MySql启动报错,无法更新PID文件

MySql启动报错
Starting MySQL.. ERROR! The server quit without updating PID file (/var/lib/mysql..）

1，查看错误日志

2017-08-10 19:38:14 31865 [Note] InnoDB: Initializing buffer pool, size = 50.0M
InnoDB: mmap(53657600 bytes) failed; errno 12
2017-08-10 19:38:14 31865 [ERROR] InnoDB: Cannot allocate memory for the buffer pool
2017-08-10 19:38:14 31865 [ERROR] Plugin 'InnoDB' init function returned error.
2017-08-10 19:38:14 31865 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2017-08-10 19:38:14 31865 [ERROR] Unknown/unsupported storage engine: InnoDB
2017-08-10 19:38:14 31865 [ERROR] Aborting

2，查看空间使用量
free -ml

total used free shared buffers cached
Mem: 608476 565044 43432 0 1284 53996
-/+ buffers/cache: 509764 98712
Swap: 0 0 0

发现Swap 无可用空间(由于本人用的京东云最低配1C1G1M)

3，增加Swap空间

dd if=/dev/zero of=/home/swap bs=1024 count=512000

/sbin/mkswap /home/swap

再接着使用这个swap分区。使其成为有效状态。
/sbin/swapon /home/swap

4,重启Mysql

service mysql restart

ps:my.cnf