Add zram:

    #!/bin/sh
     modprobe zram
     if [ -e /dev/zram0 ]
      then
      echo "zram0 on"
      exit 1 
      fi
      zramctl --find --size 512M 
      mkswap /dev/zram0
      swapon -p 99 /dev/zram0

Run the script as root.