On hardware a thread waiting for vblank returns ~53us after it, where we
had it back in ~5us, and the first of four waiters runs after ~85us: each
waiter beyond the first adds ~9us (pspautotests threads/scheduling/
vblankwake). The waiters are now released by a separate event 48us + 9us
per extra waiter after the vblank. Which vblank a wait is for is still
decided at the vblank, so a thread that starts waiting in between still
waits a whole frame (sceDisplay section version 8).
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>