Hybrid EP：Support configurable IB Traffic Class via HYBRID_EP_IB_TC env var

[kzlxd]

Summary

This PR adds support for configuring the IB Traffic Class (TC) used in RDMA QP setup via an environment variable, replacing the previously hardcoded value.

• Add HYBRID_EP_IB_TC for runtime configuration
• Remove hardcoded DEF_IB_TC = 0
• Introduce get_ib_tc_value() with range validation (0–255)
• Fix DOCA compilation issue by adding missing headers

This change was motivated by observed performance anomalies when using TC=0 (e.g., ~46 GB/s in 2-node dispatch scenarios), which revealed that the TC value was hardcoded.

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Changes

IB TC Configuration

csrc/hybrid_ep/buffer/internode_doca.cuh

• Remove DEF_IB_TC
• Declare get_ib_tc_value()

csrc/hybrid_ep/buffer/internode_doca.cu

• Implement get_ib_tc_value():

  • Read HYBRID_EP_IB_TC from environment
  • Validate range [0, 255]
  • Fall back to 0 if invalid (with warning)

• Replace all usages of DEF_IB_TC with get_ib_tc_value()

• Add missing includes:

  #include <torch/extension.h>
  #include

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Usage

# Optional: set IB Traffic Class (default = 0)
export HYBRID_EP_IB_TC=162

python -u tests/test_hybrid_ep.py --num-processes 8

• Values outside [0, 255] will:
  • Trigger a warning
  • Fall back to 0

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Performance Impact

• Before (TC=0): ~46 GB/s (2-node dispatch)
• After (e.g., TC=162): significantly improved throughput

Note: exact gains depend on network configuration and topology.

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Notes

• Aligns with NVSHMEM-style runtime configurability
• Helps avoid performance issues on certain platforms (e.g., B300 with TC=0)
• Backward compatible (default remains TC=0)