centOS7 上 mysql 服务经常无故 dead，有 log，请各路大神会诊

查看 log 初步判断为服务自动终止，原因是内存溢出，我以前的主机是 1GB 的 ram ，以为是内存太小，升级到了 2GB ，结果还是这个问题，其实我觉得和内存大小没有太大关系，因为我用过万网的虚拟主机， 512MB 的都能跑的好好的，自从迁移到 ECS 上后就问题不断。请各位大神帮忙看下这个 log ，为何内存总是溢出，感谢！

maridb log 如下：
161003 3:45:07 [Warning] IP address '121.28.142.136' could not be resolved: Name or service not known
161003 3:45:07 [Warning] IP address '121.28.142.138' could not be resolved: Name or service not known
161003 3:45:08 [Warning] IP address '121.28.142.133' could not be resolved: Name or service not known
161003 7:05:41 [Warning] IP address '69.165.72.94' could not be resolved: Name or service not known
161003 11:37:43 [Warning] IP address '123.249.3.155' could not be resolved: Name or service not known
161003 12:28:12 [Warning] IP address '121.199.70.200' could not be resolved: Name or service not known
161004 0:10:16 [Warning] IP address '139.224.53.6' could not be resolved: Name or service not known
161004 0:19:28 [Warning] IP address '124.173.113.45' could not be resolved: Name or service not known
161004 00:38:31 mysqld_safe Number of processes running now: 0
161004 00:38:31 mysqld_safe mysqld restarted
161004 0:38:31 [Note] /usr/libexec/mysqld (mysqld 5.5.50-MariaDB) starting as process 27071 ...
161004 0:38:31 [Warning] Changed limits: max_open_files: 1024 max_connections: 214 table_cache: 400
161004 0:38:31 InnoDB: The InnoDB memory heap is disabled
161004 0:38:31 InnoDB: Mutexes and rw_locks use GCC atomic builtins
161004 0:38:31 InnoDB: Compressed tables use zlib 1.2.7
161004 0:38:31 InnoDB: Using Linux native AIO
161004 0:38:31 InnoDB: Initializing buffer pool, size = 128.0M
InnoDB: mmap(137756672 bytes) failed; errno 12
161004 0:38:31 InnoDB: Completed initialization of buffer pool
161004 0:38:31 InnoDB: Fatal error: cannot allocate memory for the buffer pool
161004 0:38:31 [ERROR] Plugin 'InnoDB' init function returned error.
161004 0:38:31 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
161004 0:38:31 [ERROR] mysqld: Out of memory (Needed 128917504 bytes)
161004 0:38:31 [ERROR] mysqld: Out of memory (Needed 96681984 bytes)
161004 0:38:31 [ERROR] mysqld: Out of memory (Needed 72499200 bytes)
161004 0:38:33 [Note] Plugin 'FEEDBACK' is disabled.
161004 0:38:33 [ERROR] Unknown/unsupported storage engine: InnoDB
161004 0:38:33 [ERROR] Aborting

161004 0:38:33 [Note] /usr/libexec/mysqld: Shutdown complete

161004 00:38:33 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended

msg7086

2016-10-04 11:50:09 +08:00

@Famio 进程有一个「使用内存」和一个「申请内存」。
你平时看到的进程内存占用都是「使用内存」，但是触发 Kill 的却是「申请内存」。
所以你会发现明明内存还有空余，却报内存不足。
Linux 和 Windows 都是这样子的。 Windows 你可以看有个提交内存， Commit Charge ，这个就是「申请内存」。
如果 Windows 下不开分页文件，那么申请内存就等于物理内存，这种情况下内存还没用满就会提前导致系统去杀进程了。
Linux 有个内核参数可以控制 Over Commit ，有兴趣的话可以当做扩展阅读。
https://www.kernel.org/doc/Documentation/vm/overcommit-accounting