GPU is always awake even without persistence mode


I have an Ubuntu 20.04 workstation with two RTX 3090 GPUs installed.
Originally, GPUs remained slient when they are not used, and nvidia-smi took a few seconds to wake GPUs up. Namely, we were not using persistent mode.
However, suddenly GPUs started to become awake regardless of the persistent mode and nvidia-smi returns instantly even though persistent mode is off.
It is suspected that a recent kernel update caused this, but I cannot even determine where I should look to fix this issue.
Any advice would be appreciated. (Kernel rollback cannot be our option.)