Swap is kind of a "safety net" in case you run out of RAM, so the fact that it's not used until actually needed is entirely normal.
You're not using any swap because all the processes fit in your RAM. You won't actually see swap being used util processes actually need more space. Try opening a lot of tabs on your browser, or install the stress tool which you can use to stress your system's memory, and you will see swap being used.
官网上外国人的回答，大概意思是重新分配swap空间,希望前辈给我解决一下，不要打击我使用ubuntu的信息
