配置云主机虚拟内存：
dd if=/dev/zero of=/mnt/swap bs=block_size count=number_of_block
dd if=/dev/zero of=/mnt/swap bs=1M count=8192
mkswap /mnt/swap
swapon /mnt/swap
vi /etc/fstab
/mnt/swap swap swap defaults 0 0
vi /etc/sysctl.conf
vm.swappiness=60
sysctl -p
swapon -a 开启
swapoff -a 关闭