Really slow output when screens not unified


When running with my HDMI screen and the laptop screen (with brightness at 0 because i don’t need it in that configuration), both with the unified screen option, I have good performances.
But when I disable my laptop screen to just output to my HDMI screen, performance are abysmal.

I try that to lower the energetic consumption (there is a slight increase when outputs are unified, and I though a slight decrease of performance as well).

So, is it expected?

the nvidia bug is the same as my last question:
nvidia bug report

is it related to that line in my bashrc?

xrandr --setprovideroutputsource NVIDIA-G0 modesetting && xrandr --auto


That’s a bug in the modesetting driver that’s been fixed but your xorg package is too old so doesn’t contain the fix.

Thanks generix, I will ask the debian maintainers then

I tried installing the latest xorg available in Debian testing by preparing a local backport SimpleBackportCreation

  • x11-common 7.7+23
  • xbase-clients7.7+23
  • xorg-dev7.7+23
  • xorg7.7+23
  • xserver-xorg-input7.7.23
  • xserver-xorg-video-all7.7+23
  • xutils7.7+23

But the issue still occurs.

Which package is missing to make it work please?


xserver-xorg-core contains the modesetting driver.

Backporting so many packages is a hassle, I will switch to sid.

Thanks Generix


I 've just reinstalled my system using Debian testing because I cannot afford to put Sid on my dev machine.
But the packages are the mostly the same.

The issue remains.
nvidia-bug-report.tar.gz (226.4 KB)

It is as if it was software rendered. One click takes ages to show its effect.

and that line in my bashrc:

xrandr --setprovideroutputsource NVIDIA-G0 modesetting && xrandr --auto

Xserver/modesetting driver should be fine, containing the fix. Please post the output of

sudo cat /sys/module/nvidia_drm/parameters/modeset

it says “Y”

The fix was merged on 2021-04-16
so any Xorg server 21.x should work.
Can you upgrade the nvidia driver to something more recent?

you mean the 515 (from nvidia directly)?

Yes, only other option besides 470 with kernel 5.18.

ok I will do that right now :)

On the bright side with 515: the HDMI screen is working fine, but the laptop screen will go black with the dash → “_” on the upper left side of the screen.

The laptop screen is perfectly working during the boot and halt phase. But coming at the login prompt, it stays black.
The HDMI screen works perfectly when the laptop one doesn’t.
If the hdmi screen is unplugged, the laptop screen will keep being black with the underscore top left…

In the display configuration, the laptop screen is not detected.

options nvidia-drm modeset=1


blacklist nouveau
options nouveau modeset=0

nvidia-bug-report.tar.gz (217.1 KB)

(good night)

Please delete /etc/X11/xorg.conf

Yes! It is working properly now.

Thanks, again, generix ;)

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