I think by default glxgears has vsync enabled. But it's trivially possible to disable it with an env var. Considering the CPU usage I assume that is what was done. 60% CPU usage for running glxgears at 120Hz seems excessive.
There is no vsync with the dumb framebuffer backend I'm using. We have a real display driver, but it needs rebasing and adapting to work on these laptops (it was developed on the Mac Mini).
I always remember glxgears running at hundreds of FPS and it being used as a poor man’s benchmark. Perhaps this has changed of late though…
I always have had to set `vblank_mode=0` to get it to run as fast as possible.