I use Blender as a video montage software and the issue happens during rendering.
Blender doesn't use all the cores of the machine. In fact it uses only one. However, I set the threads value to fixed 8.
And I still have a single thread rendering.
I thought I could find the answer here but obviously it's not the same problem.
The GPU is unemployed too.
Who knows how to use the whole machine?
Edit: I precise that I use Linux and other softwares work fine with multithreading.