I did some experiments with vsync: VSYNC ON: 60 fps, 6% of 1 CPU core. VSYNC OFF: 150 fps, 100% of 1 CPU core. I profiled the run, and with vsync off, I see glXSwapBuffers() take 96% of the CPU cycles. The FPS delta (150/60) is just a factor 2.5 so it would be doing, at most, 2.5 times the work …

glXSwapBuffers() gobbling up a full CPU core when vsync is off

stolk October 9, 2020, 4:14pm 2

UPDATE

Adding a glFinish() before the swap buffers does not help.

Using __GL_YIELD=USLEEP will however, make CPU usage drop from 100% of a core, to 20% of a core.