# Linux 72 report

## Unreal timeline

Three L71 and three L72 traces used the same 2,850 tile keys. The readback value `streaming_background_worker_cap=1` selects the TaskGraph background lane; Unreal reported eight background workers and eight effective tile slots. The delay was queue admission and result draining, not RMC construction. Raising ready queue depth from 8 to 16 and the startup apply count cap from 12 to 24 moved readiness forward. The hard game-thread apply budget stays 14 ms, and the moving-player admission cap still prevents a ready backlog during fast travel.

| Median milestone | L71 | L72 |
|---|---:|---:|
| Last tile requested | 4.577 s | 3.680 s |
| Last worker started | 4.583 s | 3.696 s |
| Last worker finished | 4.597 s | 3.712 s |
| Last tile applied | 4.754 s | 3.724 s |
| Initial set ready | 4.775 s | 3.741 s |
| Walkable gate ready | 1.068 s | 1.107 s |
| Queue p95 | 122.7 ms | 34.8 ms |
| Request-to-apply p95 | 139.1 ms | 45.3 ms |

The worker-finish-to-last-apply tail fell from 157 ms to 11 ms. L72 per-frame apply work was p95 0.73 ms, max 6.26 ms, below the 14 ms cap; the cap was not hit. Commandlet frame interval p95 was 18.85 ms. Initial-set readiness still takes 3.74 s (about 199 p95 frame intervals), so the roughly 1 s target is not met. Against the 2.41 s headless stride-0 whole-view median, about 1.33 s remains in the Unreal path. RMC build p95 was 0.32 ms.

Headless whole-view timing used three interleaved before/after pairs per stratum:

| Stratum | Tiles | Before median | After median |
|---|---:|---:|---:|
| 0 | 2,850 | 2.538 s | 2.412 s |
| 1 | 2,249 | 6.382 s | 6.343 s |
| 2 | 2,233 | 5.718 s | 5.443 s |
| 3 | 2,329 | 2.661 s | 2.624 s |

## Passage composer

The L71 40× compares 18.8 ms for nonempty passage tiles with 0.5 ms across all LOD0 tiles; 441 of 512 LOD0 tiles were empty. Empty tiles can stop after classification, while a nonempty passage tile fills and meshes a density grid. It is not a matched per-sample comparison. These profiles do not isolate the passage-specific share of total tile time: passage controls have about twice the samples of the terrain control, and no matched nonempty terrain control was profiled. Native calls were 27,367 for terrain (17,680 samples) and 43,243/44,767 for passage tiles (36,439/37,975 samples).

Within the composer, route-mouth checks were a large avoidable scan. The shared composer now filters mouth-support segments against per-tile bounds and reuses the identical mouth relief result. Passage carve/support visits and smoothstep counts stayed the same. The exact counters are below; they show reduced work, but do not identify the dominant timed composer term.

| Tile (LOD0) | Samples | Native calls before/after | Mouth route checks before → after | Relief calls before → after |
|---|---:|---:|---:|---:|
| Terrain `(5,-2,-47)` | 17,680 | 27,367 | — | — |
| Passage `(1,0,-47)` | 36,439 | 43,243 | 612,242 → 123,090 | 384,444 → 343,414 |
| Passage `(0,1,-47)` | 37,975 | 44,767 | 1,042,612 → 131,334 | 407,910 → 364,554 |

Field calls and world hashes are unchanged. The two passage samples reduced route checks by 80% and 87%. A single instrumented worker-time comparison was mixed (100.0→91.8 ms and 155.2→157.1 ms), so it does not establish a stable per-tile wall-time gain. L71 identified near-field density-grid sampling and meshing as the largest cost; L72 does not isolate which composer term takes the most time.

## Integrity and housekeeping

- Hashes matched before/after at W1, W8, and W12 with Clang and GCC: all 2,850 keys and density, mesh, payload, and topology hashes matched.
- Fast tier passed in 270.2 s (269 PASS, 5 DIAGNOSTIC); gates and thresholds are unchanged.
- Compressed all 11 verification meshes with Python `lzma`: 78.54 MB → 18.37 MB (23.4% of original). `verify.py` expands them into its output baselines folder before use.

## Source changes

- `Source/VoxelForge/Private/VoxelWorld.cpp`: queue depth and startup apply count tuning, retaining the 14 ms hard budget and moving-player admission behavior.
- `Standalone/Core/src/ShapeWorldInternal.h`: tile-local passage support segment filtering and reused mouth relief evaluation.
- `Standalone/Core/include/VoxelForgeCore/VoxelForgeCore.h`, `Standalone/Core/src/VoxelForgeCore.cpp`, `Standalone/Source/StreamingWorld.h`, `Standalone/Source/StreamBenchmarkPipeline.h`, `Standalone/Source/StreamBenchmarkHeadless.cpp`: opt-in per-tile composer counters.
- `Standalone/Tools/verify/verify.py` and the Linux37/Linux47 audit scripts: decompressed baseline path handling.

## Failed and rejected runs

- The first Unreal build referenced unavailable .NET 8.0.300; retry with installed 8.0.412 succeeded.
- An initial hash invocation omitted `--stream-hash-tiles` and emitted no hash rows; corrected six-config matrix passed.
- The first fast-tier attempt lacked built executables, then an audit helper still read the compressed baseline path. Both were corrected; the rerun passed.
- A no-feature passage cull changed density hashes in 433 tiles and was reverted. A point-bound trial rejected no negative LOD0 samples, and a carve-seed trial added one candidate visit per query; both were dropped. A depth-32 queue probe worsened LOD0 request-to-apply p95 (102.6 ms) and walkable readiness (1.204 s), so depth 16 was retained.