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@mikeiovine mikeiovine commented Oct 6, 2025

Description

Fix illegal memory access on MTP 2-model. The extend_ctx mode does not work reliably with MLA (kernel issue). Thankfully, using the same kernels as 1-model will work without any changes.

Test Coverage

Extended existing MTP test to cover the issue.

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Summary by CodeRabbit

  • New Features
    • Broadened “Eagle-style” handling to include MTP Eagle in speculative decoding.
  • Bug Fixes
    • Improved compatibility with TRT-LLM attention backend by disabling chunked-context when using MTP Eagle, preventing incorrect behavior and improving stability.
  • Documentation
    • Clarified speculative execution docstrings related to chunked-context behavior.
  • Tests
    • Updated integration test to run quickstart advanced with three MTP modules, improving coverage for MTP Eagle scenarios.

@mikeiovine mikeiovine requested a review from a team as a code owner October 6, 2025 19:44
@mikeiovine mikeiovine requested review from sunnyqgg and zheyuf and removed request for zheyuf October 6, 2025 19:44
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/bot run

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coderabbitai bot commented Oct 6, 2025

📝 Walkthrough

Walkthrough

Adds a guarded exception in speculative decoding to bypass chunked-context handling for TRTLLM MLA when using MTP_EAGLE mode. Generalizes “Eagle-style” handling in the drafter to include MTP_EAGLE. Updates an integration test to invoke quickstart with 3 MTP modules instead of 1.

Changes

Cohort / File(s) Summary
Speculative decoding control flow
tensorrt_llm/_torch/speculative/interface.py, tensorrt_llm/_torch/speculative/model_drafter.py
interface.py: Adjusted docstring; added guard in SpeculativeDecodingMode.extend_ctx to return False when using TRTLLM attention with MTP_EAGLE (and not one-engine), preserving prior paths otherwise. model_drafter.py: Introduced is_eagle_style to treat Eagle3 and MTP_EAGLE equivalently in TRTLLM branch.
Integration test update
tests/integration/defs/test_e2e.py
In test_ptp_quickstart_advanced_mtp_eagle, changed quickstart invocation to use 3 MTP modules (positional arg “3” instead of “1”); command structure otherwise unchanged.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant Caller
  participant SpecMode as SpeculativeDecodingMode
  participant Attn as AttentionBackend
  participant Drafter as ModelDrafter

  Caller->>SpecMode: extend_ctx(request)
  SpecMode->>Attn: check backend type
  alt use_one_engine() is true
    SpecMode-->>Caller: proceed with existing chunked-context flow
  else If Attn is TrtllmAttention AND mode == MTP_EAGLE
    Note over SpecMode: New guard: disable chunked-context
    SpecMode-->>Caller: return False
  else
    SpecMode-->>Caller: existing behavior (incl. SM checks)
  end

  Caller->>Drafter: prepare_draft(spec_dec_mode, backend)
  Drafter->>Drafter: is_eagle_style = Eagle3 OR MTP_EAGLE
  alt backend is TRTLLM AND is_eagle_style
    Drafter-->>Caller: handle Eagle-style path (broadened)
  else
    Drafter-->>Caller: handle non-Eagle path
  end
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❌ Failed checks (1 warning)
Check name Status Explanation Resolution
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✅ Passed checks (2 passed)
Check name Status Explanation
Title Check ✅ Passed The pull request title follows the required ticket and type format and concisely summarizes the primary change of fixing illegal memory access in the MTP implementation, matching the underlying code updates.
Description Check ✅ Passed The pull request description includes the required Description section with a clear explanation of the issue and solution, a Test Coverage section detailing the added test, and a PR Checklist; these align with the repository’s template and provide sufficient context for reviewers.
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📒 Files selected for processing (3)
  • tensorrt_llm/_torch/speculative/interface.py (1 hunks)
  • tensorrt_llm/_torch/speculative/model_drafter.py (2 hunks)
  • tests/integration/defs/test_e2e.py (1 hunks)
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**/*.{h,hpp,hh,hxx,cpp,cxx,cc,cu,cuh,py}

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  • tensorrt_llm/_torch/speculative/interface.py
  • tests/integration/defs/test_e2e.py
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Files:

  • tensorrt_llm/_torch/speculative/model_drafter.py
  • tensorrt_llm/_torch/speculative/interface.py
  • tests/integration/defs/test_e2e.py
**/*.{cpp,cxx,cc,h,hpp,hh,hxx,cu,cuh,py}

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  • tensorrt_llm/_torch/speculative/interface.py
  • tests/integration/defs/test_e2e.py
🧬 Code graph analysis (3)
tensorrt_llm/_torch/speculative/model_drafter.py (2)
tensorrt_llm/llmapi/llm_args.py (4)
  • spec_dec_mode (411-418)
  • spec_dec_mode (547-552)
  • spec_dec_mode (595-598)
  • spec_dec_mode (708-715)
tensorrt_llm/_torch/speculative/interface.py (2)
  • is_eagle3 (38-39)
  • is_mtp_eagle (35-36)
tensorrt_llm/_torch/speculative/interface.py (1)
tensorrt_llm/_torch/attention_backend/trtllm.py (1)
  • TrtllmAttention (1101-1502)
tests/integration/defs/test_e2e.py (2)
tests/integration/defs/conftest.py (2)
  • llm_venv (700-717)
  • llm_models_root (78-92)
tests/unittest/llmapi/apps/_test_trtllm_serve_multimodal_example.py (1)
  • example_root (56-58)
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PR_Github #20685 [ run ] triggered by Bot

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PR_Github #20685 [ run ] completed with state SUCCESS
/LLM/main/L0_MergeRequest_PR pipeline #15627 completed with status: 'FAILURE'

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Looks good to me.

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/bot run --disable-fail-fast

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PR_Github #20734 [ run ] triggered by Bot

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PR_Github #20734 [ run ] completed with state SUCCESS
/LLM/main/L0_MergeRequest_PR pipeline #15668 completed with status: 'SUCCESS'
Pipeline passed with automatic retried tests. Check the rerun report for details.

@mikeiovine mikeiovine merged commit 7facac0 into NVIDIA:main Oct 7, 2025
7 checks passed
@mikeiovine mikeiovine deleted the fix-mtp branch October 7, 2025 18:03
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3 participants