I tried it today, installing optimus-manager and rebooting the machine automatically switched to integrated mode. After the reboot the following showed as output of nvidia-smi:
$ nvidia-smi
Fri Aug 6 13:43:47 2021
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 470.57.02 Driver Version: 470.57.02 CUDA Version: 11.4 |
|-------------------------------+----------------------+----------------------+
| 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 NVIDIA GeForce ... Off | 00000000:01:00.0 Off | N/A |
| N/A 33C P0 N/A / N/A | 0MiB / 4042MiB | 1% Default |
| | | N/A |
+-------------------------------+----------------------+----------------------+
+-----------------------------------------------------------------------------+
| Processes: |
| GPU GI CI PID Type Process name GPU Memory |
| ID ID Usage |
|=============================================================================|
| No running processes found |
+-----------------------------------------------------------------------------+
And running several other commands indicated that the iGPU was in fact being the one in use:
$ optimus-manager --status
Optimus Manager (Client) version 1.4
Current GPU mode : integrated
GPU mode requested for next login : no change
GPU at startup : integrated
Temporary config path: no
$ optimus-manager --print-mode
Current GPU mode : integrated
$ optimus-manager --print-next-mode
GPU mode requested for next login : no change
$ optimus-manager --print-startup
GPU at startup : integrated
Compiling and running a program that is meant to use CUDA works in integrated mode:
$ nvcc fw.cu
$ ./a.out &> /dev/null &
[1] 2717
$ nvidia-smi
Fri Aug 6 13:48:11 2021
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 470.57.02 Driver Version: 470.57.02 CUDA Version: 11.4 |
|-------------------------------+----------------------+----------------------+
| 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 NVIDIA GeForce ... Off | 00000000:01:00.0 Off | N/A |
| N/A 42C P0 N/A / N/A | 49MiB / 4042MiB | 99% Default |
| | | N/A |
+-------------------------------+----------------------+----------------------+
+-----------------------------------------------------------------------------+
| Processes: |
| GPU GI CI PID Type Process name GPU Memory |
| ID ID Usage |
|=============================================================================|
| 0 N/A N/A 2140 C ./a.out 47MiB |
+-----------------------------------------------------------------------------+
I haven’t tested HDMI on integrated mode yet, but I will very likely not be needing it anyways.
Is there any way that, without additional hardware, I can test the power consumption of my dGPU accurately, to ensure that it is in fact powered off?