GDR and gdrcopy releationship.-

[changchengx]

1. GDR stands for GPUDirect RDMA right?
2. Does gdrcopy library only for create user-space mappings of GPU memory ? Is it only supporting copying data between CPU and GPU on the same server machine?
3. If it aims to send/recv data between GPUs on the different server machines with using GPUDirect RDMA, does it need gdrcopy ?

[jdinan]

The naming is a little confusing, GDR Copy and GPUDirect RDMA are separate data movement mechanisms. GDR Copy enables the CPU to create a mapping for memory of a GPU on the same server. Using this mapping, the CPU can access the GPU's memory using direct load/store operations. GPUDirect RDMA allows a network controller to directly access the GPU's memory. GDR Copy is not required to use GPUDirect RDMA.

[lcebaman]

Yet, higher BW is achieved when GDRcopy and GPUDirect are enabled