How to enable swap space on xen VPS?

■ Requirement : Enable swap space on xen VPS
■ OS Environment : Linux[RHEL, Centos]
■ Application:mkswap
■ Implementation Steps : 

$ dd if=/dev/zero of=/swap bs=1024 count=1048576
$ mkswap /swap
$ chmod 0600 /swap

Edit /etc/fstab & put following entry :

/swap swap swap defaults,noatime 0 0

$swapon -a
$ free -m