Dear Maintainer,

enabling an external display using the integrated Intel chip as the primary GPU
leads to steady high CPU load caused by the Xorg process.

This is on a system (see [0], [1]) where the external ports are connected to
the dedicated NVIDIA GPU. The dedicated GPU acts as a sink for the integrated
CPU, dubbed "reverse PRIME" (see [2]).

I expect the CPU should not to be involved in painting to the external display.
Different resolutions cause different loads. For my setup, a low resolution
(640x480) lead to 15% steady load, higher resolutions (4K) lead to upto 70%
load.

This is with or without a compositor involved. There is no higher load using
either only the internal display or using an external display using the
dedicated NVIDIA GPU as the primary GPU.

Setting the driver to "modesetting" or using no xorg.conf at all makes no
difference.

Regards,

Johannes

[0] https://wiki.debian.org/NVIDIA%20Optimus
[1] https://wiki.gentoo.org/wiki/Razer_Blade_Pro_(2019)#External_graphics
[2] https://forums.developer.nvidia.com/t/the-all-new-outputsink-feature-aka-reverse-prime/129828