The User Guide, Version: 3.6.1, gpu-pac section says this about making changes to GPUs under load:
For Type Pstates cards, while changes to power caps and fan speeds can be made while the GPU is under load, for
gpu-pac to work properly, other changes may require that the GPU not be under load, i.e., that sclk
P-state and mclk P-state are 0. Possible consequences with making changes under load is that the GPU become
stuck in a 0 P-state or that the entire system becomes slow to respond, where a reboot will be needed to restore
full GPU functions. ... Again, save PAC changes to clocks, voltages, or masks only when the GPU is at resting state (state 0).
For Type CurvePts cards, although changes to P-state masks cannot be made through gpu-pac, changes to all
other fields can be made on-the-fly while the card is under load.
While this once was true, I now find that Pstates card parameters (p-state masking) can be changed while under load; at least with a system running Ubuntu 20.04.2, kernel 5.8, AMDGPU 21.10, and RX 570 cards. I'd offer an update to the Guide, but I don't know with which upgrade(s) this difference occurred or how generalizable it is.
csecht
commented
2 years ago
The User Guide, Version: 3.6.1, gpu-pac section says this about making changes to GPUs under load:
While this once was true, I now find that Pstates card parameters (p-state masking) can be changed while under load; at least with a system running Ubuntu 20.04.2, kernel 5.8, AMDGPU 21.10, and RX 570 cards. I'd offer an update to the Guide, but I don't know with which upgrade(s) this difference occurred or how generalizable it is.