为什么我的c程序突然使用了30g的虚拟内存?

In top, I noticed that my c program (using CUDA 3.2) has a virtual size of 28g or more (looking at VIRT), on every run right from the beginning. This doesn't make ANY sense to me. The resident memory makes sense and is only around 2g on my largest data set. I know at some point in the past the virtual size was not so large, but I'm not sure when the change occurred.In top, I noticed that my c program (using CUDA