warning] IP address '121.42.0.16' could not be resolved: Name or service not known
160305 1:44:36 [Warning] IP address '114.215.185.137' could not be resolved: Name or service not known
160305 9:47:51 [Warning] IP address '121.196.244.10' could not be resolved: Name or service not known
Killed
160305 14:55:51 mysqld_safe Number of processes running now: 0
160305 14:55:51 mysqld_safe mysqld restarted
160305 14:55:52 [Note] Plugin 'FEDERATED' is disabled.
160305 14:55:52 InnoDB: The InnoDB memory heap is disabled
160305 14:55:52 InnoDB: Mutexes and rw_locks use GCC atomic builtins
160305 14:55:52 InnoDB: Compressed tables use zlib 1.2.3
160305 14:55:52 InnoDB: Using Linux native AIO
160305 14:55:52 InnoDB: Initializing buffer pool, size = 128.0M
InnoDB: mmap(137363456 bytes) failed; errno 12
160305 14:55:52 InnoDB: Completed initialization of buffer pool
160305 14:55:52 InnoDB: Fatal error: cannot allocate memory for the buffer pool
160305 14:55:52 [ERROR] Plugin 'InnoDB' init function returned error.
160305 14:55:52 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
160305 14:55:52 [ERROR] Unknown/unsupported storage engine: InnoDB
160305 14:55:52 [ERROR] Aborting

160305 14:55:52 [Note] /alidata/server/mysql/bin/mysqld: Shutdown complete

160305 14:55:52 mysqld_safe mysqld from pid file /alidata/server/mysql/data/iZ2892tr3o4Z.pid ended