The 2.5 ms submit margin ahead of expected present assumed
SurfaceFlinger latches well before the vsync. On-glass (NP3, 120 Hz)
that lead is not needed: with the margin at zero every release still
made its vsync (paced=0 across full sessions) - meaning the constant was
2.5 ms of pure display latency on every frame, and it was quantizing
away exactly the readiness gains the slice-overlap pipeline just bought.
e2e on the Linux-host pairing dropped from 22-24 ms to 14-18 ms.
The margin is now adaptive instead of assumed: it starts at 0 and only
widens (+500 us per 1 Hz window, capped at the old 2.5 ms) when the
paced counter shows real latch misses - one-way per stream, so a margin
that proved necessary is never re-gambled mid-session. A device that
needs lead converges within seconds; a device that doesn't keeps the
full win. debug.punktfunk.latch_margin_us (0..=8000) pins the margin
for rebuild-free sweeps, and the presenter logs the resolved mode at
stream start.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehlerandClaude Fable 5
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