Dear JerryHong,
Yes, “GR3D_PCI” means the discrete GPU engine.
This is only way to check dGPU usage so far.
There is a sample called deviceQuery if CUDA has been installed on your DPX2. Run this sample, it will list GPU usage info in detail:
cd /usr/local/cuda-8.0/samples/1_Utilities/deviceQuery
sudo make
sudo ./deviceQuery
Thanks.