The LPF direct-kernel work exposed an allocation-dependent performance boundary: layer-page-first reduces descriptors only when host pages have contiguous extents. Capture the benchmark evidence and owner-lane allocator interpretation so future changes do not rediscover the same constraint.
Constraint: Current CP compute-owner allocation selects pages by modulo owner lane, e.g. (page_id - 1) % cp_size.
Rejected: Document LPF as an unconditional production improvement | random and owner-lane same-layout benchmarks are neutral without compact allocation.
Rejected: Treat owner_lane benchmark as full allocator replay | it models the modulo-lane constraint, while free/release history can add fragmentation.
Confidence: medium
Scope-risk: narrow
Directive: Tie any production LPF switch to compact/extent-aware host allocation or gather/staging support.
Tested: Local doc marker check for C115/C116/C117.
Tested: Remote tai-kernel CUDA pytest for the referenced kernel/test changes -> 45 passed in 2.52s.
Not-tested: Full SGLang ETE after changing host allocation policy; no such policy change is included.
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