Target-model skip-topk layers reuse the previous active layer's top-k indices and should not run local indexer modules. Centralize the layer-needs-indexer decision, skip constructing indexers on shared target layers, and skip their checkpoint tensors during load while keeping nextn/draft layers conservative for state safety.
Constraint: index skip should reduce GPU memory in both prefill and decode without changing top-k propagation semantics
Constraint: nextn/draft layers report shared top-k behavior but still need local indexer state safety
Rejected: Loader-only filtering | parameters are already allocated during model construction
Rejected: Dummy indexer modules for skipped layers | preserves most of the memory cost this change removes
Confidence: high
Scope-risk: moderate
Directive: Do not reintroduce indexer execution on skip_topk target layers without proving prev_topk propagation and weight residency semantics
Tested: remote g0034 cjy-glm5-new PYTHONPATH=python python -m pytest -q test/registered/unit/speculative/test_spec_utils.py test/registered/unit/configs/test_nsa_index_layers.py test/registered/unit/models/test_deepseek_index_skip_weight_loading.py -> 19 passed
Tested: remote g0034 cjy-glm5-new py_compile for modified runtime files
Not-tested: full GLM5 model restart memory delta measurement
Pre-e2e audit fixes for NSA index-topk sharing (index_topk_pattern):
- Validate the pattern at init: F/S charset only, must start with F
(layer 0 has nothing to share from), and length must equal
num_hidden_layers — a short pattern previously crashed deep in pool
init with an obscure per-layer ValueError, a long one silently
ignored tail characters. Warn when a pattern shadows a configured
index_topk_freq (pattern takes precedence silently otherwise).
- Fail fast when a shared (S) layer receives prev_topk_indices=None:
both gated indexer call sites previously fell through to omitting
topk_indices entirely, running sparse attention without indices and
silently corrupting output if threading were ever dropped.
- Reject pipeline parallelism with index-topk sharing (same rationale
as the existing TBO guard): topk indices are not threaded across
PP-stage boundaries, and each stage's loop resets them to None.
- Gate the CP shared-KV index prefetcher on the next layer having an
index-cache slot: prefetching an S layer's nonexistent buffer
tripped the inactive-layer fail-fast and disabled the prefetcher
for the entire run on the first F->S transition.
- Log the resolved active index layer plan at pool init so an e2e run
can confirm IndexCache is actually on.
Tests: pattern validation cases incl. the GLM-5 reference 78-char
pattern, next_skip == skip-of-next invariant; existing 'C' pattern
test updated to upstream 'F' charset.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Centralize the IndexCache skip formula and thread the resulting active logical index layers into NSA KV pools. HiCache now skips only the indexer H2D/D2H payload for inactive target layers while preserving per-layer MLA KV transfer, keeping allocation shape unchanged for this phase.
Constraint: P0-P2 must not compact device or host allocation yet; prefill/decode state transfer still has no logical layer-id metadata.
Rejected: Recompute the skip formula separately in mem_cache | formula drift would corrupt cache or waste transfers when offset/pattern settings change.
Rejected: Skip whole-layer HiCache load/backup | MLA KV remains required for every attention layer.
Confidence: medium
Scope-risk: moderate
Directive: Before enabling compact state buffers or compact allocation, add layer-id metadata validation to PD transfer.
Tested: Local py_compile for touched files; remote pytest in g0034 container: test_nsa_index_layers.py and TestNSAIndexerPageIndices, 20 passed.
Not-tested: ETE replay/GSM8K with --nsa-index-topk-freq 4; PD state-transfer compaction remains unimplemented.
laoyao0822
leaveletandClaude Fable 5