Preliminarily, this appears to be the result of the “HardDPMS” being on by default as of the 440 driver, while running headless, and can be alleviated by an option in the xorg.conf, as shown in these two references:
- 440.36 with Bumblebee drops to ~1 FPS after running for 10 minutes - #5 by aplattner
- VirtualGL | Documentation / Headless nVidia Mini How-To
So far, I’ve been able to run for 2 hours with either the 440 or 450 driver, with no slowdowns, whereas I saw slowdowns within 15’ish minutes previously.