I installed Gentoo Linux on a separate partition to compile Gimp-2.9.1 from git sources.
First babl then gegl and then gimp.
When I ran make on gegl it errored out with this message:

Indeed I didn't have this module,never had any need for it until now.
So I reinstalled nvidia-drivers again with the necessary directive to also build nvidia-uvm module.

Uvm stands for "unified memory".
What it does afa I understand is allow programs to incorporate code by CUDA which is an nvidia
programming environment.
What gegl uses it for I have no idea.
Could be they incorporate their own code.

Now I wonder what happens when your computer has a different graphics card like radeon or intel etc.

Gerard.

Plenty of things done in Gimp would go a lot faster in a graphics card GPU. A GPU is basically several hundred processors in parallel that can run the same set of instructions on different data. A CUDA-aware Gimp would run circles around the standard one. OpenCL is a more "open" equivalent of CUDA. On the other hand, NVidia graphics cards are on the whole more Linux-friendly that their competition, and so equip a vast majority of Linux systems.