View card usage:
nvidia-smi
Set tensorflow-demand resources:
import os
os.environ["CUDA_DEVICE_ORDER"] = "PCI_BUS_ID"
os.environ [ "CUDA_VISIBLE_DEVICES"] = "1" # using the GPU second block (starting with 0)
gpu_options = tf.GPUOptions(allow_growth=True)
sess = tf.Session(config=tf.ConfigProto(gpu_options=gpu_options))