The old rule: Swap size should be twice of the RAM is only applicable in the old system when RAM is small (<1GB)
The new rule:
Swap = Equal RAM size (if RAM < 2GB)
Swap = 2GB size (if 2GB < RAM < 8GB)
Swap = 0.5 RAM size (if RAM > 8GB)
There is no benefit to put the swap size twice as RAM > 2GB since a system using up to mutiple GBs in swap memory should not be a good design for performance.