cuda::GpuMat using too much memory

I'm using `cudafeatures2d` to do ORB feature matching. I want to upload all of the descriptor sets that I want to match against, but I'm finding that for some reason each `GpuMat` takes up 16x as much GPU memory as it should. For example, if I upload a descriptor Mat of 20107x32 bytes (should be 628.3 KiB), I can see in `nvidia-smi` that my process's memory usage increases by 10 **MiB**. This goes on until my total process GPU memory use reaches about 2 GiB, when it crashes with the following exception: ``` opencv-3.1.0/modules/core/src/cuda/gpu_mat.cu:71: error: (-217) out of memory in function allocate ``` This is also weird because my GPU has 6 GB of RAM, not 2. Any idea what's going on?