这里有一个建议如何设置大空间的swap。可以参考redhat的做法：

Systems with 4GB of ram or less require a minimum of 2GB of swap space
Systems with 4GB to 16GB of ram require a minimum of 4GB of swap space
Systems with 16GB to 64GB of ram require a minimum of 8GB of swap space
Systems with 64GB to 256GB of ram require a minimum of 16GB of swap space