I am using Blender 2.69 from the Linux Mint Software Manager on a system with a GTX 950, just checking to see if it will recognize CUDA. After some work, I've gotten the CUDA drivers from Nvidia installed and now there is an option to use CUDA as the compute device in the user preferences. I also selected GPU compute in the properties panel. I rendered a short, one minute clip of video using Cycles Render and monitored my GPU usage in Nvidia X Server settings. It didn't seem like the GPU was being used much (hovering 5-10%) but the video did render a little quicker than I expected.
How can I know for sure if Blender is using my GPU to the fullest to render?