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Base runtime (dev20073+g8e685d198, not on upstream main) ships customized mamba_hybrid.py/scheduler.py, so the verbatim PR diffs failed to apply. Re-expressed the semantic fixes against the base's real lines (dumped via flashnext-base-dump), py_compiled and dry-run --fuzz=0 clean: vllm-project#53798 full; vllm-project#54076 hunks 1+2 (block-size source). vllm-project#54076 hunk 3 omitted (base has no internal-checkpoint path). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Measured on GB10 with MTP n=5: this patch alone takes healthy-acceptance turns from 44 % (12 starts) to 14/16; both PRs together 63/72 over 7 starts. Numbers and method in #53142 (comment). |
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Correction: the acceptance percentages I quoted were a benchmark artifact ( |
…ock units The seed divided by cache_config.block_size; once page unification no longer keeps scheduler and mamba block widths equal, a resumed request seeds its precopy source to a garbage block-table column (silent neighbour-state corruption at moderate lengths, CUDA illegal access at ~100k+). Use the mamba spec's block width, assert it is resolved before any computed-token resume, and keep the static helper for the imported regression tests (7 passed; tests landed with aa774d8).
AndreasKaratzas
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LGTM -- Probably somebody else should take a look into this though as well.
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not sure if test file is needed here
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✅ @ptorsten, CI is now available for this PR.
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ptorsten
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No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info⚙️ Run configurationConfiguration used: Repository UI Review profile: CHILL Plan: Team Run ID: 📒 Files selected for processing (6)
Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review. 📝 SummarySummary by CodeRabbit
WalkthroughChangesThe model runner now passes KV cache configuration binding
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: ⚪ Minimal · up to This change corrects resumed align-mode Mamba request state seeding when Mamba blocks differ from scheduler blocks, preventing incorrect table indexing or memory access. The updated behavior is covered by targeted tests, with no remaining merge-blocking risk identified. Sequence Diagram(s)sequenceDiagram
participant GPUModelRunner
participant MambaHybridModelState
participant KVCacheConfig
GPUModelRunner->>MambaHybridModelState: set_kv_cache_config(KVCacheConfig)
MambaHybridModelState->>KVCacheConfig: read Mamba group metadata
MambaHybridModelState->>MambaHybridModelState: seed request state index from Mamba block size
Suggested reviewers: 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out. Comment |
MambaHybridModelState.add_request seeds a resumed request's running state block with (num_computed_tokens - 1) // cache_config.block_size. The align block table is laid out in Mamba blocks (MambaSpec.block_size), which the engine core can scale past the scheduler block during page unification, and the precopy kernel indexes the table in those units. The seed then lands in another row's column, or past the table at depth (illegal memory access). The V1 path in mamba_utils already divides by mamba_spec.block_size. The model state only sees the Mamba spec on the first real batch, after add_request, so it cannot look the size up lazily. Give it the KV cache config when the runner initializes the KV cache (ModelState.set_kv_cache_config, no-op by default), resolve the Mamba groups there, and seed with MambaSpec.block_size. Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com> Signed-off-by: Patrik Torstensson <patrik.torstensson@gmail.com>
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Closing out the correction I promised here on 2026-09-03, and the answer is that I am withdrawing the What I posted on 09-02 — "this patch alone takes healthy-acceptance turns from 44 % to 15/16" — used Why I am not supplying a replacement effect size. I re-ran the grid EOS-correctly and have a clean What is unaffected, and is why I still think this PR is right: the defect is a code fact, not a Offer. This PR has been blocked on conflicts twice in three days with no reviewer, and I would rather Apologies for the six-day gap on a correction I said would follow immediately. AI assistance was used in preparing this comment; the measurements are ours and were reviewed before posting. |
MaCoredroid
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Reviewed af5357c2b locally; traced the invariant through the production
call paths rather than the description.
Invariant. MambaHybridModelState._mamba_state_idx_gpu indexes the
align block table in MambaSpec.block_size units. preprocess_state
advances it using MAMBA_BLOCK_SIZE=mamba_spec.block_size, and the pre-copy
kernel uses it as a block-table column. On main at
8359e15aae32dee9dc1f259a9b2574fb72b5507e, add_request instead seeds it
with (num_computed_tokens - 1) // cache_config.block_size. When these
block sizes differ, that seed can select the wrong column or exceed the
table. V1 already uses mamba_spec.block_size for prev_state_idx; this
PR makes MRV2 use the same unit.
Binding order. GPUModelRunner.initialize_kv_cache calls
set_kv_cache_config after init_attn_backend and before
get_additional_cg_support; requests are added after KV initialization.
All three production callers of _get_mamba_group_info() (add_request,
preprocess_state, prepare_attn) are guarded by align mode, matching the
early return in set_kv_cache_config for non-align modes. These paths
therefore do not reach the new bound-spec assertion in none/all modes.
