`flush_static_gx` bakes a cell once it has been dirty and *quiet* for its
window, which staggers cells whose changes are staggered — and a world load
dirties hundreds within a few frames of each other, so their windows expire
together and the whole burst baked in one flush. A cold Elwynn vista measured
one run of 43.2 ms against 2.6 ms for the other nineteen in that second
(`WOW_SYSTEM_TIMING=1`): a visible stall, and a scheduling artefact rather than
work, since the same bakes cost the same total spread over later frames.
`BAKE_BUDGET` spends 4 ms of wall clock per flush — the figure
`terrain_stream::SPAWN_BUDGET` already paces placement spawns by, and the two
passes share a frame — and hands the rest to the next flush. A region that
yields stays `dirty` with its `last_change` untouched, so `bake_due` says yes
again next flush: yielding is the absence of a decision rather than one, which
is what keeps the budget to *when* a region bakes and never *whether*. The three
exemptions say the same thing. Nothing yields until one region has baked, so a
region larger than the whole budget cannot stall behind itself. `flush_now` gets
the full flush it asked for. The `MAX_DIRTY_FRAMES` age cap outranks the budget,
so the backstop that already bounded a region's wait stays absolute instead of
becoming advisory. And an empty region is an unload — free to publish, and
deferring one would leave dead geometry on screen — so removals are never
budgeted at all.
Measured after, same vista: every budgeted flush landed 4.0–4.5 ms, draining a
backlog that peaked at 398 held regions at ~30 a frame over 16 consecutive
flushes. Worst visible flush 43.2 → 4.5 ms.
One flush still runs 58.4 ms and should. `terrain_stream.rs:908` asks for a
`flush_now` while `!focus.paced`, because a region that cannot draw yet is "a
hole in the reveal", and `ViewFocus::paced` is false only "through entry, a
teleport and a world swap, while the loading cover absorbs the burst". So the
budget moves that stall out of play time and behind the cover, which is the
point; it is not a leftover to fix.
`WOW_GX_BAKE_MS=<ms>` overrides the budget and an explicit `0` retires it, so
the A/B runs in both directions.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SgstFWtn1RxEJ5kVrpgYwn
gromandClaude Opus 5
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