Lowest Power State possible with PRIME render offload configuration

[valdotdev]

Hi there!

Just recently switched to the Nvidia hybrid graphics to enable PRIME render offload from my usuall full PRIME set up switching between intel mode and Nvidia mode . My question is this:

What is the lowest possible power state for this type of configuration? Just for my peace of mind.
I was monitoring the P-states via watch -n1 nvidia-smi and the lowest I can get at idle was P8 with 1W power consumption

+-----------------------------------------------------------------------------+
| NVIDIA-SMI 450.57       Driver Version: 450.57       CUDA Version: 11.0     |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|                               |                      |               MIG M. |
|===============================+======================+======================|
|   0  GeForce GTX 1650    Off  | 00000000:01:00.0 Off |                  N/A |
| N/A   42C    P8     1W /  N/A |      5MiB /  3914MiB |      0%      Default |
|                               |                      |                  N/A |
+-------------------------------+----------------------+----------------------+

+-----------------------------------------------------------------------------+
| Processes:                                                                  |
|  GPU   GI   CI        PID   Type   Process name                  GPU Memory |
|        ID   ID                                                   Usage      |
|=============================================================================|
|    0   N/A  N/A       872      G   /usr/lib/Xorg                       4MiB |
+-----------------------------------------------------------------------------+

Also, when checking powertop the Nvidia GPU has a usage of “100%”:
100.0% PCI Device: NVIDIA Corporation TU117M [GeForce GTX 1650 Mobile / Max-Q]

Is this normal for a PRIME render offload setup?

Thanks!

[valdotdev]

After a bit of searching around, PRIME render offload does not seem to completely power off the dGPU even if you set options nvidia "NVreg_DynamicPowerManagement=0x02" (I’m assuming in PRIME render offload xorg needs to use the dGPU) unless you’re using something like the optimus-manager in hybrid mode then the nvidia option can potentially suspend the dGPU. When doing cat /proc/driver/nvidia/gpus/0000:01:00.0/power Video Memory should be in suspend state and not Active which in this setup its always active. The nvidia option just helps the dGPU go into it’s lowest power state when not in use.

Could someone confirm my assumptions?

[valdotdev]

I finally found what’s keeping my GPU from suspending and it was really stupid of me. I’ve set up a kargos script to probe the Nvidia GPU for the temperature to display in my task bar. It keeps querying nvidia-smi. God that was embarrassing. All good and the dGPU is at 0% in powertop when not in use. Marking as solved.