The remaining ~21 ms display stage was the conservative release target: the
presenter aimed at the first frame timeline whose DEADLINE was still ahead,
and the platform's deadline budgets for GPU rendering the app has yet to
submit (presDeadline = 11.3 ms on the A024 — more than a full 120 Hz
period). A decoded video buffer has no GPU work left; its only real
constraint is SurfaceFlinger's own latch lead. Every frame paid a whole
extra refresh of waiting for a budget it never used.
next_target now gates (and subdivides) on the timeline's EXPECTED PRESENT
minus a 4 ms latch margin; the glass budget reopens at that latch instant
(expected present − margin) rather than the deadline, which under the
aggressive gate can already lie in the past — an instant reopen would let
two releases pile onto one vsync. A mis-gamble presents one vsync later,
which is exactly what the deadline gate paid on every frame — the trade is
one-sided.
On-glass (A024, 2800×1260@120 HDR, game load): latch p50 21→8-10 ms,
display 26,3→9,5 (pace 0,8 + latch 7,7), e2e 43,7→26,4 p50 / 29,2 p95,
released=displays=120, paced≈0, forced=0. The latch now sits under one
refresh interval — the vsync-latch floor.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehlerandClaude Fable 5
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