[https://nvbugs/5782112][fix] Fix hanging issue for MNNVL Allreduce under PP

[hyukn]

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of distributed operations to prevent incompatible configurations when using pipeline parallelism, ensuring correct behavior in parallel processing scenarios.

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Description

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[coderabbitai]

📝 Walkthrough

Walkthrough

Added an early return condition to the is_mnnvl function in the distributed ops module that prevents MNNVL (Megatron NCCL Nvlink) from being used when pipeline parallelism is enabled, introducing a skip path for PP configurations.

Changes

Cohort / File(s)	Summary
Pipeline Parallelism Guard for MNNVL tensorrt_llm/_torch/distributed/ops.py	Added early return condition in is_mnnvl() to skip MNNVL optimization when mapping.has_pp() is true, preventing MNNVL from being applied in pipeline parallelism configurations

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

🚥 Pre-merge checks | ✅ 1 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Description check	⚠️ Warning	PR description is incomplete and largely follows the template structure with no custom content filling the required sections.	Add a detailed description explaining why MNNVL AllReduce should be disabled with PP, list relevant test coverage, and complete all applicable PR checklist items.

✅ Passed checks (1 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly indicates a fix for a hanging issue with MNNVL Allreduce under Pipeline Parallelism (PP), which directly matches the code change that adds an early return when PP is enabled.

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✨ Finishing touches

• 📝 Generate docstrings

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[hyukn]

/bot run --disable-fail-fast

[tensorrt-cicd]

PR_Github #31946 [ run ] triggered by Bot. Commit: 290070c

[timlee0212]

LGTM

[tensorrt-cicd]

PR_Github #31946 [ run ] completed with state SUCCESS. Commit: 290070c
/LLM/main/L0_MergeRequest_PR pipeline #24744 completed with status: 'FAILURE'

⚠️ Action Required:

• Please check the failed tests and fix your PR
• If you cannot view the failures, ask the CI triggerer to share details
• Once fixed, request an NVIDIA team member to trigger CI again

[hyukn]

/bot run --disable-fail-fast

[tensorrt-cicd]

PR_Github #32040 [ run ] triggered by Bot. Commit: 01cc034

[tensorrt-cicd]

PR_Github #32040 [ run ] completed with state SUCCESS. Commit: 01cc034
/LLM/main/L0_MergeRequest_PR pipeline #24831 completed with status: 'FAILURE'

⚠️ Action Required:

• Please check the failed tests and fix your PR
• If you cannot view the failures, ask the CI triggerer to share details
• Once fixed, request an NVIDIA team member to trigger CI again

[hyukn]

/bot run --disable-fail-fast

[tensorrt-cicd]

PR_Github #32086 [ run ] triggered by Bot. Commit: 01cc034

[tensorrt-cicd]

PR_Github #32086 [ run ] completed with state SUCCESS. Commit: 01cc034
/LLM/main/L0_MergeRequest_PR pipeline #24866 completed with status: 'FAILURE'

⚠️ Action Required:

• Please check the failed tests and fix your PR
• If you cannot view the failures, ask the CI triggerer to share details
• Once fixed, request an NVIDIA team member to trigger CI again

[hyukn]

/bot run --disable-fail-fast

[tensorrt-cicd]

PR_Github #32150 [ run ] triggered by Bot. Commit: 01cc034

[tensorrt-cicd]

PR_Github #32150 [ run ] completed with state SUCCESS. Commit: 01cc034
/LLM/main/L0_MergeRequest_PR pipeline #24925 completed with status: 'FAILURE'

⚠️ Action Required:

• Please check the failed tests and fix your PR
• If you cannot view the failures, ask the CI triggerer to share details
• Once fixed, request an NVIDIA team member to trigger CI again

[hyukn]

/bot run --disable-fail-fast

[tensorrt-cicd]

PR_Github #32205 [ run ] triggered by Bot. Commit: 01cc034

[tensorrt-cicd]

PR_Github #32205 [ run ] completed with state SUCCESS. Commit: 01cc034
/LLM/main/L0_MergeRequest_PR pipeline #24969 completed with status: 'SUCCESS'