[Bf-cycles] Question about NVIDIA GPU resources capping when rendering

[Impossible 3D]

Hello there,

I got a question (well, maybe it will end up as more something to add to 
a wish list/feature list; btw, Campbell also redirected me to his and 
Thomas nice (and quite recent!) podcast, good idea to check it out at 
http://blender-podcast.org/?p=479). I did enjoy listening to Campbell 
explain his point of view on the "laws of features" for Blender.

So, as I was saying in #blendercoders, it would be nice to have a 
feature to cap the nvidia gpu ressources when rendering, otherwise when 
rendering a complex scene/animation through GPU, it just spikes without 
warning, and devices (mouse, gnome ui, even a simple terminal) start 
lagging enormously, actually almost preventing use of the computer (in 
this case  i7 3ghz  with Ubuntu 12.04 LTS 64-bit - 24GB ram and GTX560 
[with 2gb ram onboard] ) until the render is complete. As soon as the 
render is complete, no lag can be seen anymore, that is, until a new 
frame starts rendering, and then it starts lagging again...

I was wondering if someone knew if resources capping was available in 
the nvidia driver and if Blender could maybe get control over it which 
would allow such a feature (I was putting forward a suggestion that a 
textbox option besides the "GPU compute" option that would allow for a 
maximum percent value to be entered and thus would allow some sort of 
control by the user, for example during the day it would render frames 
at 60-80% GPU (and hopefully, the computer would stop lagging), and at 
night or when afk for a long time, it would go back at 100% GPU). It may 
not even need this level of granularity in case it's a pain to 
implement, even a low/medium/high/unrestricted selector would be most 
welcome.

What I do not know is, maybe GPU resource capping is not even possible 
in Linux, and so Blender would have no way to have control over it. But 
maybe it is possible, if so it would be very useful to have imho 
(performance control, some heat control, huge time saver, and an overall 
better general user experience). The other possibility is maybe it can 
be done externally through a nvidia-smi command, like -gom or 
-compute-mode, or maybe another parameter that blender could trigger? I 
do not know.

Any ideas?
Many thanks!