A long cold-request workload flooded the prefill log (~177MB / 32K lines in 8min, all 8 CP ranks) with cp_host_reservation_plan_insufficient + prepare_write_backup_reservation_failed even though the host pool was <42% used and the writes physically fit. Root cause: _free_room_deficit folds the proactive 20% free-room target (hicache_host_free_room_ratio) into the admission deficit once a lane dips below the 10% trigger. _evict_cp_host_for_write_admission then failed -- and evicted nothing -- whenever it could not reclaim that full 20% target, which is impossible while the residual is locked/pending. The lane never drained, so every subsequent backup re-issued the same impossible demand and re-logged on every tick. The reservation failure is itself a graceful skip, so there is no crash; the symptom is the log storm. Gate write-backup admission on the HARD deficit -- max(0, required-available) over the target and draft lanes (draft_available is 2**62 with no draft pool, a no-op) -- and evict toward the watermark best-effort, admitting whenever the write itself fits. This drains the stuck lane and backs the request up instead of skipping+flooding. The proactive watermark stays as the eviction target (deficit_by_owner unchanged); it is no longer a hard admission gate. The decision is computed from rank-replicated state on the collective-free reserve path, so every CP rank makes the same admit/skip choice (opus-reviewed rank-safe). Also rate-limit the four host-reservation fallback warnings (once per 10s per fallback_name, with a suppressed count) so any genuine exhaustion degrades quietly instead of producing a log storm. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Registered Tests
Tests under this directory are auto-discovered by run_suite.py via CI registration decorators.
Where Should I Put My New Test?
No server / engine launch required
| What you're testing | Directory | Requires |
|---|---|---|
| Component logic in isolation (cache, scheduler, config, parser, etc.) | unit/<module>/ |
CPU or GPU |
| CUDA kernel correctness | kernels/ |
GPU |
Server / engine launch required (E2E)
| What you're testing | Directory | Requires |
|---|---|---|
| Model inference correctness | models/, 4-gpu-models/, 8-gpu-models/ |
GPU |
| Feature-specific (OpenAI API, LoRA, speculative, distributed, VLM, etc.) | openai_server/, lora/, spec/, distributed/, ... |
GPU |
| Benchmarks (performance, accuracy, stress) | benchmark/ |
GPU |
| Platform-specific | amd/, ascend/ |
Vendor GPU |
See unit/README.md for unit test conventions.