The existing assertion that Mamba groups share cache scheduling parameters
now runs during KV initialization rather than on the first batch.
Pre-existing semantics preserved. A fresh request (num_computed_tokens == 0) still seeds -1; that is unchanged from main and is the value the
pre-copy kernel fast-exits on (src_col < 0). _ensure_align_ctx still
resolves copy funcs from kv_cache_config independently; unaffected.
Test. test_add_request_seeds_state_idx_in_mamba_blocks constructs the
state with object.__new__, binds an 880-token Mamba block beside a
16-token scheduler block, and checks (107_360 - 1) // 880 == 121. The old
denominator would produce 6709. This CPU test covers the seed calculation;
it does not execute the pre-copy kernel or reproduce the illegal memory
access. The two test_mamba_utils.py edits exercise the new binding step
before the no-argument lookup.
Verification (local).
git merge-tree --write-tree 8359e15aae32dee9dc1f259a9b2574fb72b5507e af5357c2b90b37bd2033578bbc97d0ddfa6cc69f
completed without conflicts. That main snapshot has 52 commits absent
from the PR head. The test result below is for the PR head, not the
merged tree.pytest tests/v1/worker/test_mamba_hybrid_model_state.py tests/v1/worker/test_mamba_utils.py tests/v1/worker/test_gpu_model_runner_v2.py
ataf5357c2bon a GB10 (sm_121, CUDA tests included): 56 passed in 9.2 s.
Scope note, not a blocker. This fixes the worker-side seed. The
scheduler-side chunk grid for unequal geometries is #54076's concern; the
two are independent layers and this PR does not depend on it.
Adapt vLLM vllm-project#53945/vllm-project#54713 replay retention, vllm-project#54076 state-grid selection and vllm-project#53798 worker resume geometry. Preserve other hybrid models TP>2 workaround. Qualify identical and extended conversations on four V620s, and include a bounded HTTP reproducer. Co-authored-by: tobymao <toby.mao@gmail.com> Co-authored-by: Patrik Torstensson <patrik.torstensson@gmail.com> Co-authored-by: wickist <261605936+wickist@users.noreply.github.com> Co-authored-by: wzhao18 <wzhao18.sz@gmail.com> Co-authored-by: Adam Shaver <ashaver@nvidia.com> Co-authored-by: Codex <noreply@openai.com> Signed-off-by: George Muravei-Alkhavoi <georgezagraid@gmail.com>
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Following up on the review: here is a two-commit, test-only addition atop Model-free conv/SSM pools with synthetic padding exercise real This covers worker restore fidelity, not scheduler publication or model outputs. If useful, cherry-pick |
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This pull request has merge conflicts that must be resolved before it can be |
4 participants
Purpose
MambaHybridModelState.add_requestseeds a resumed request's running state block with(num_computed_tokens - 1) // cache_config.block_size. The align block table is laid out in Mamba blocks,MambaSpec.block_size, which the engine core can scale past the scheduler block when it unifies page sizes (unify_kv_cache_spec_page_size,get_kv_cache_groups), and the precopy kernel indexes the table in those units. The seed then lands in another row's column, or past the table at depth (illegal memory access inprecopy_mamba_align_fused_kernel). The V1 path inmamba_utils.pyalready divides bymamba_spec.block_size.The model state only sees the Mamba spec on the first real batch, after
add_request, so it cannot look the size up lazily. Give it the KV cache config when the runner initializes the KV cache (ModelState.set_kv_cache_config, no-op by default), resolve the Mamba groups there, and seed withMambaSpec.block_size.Replaces the first revision, which cached the size lazily with a scheduler-block fallback. No open PR touches align-mode seeding.
Test
pytest tests/v1/worker/test_mamba_hybrid_model_state.py tests/v1/worker/test_mamba_utils.py tests/v1/worker/test_gpu_model_runner_v2.py- 53 passed. The new case runsadd_requestwith an 880-token Mamba block beside a 16-token scheduler block; it is the guard for the crash, since the two sizes coincide on today'smainfor the models below.2x DGX Spark, TP=2, Qwen3.8-27B-NVFP4 hybrid,
--prefix-cache-retention-interval, 133k-token document: fresh, identical resubmit (prefix hit, resumed with computed tokens), new question. Onmainand onmain+ this commit the resume completes with 132,800 prefix-hit tokens and the resumed answer equals the fresh one at T=0; no regression. On a lineage with unified KV pages (Mamba block 1568) the same holds with a DFlash2 drafter, 12/12 on the tool-calling suite, unchanged from the previous revision. The illegal memory access itself reproduced on an earlier geometry of that lineage where the Mamba block differed from the attention block.AI assistance was used; every line reviewed and the unit tests above run by me.