# Linux 122 — idle workers at speed

**Decision:** keep the L121 admission policy. Neither tested fast-travel relaxation met every coverage and tick limit.

Five diagnostic runs at 30 m/s had 686 idle-worker windows with near tiles missing. In 673 (98%) the expanded critical set was not ready; 462 (67%) also had Core-region compilation pending, and 441 (64%) declined an exact region-dependent near tile. These counts overlap. Far-parent, near-cap, walkable-ring, pawn-collision, and stale-center holds were all zero. Only 13 windows had pending near work and no unadmitted near tile. The desired center was current in every window.

Region compile requests scheduled immediately (request to task submission p50/p95 **0.008/0.021 ms**). UE task queue delay was **0.122/14.856 ms** p50/p95 (max 54.4 ms); task runtime was **0.485/4.572 ms**, with Core compile wall time **0.259/3.679 ms**. The task runs on UE background workers, not the Game Thread. It was submitted while generation workers were idle in 680/1,158 requests. The compile targets the current desired center; there is no velocity look-ahead. The completion gate remained pending **18.216/21.136 ms** p50/p95 while the Game Thread observed completion.

The UE/headless coverage gap is not a denominator mismatch: both use resident near tiles / desired LOD0–2 tiles, with about 1,346–1,348 desired near tiles in UE versus 1,344 in the saved headless runs. Headless was about 82.6%; UE was 45.0%. The measured idle windows point to UE admission. Apply work is small (L121 near apply and proxy p95 were about 0.20 and 0.24 ms), though worker-finish-to-apply wait reached 120 ms p95 and may add secondary delay.

| Fast-travel design | Near change | Far-hole change | Paired p99 change | Worst tick |
|---|---:|---:|---:|---:|
| Admit normal near/far shares before expanded critical readiness | +15.42 pp | −0.28 pp | +0.28 ms | 14.52 ms |
| Admit near LOD0–2 only until critical readiness | +9.89 pp | +1.48 pp | −0.56 ms | 14.38 ms |

The first design exceeded the p99 bar (worst per-run p99 13.36 ms versus L121's 11.00 ms); the second increased far holes. Both stayed under L121's 14.74 ms worst-tick ceiling. No admission behavior was retained, so arrival behavior remains L121.

UE build passed with `-NoUBA -MaxParallelActions=4`. Exact tile and whole-view hashes matched L104 in **24/24** Clang/GCC W1/W8/W12 runs. Fast tier passed (**269 gates, 5 diagnostics**). Logs are under `Saved/Linux/l122`.