[Model][PP] Validate DeepSeek-V4.1 sharing dependencies before construction

[0z5a]

Validate DeepSeek-V4.1 KV/index/top-k/candidate dependencies before constructing pipeline layers, reject invalid stage cuts with source/consumer details, and allocate projected cache groups only for local layer names. The latest update also carries the slot-row bounds guard and V4.1 prefill-workspace initialization required by the validated PP2 serving configuration.

Main sync (2026-09-14): current head c9e76fdfce983276450d8e40eb7791e30190e9db merges main at 663d7f679eda78a8d48613dfede8a4b4bcff2b74. The previous feature patch and upstream integration are preserved, with model paths and test imports updated from deepseek_v4_1 to deepseek_v41. Normalized added/removed patch lines are identical. Changed-file pre-commit hooks (.venv/bin/pre-commit run --files for every final PR file), Python parsing and git diff origin/main --check passed. The pipeline validation CPU suite passed 11 tests. CUDA compilation, GPU execution and full-model evaluations were not rerun; the model/performance evidence below remains historical. AI assistance was used for conflict resolution and validation.

Test Result

End-to-end outcome

Item	Recorded details
Observed result	The repaired TP2×PP2 configuration observed +43.98% / +47.15% output throughput at 512 / 2048 input tokens.

Output throughput

Input → output tokens	Baseline (tok/s)	Candidate (tok/s)	Throughput change
512 → 128	13.2953	19.1430	+43.98%
2048 → 128	7.8010	11.4790	+47.15%

Mean end-to-end latency

Input → output tokens	Baseline E2E (s)	Candidate E2E (s)
512 → 128	38.422	26.687
2048 → 128	65.387	44.426

Comparison setup

Item	Recorded details
Baseline	Baseline: frozen #56221 source 4f8b7e3872b878e76bffff2b46a03173961f89a5, TP2×PP2 with 20/20 layers, 8 GiB requested weight offload.
Candidate	Latest: the same partition and fixed 4 GiB KV cache, plus slot/prefill repairs and 4 GiB requested weight offload.
Attribution	This is a code-and-configuration comparison; there is no same-offload A/B that isolates the code's contribution.

Deployment reference	512-input tok/s	2048-input tok/s
Measured TP4	23.1467	13.5691
Latest TP2×PP2	19.1430	11.4790
PP throughput relative to TP4	−17.30%	−15.40%

Item	Recorded details
Deployment interpretation	The result improves the tested PP path; it does not establish a throughput advantage over TP4 or a capacity limit that TP4 cannot meet.

Correctness and regression checks

Validation	Latest result
V4.1 prefill workspace GPU regressions	2/2 passed
Full-model short QA	6/6 correct
Serial / fixed-input / concurrent token comparisons	4/4, 6/6, 4/4 matched the baseline
Timed requests	16/16 per input length, zero failures, 2048 generated tokens each
Pure dependency validation	11 CPU cases passed on the isolated source
Publication checks	11/11 CPU dependency cases; all applicable changed-file pre-commit hooks, Python parsing and whitespace checks passed

Earlier attempt

Item	Recorded details
Untimed failure	The earlier 4 GiB attempt without the prefill repair had one concurrent first-token mismatch and did not enter timing.
Evidence retention	That failed attempt is preserved; the table reports the later fully passing candidate.

Configuration, commands and scope

Setting	Recorded configuration
Model and checkpoint	Official deepseek-ai/DeepSeek-V4.1-Flash, checkpoint revision df42c109f1defefcbfcedbe7d905718a12266e40
Hardware	one node, 4×H100 SXM 80 GB with NV18 links
Runner	V1 eager
Expert parallelism	EP with allgather_reducescatter
Engram placement	Engram CPU offload
KV cache	fixed 4 GiB KV cache per worker
Scheduler limits	max context 4096, batched tokens 512, max sequences 4
Request protocol	Each workload uses random inputs, seed 42, concurrency 4, exactly 128 output tokens with EOS ignored, four separate warmup requests and then a prefix-cache reset before 16 timed requests.
Timing boundary	Startup is excluded.

Measurement scope

Item	Recorded details
Comparison design	These are single non-interleaved comparisons against recorded baselines, without repeated A/B, A/A or confidence intervals.
Output checks	Token checks cover the listed prompts; log probabilities can differ and these checks are not a standard model-quality evaluation.
Latest-tree coverage	The complete rebased main tree was not rerun on GPU.
Source receipts	The attached source correspondence distinguishes matching repair code from pre-existing main differences.

The bounds guard is adapted from existing #54296, preserving V2 mapping_enabled. The prefill initialization applies the V4.1 counterpart of merged #55299. These are explicit prerequisites, not separate competing fixes. #56438 supplies SP stage boundaries and #56439 supplies cross-stage state transfer; this PR keeps sharing disabled.

Regression and source-check commands

.venv/bin/python -m pytest --noconftest -o addopts= \
  tests/v1/worker/test_gpu_block_table.py -q
DSV41_SPLIT_REPO="$PWD" .venv/bin/python run_cpu_checks.py \
  tests/models/test_deepseek_v41_pipeline.py

The two prefill-workspace CUDA checks use the attached focused harness. The slot guard's recorded 11-case GPU suite is shared with the identical prerequisite repair, not a new complete GPU run of this main tree.

Serving benchmark command

# On the source/configuration identified by the attached run receipt:
.venv/bin/vllm bench serve --backend vllm \
  --base-url http://127.0.0.1:18080 --endpoint /v1/completions --model dsv41 \
  --tokenizer "$MODEL" --tokenizer-mode deepseek_v41 --dataset-name random \
  --random-input-len "$INPUT_LEN" --random-output-len 128 \
  --random-range-ratio 0 --random-prefix-len 0 --num-prompts 16 \
  --max-concurrency 4 --request-rate inf --seed 42 --num-warmups 0 \
  --ready-check-timeout-sec 0 --ignore-eos --disable-tqdm --save-result --save-detailed \
  --percentile-metrics ttft,tpot,itl,e2el --metric-percentiles 10,50,90 \
  --result-dir "$RESULTS" --result-filename "$RESULT_FILE"

INPUT_LEN is 512 or 2048. Run the four warmup requests separately and reset the prefix cache before this timed command. Use the actual port and source/configuration in the attached receipt.

Latest timing records, repair patch, exact configuration and source correspondence. Current rebased branch: 24363d0174165cb8adb0ff4054ba139f39067eb5.

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[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @0z5a.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @0z5a.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork