Amazon EC2，mysql 中止启动，因为 InnoDB：mmap(x 字节)失败；错误号 12

我有一个基于EC2的micro实例服务器

mysql服务器经常出现故障，这是mysql服务器第三次消失.日志(log)只显示

120423 09:13:38 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
120423 09:14:27 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
120423  9:14:27 [Note] Plugin 'FEDERATED' is disabled.
120423  9:14:27 InnoDB: The InnoDB memory heap is disabled
120423  9:14:27 InnoDB: Mutexes and rw_locks use GCC atomic builtins
120423  9:14:27 InnoDB: Compressed tables use zlib 1.2.3
120423  9:14:27 InnoDB: Using Linux native AIO
120423  9:14:27 InnoDB: Initializing buffer pool, size = 512.0M
InnoDB: mmap(549453824 bytes) failed; errno 12
120423  9:14:27 InnoDB: Completed initialization of buffer pool
120423  9:14:27 InnoDB: Fatal error: cannot allocate memory for the buffer pool
120423  9:14:27 [ERROR] Plugin 'InnoDB' init function returned error.
120423  9:14:27 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
120423  9:14:27 [ERROR] Unknown/unsupported storage engine: InnoDB
120423  9:14:27 [ERROR] Aborting

什么是真正的failed; errno 12？我怎样才能给它更多的空间/内存，或者任何需要的东西来修复它.

每次我都会通过重新启动整个系统、删除所有日志(log)并重新启动mysql服务器来解决这个问题.但我知道我的配置有问题.

也是我的.cnf’如下所示:

[mysqld]
# Settings user and group are ignored when systemd is used.
# If you need to run mysqld under different user or group,
# customize your systemd unit file for mysqld according to the
# instructions in http://fedoraproject.org/wiki/Systemd
# max_allowed_packet=500M
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0


innodb_buffer_pool_size         = 512M


[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid