Cursor effects, buffer cross-fades and inline video each ran on their
own Lisp timer, and each timer presented on its own. With everything
active that stacked presents well above the refresh rate, which is
exactly the pressure under which radeonsi was caught presenting stale
swapchain buffers, and the blocking swaps starved the other timers
(inline video dropped from 30fps to ~20fps with its tick slipping to
49ms).
Replace the three timers with a single pump. gpu.el now runs one
repeating timer that calls the new gpu-pump-tick primitive: the driver
advances the cursor physics, the fade clock and the video upload
together and presents AT MOST ONCE per tick, under the same 12ms
last-swap throttle as before. The pump paces itself: 60Hz while a
fade runs, 30Hz otherwise, gone when nothing needs it. A skipped
subsystem loses nothing -- the fade and the video are composited by
every present, whoever issues it.
The old per-subsystem entry points (gpu-anim-tick, gpu-transition-tick,
gpu-video-tick) remain for compatibility; gpu-video-tick now presents
only when a fresh frame arrived or the rect moved, under the same
throttle, instead of unconditionally.
On Metal the pump consolidates the same two timers; the animator
already coalesces presents, so the change there is one deterministic
tick (video frame pull, then animator step) with a real elapsed dt.
Measured on the AMD iGPU test box (1920x1080, Cinnamon): video tick
median 33.0ms / p90 33.3ms (was 49ms), a 30fps file plays at 29.5fps,
and worst-case contention (video + cursor effects + 12 cross-fades)
peaks at 8 presents per 100ms window with a 16.1ms median gap.
GL_LOG_PRESENT now also traces the pump decisions and the per-tick
video upload state.
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andros
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