Comment 98 for bug 1814125

Although not entirely the same.

Mutter was already trying to do things right (compared to KDE) so if __GL_MaxFramesAllowed=1 helps you then that suggests to me the issue is missing frame notifications from the backend/driver (COGL_FRAME_EVENT_SYNC/COGL_FRAME_EVENT_COMPLETE). If they are unsupported or absent then clutter_stage_cogl_schedule_update returns early and the clutter master clock would revert to a dumb fallback throttling method (which is the same as KDE's).

This also explains why reverting 383ba566b would seem to help some people. It's a workaround, but not a fix for the real problem.

I guess what we need now is a developer who can reproduce the problem (I can't) to find out why COGL_FRAME_EVENT_SYNC/COGL_FRAME_EVENT_COMPLETE events aren't arriving. Note: Arriving 150ms+ late is counted the same as not arriving, so that's possible too but would be extra strange.