NVidia: Better performance with nouveau drivers than with proprietary drivers?

Question

I'm testing an Asus UX430UQ under Ubuntu. It has an NVidia 940MX graphics chip in it. I'm using Lightworks to benchmark performance, and the numbers are coming up heavily in favour of the open source nouveau drivers over the proprietary ones in 4 of the 5 benchmarks.

I ran a bunch of tests with each of the drivers enabled (rebooting after switching the driver), discarded outlier values, and averaged the results of each benchmark for each driver.

Nouveau
host to GPU: 998.1fps
GPU to host: 516.4fps
shader: 89024.87fps
playback: 342.24fps
render: 192.22fps

Proprietary
host to GPU: 208.41fps
GPU to host: 251.66fps
shader: 142293.05fps
playback: 181.75fps
render: 37.12fps

So other than shader performance at 60-70% of the proprietary result, the open source drivers appear to outperform the proprietary drivers by 2-5 times.

I've also found that real performance during playback of a particular section of an edit is noticeably worse with the proprietary drivers: there are some occasional dropped frames and audio glitches like I experience when playing the same section of that edit on my 2012 MacBook Pro.

Is there a reason why the open source drivers would be overall faster than the proprietary ones? Are these benchmarks misleading in some way? Have others seen similar results? Should I just use the open source drivers?

EDIT: Based on @Ken's suggestion, I checked the PRIME profile in NVIDIA X Server Settings. It had been set to NVIDIA. Switching it to Intel (and logging out and back in) and running the Lightworks GPU benchmarks again gives results that closely match the open source result, suggesting that the nouveau drivers were simply using the integrated graphics:

host to gpu: 969.2525
gpu to host: 516.655
shader: 87600.006667
playback: 337.516
render: 191.4125

I suppose some of these results make sense — host to GPU and vice versa, at least, should be fast since the chip is integrated into the CPU; better shader performance from the NVidia chip is to be expected. I would have thought that dedicated graphics would be faster for the render test, though.

Answer 1

You said that you have an Asus UX430UQ which means it has an integrated GPU as well as a dedicated GPU. What I think is happening when you install the proprietary drivers, it is using the integrated GPU instead of the dedicated GPU.

In your NVIDIA X Server Settings, you should have a window that looks like this which will let you change which GPU you use:

I believe you would need to log out and back in in order for the change to take effect.