Performance mode (p0) does not automatically downshift to idle (p8) (driver 440.44 ubuntu 18.04)

After having updated my headless gpu server (4 GTX 1080Ti) to the latest nvidia drivers v440.44, the performance mode of my 4 GPUs when not used is stuck to P0. I do not have any X11 folder (headless server) and I tried the following options into a new /etc/modprobe.d/nvidia.conf file (i ve created)

options nvidia NVreg_RegistryDwords=“PowerMizerEnable=0x1”
options nvidia NVreg_DynamicPowerManagement=0x02

and i applied these changes by doing this

sudo modprobe -r nvidia_drm nvidia_modeset nvidia
sudo modprobe nvidia_drm nvidia_modeset nvidia

But still the same pb. Any idea ?

Thanks!