@Alberto:

Sorry for the lateness of my reply, apparently Launchpad doesn't
automatically subscribe me just because I commented...

Anyway, I am attaching both gpu-manager.log and gpu-manager-switch.log
for when both the Nvidia profile and Intel profiles are selected.

FWIW, I discovered that once I select the Intel profile I can use
bbswitch to shut the card down for full power saving. This behavior
remains constant regardless of whether I have TLP running or not.
Powertop shows the Nvidia card tunable set to "Good" even without TLP
running.

As far as I can tell, the issue seems to be that on my hardware the only
way to shut the card down completely is through a dedicated ACPI message
(i.e., what bbswitch does) rather than "normal" PCIe power management.

Let me know if I need to do anything else, this laptop is not essential
for productivity so if I need to try to break stuff I'm up for that.

** Attachment added: "gpu-manager-logs.tar.xz"
   
https://bugs.launchpad.net/hwe-next/+bug/1778011/+attachment/5233964/+files/gpu-manager-logs.tar.xz

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https://bugs.launchpad.net/bugs/1778011

Title:
  SRU: PRIME Power Saving mode draws too much power

Status in HWE Next:
  New
Status in gdm3 package in Ubuntu:
  Fix Released
Status in nvidia-graphics-drivers-390 package in Ubuntu:
  Fix Released
Status in nvidia-prime package in Ubuntu:
  Fix Released
Status in nvidia-settings package in Ubuntu:
  Fix Released
Status in sddm package in Ubuntu:
  Confirmed
Status in ubuntu-drivers-common package in Ubuntu:
  Fix Released
Status in gdm3 source package in Bionic:
  Fix Released
Status in nvidia-graphics-drivers-390 source package in Bionic:
  Fix Released
Status in nvidia-prime source package in Bionic:
  Fix Released
Status in nvidia-settings source package in Bionic:
  Fix Released
Status in sddm source package in Bionic:
  Confirmed
Status in ubuntu-drivers-common source package in Bionic:
  Fix Released

Bug description:
  SRU Request:

  [Impact]
  Relying on the nouveau driver and on the vga switcheroo (to get around a 
change in systemd LP: #1777099) caused increased power consumption, and slowed 
down the switching process.

  Furthermore, if the main X/Xwayland session was started by Gdm when
  the nvidia driver was loaded, the session will keep the nvidia module
  loaded, and prevent the system from switching off the dGPU. Also, the
  nouveau driver will be loaded, if nvidia is not, and this can cause
  problems to unsupported NVIDIA GPUs.

  The solution involves the following changes:

  1) Solving the problem in systemd (LP: #1777099)

  2) Adding code in gpu-manager and in nvidia-prime to unload the nvidia
  modules, and to allow the PCI device to sleep.

  3) Making a slight change to the current patch in Gdm, used to call
  the PRIME scripts before and after a Gdm session (so that gpu-manager
  gets actually called on log out)

  4) Adding code in gpu-manager to kill the main X/Xwayland session on
  log out, if the session is preventing us from unloading the nvidia
  driver. A new X/Xwayland session will be created after unload the
  module.

  5) Removing the systemd service that loads nouveau from the nvidia
  packages.

  [Test Case]
  1) Enable the -proposed repository, and install the new 
"ubuntu-drivers-common", nvidia drivers, nvidia-prime, and gdm3 *

  2) Make sure the nvidia packages are installed, and enable performance mode 
(if it is already enabled, call "sudo prime-select intel" first):
  sudo prime-select nvidia

  3) Restart your computer and attach your /var/log/gpu-manager.log. see
  if the system boots correctly. If unsure, please attach your /var/log
  /gpu-manager.log and /var/log/Xorg.0.log

  4) Select power saving mode:
  sudo prime-select intel

  5) Log out and log back in

  6) Check if the nvidia driver is still loaded:
  lsmod | grep nvidia

  [Regression Potential]
  Low, as hybrid graphics support does not work correctly, and the changes only 
affect this use case.

  _____________________________________
  * Steps to test the updates:

  1) Enable the bionic-proposed repositories

  2) Create /etc/apt/preferences.d/proposed-updates with the following
  content:

  Package: *
  Pin: release a=bionic-proposed
  Pin-Priority: 400

  3) Update the list of packages:

  sudo apt-get update

  4) Install the packages from -proposed using the following command:

  sudo apt install nvidia-driver-390/bionic-proposed gdm3/bionic-
  proposed ubuntu-drivers-common/bionic-proposed nvidia-prime/bionic-
  proposed nvidia-settings/bionic-proposed libnvidia-gl-390/bionic-
  proposed libnvidia-compute-390/bionic-proposed libnvidia-decode-390
  /bionic-proposed libnvidia-encode-390/bionic-proposed libnvidia-
  ifr1-390/bionic-proposed libnvidia-fbc1-390/bionic-proposed

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