systemWideAtomics cudaMalloc cudaFree cudaMemcpy cudaFreeHost whole ./ ../ ../../Common Atomic Intrinsics Unified Memory CUDA GPGPU system-wide atomic true systemWideAtomics.cu UVM 1:CUDA Basic Topics sm60 sm61 sm70 sm72 sm75 sm80 sm86 x86_64 linux ppc64le linux 6.0 exe