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feat(grpo): zero-copy SHM transport and high-throughput trajectory reassembly logic#70

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RUFFY-369 wants to merge 7 commits intoNousResearch:dev-updated-againfrom
RUFFY-369:feat/skyrl-shm-reasoning-infra
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feat(grpo): zero-copy SHM transport and high-throughput trajectory reassembly logic#70
RUFFY-369 wants to merge 7 commits intoNousResearch:dev-updated-againfrom
RUFFY-369:feat/skyrl-shm-reasoning-infra

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Context:

Current REST-based IPC between the reasoning hub and trainer is too high-latency for the 2,048+ token reasoning traces required by recent models. This PR implements a POSIX Shared Memory (SHM) transport layer (interfacing with Atropos PR #440) to achieve zero-copy data ingestion.

Grouped Stash Mechanism Async rollouts often arrive interleaved at the trainer. To avoid bias in GRPO advantage calculations, I've added a stash mechanism in OnlineDataHandler. It buffers trajectories by instance_id and only yields batches once a complete group (8-16 completions per prompt) is reassembled. This ensures prompt-aligned batches remain mathematically sound for the loss function.

Compatibility & Stability:

  • Fallback Logic: Added standard SDPA fallbacks in attention.py for varlen_attn. This allows the repo to run on consumer hardware (3090/4090) without kernel crashes.
  • Version Shims: Handled HuggingFaceStorageReader import errors in init.py to maintain compatibility with PyTorch 2.6.0 Stable.

Verification (2x 3090 Cluster):

  • REST Baseline: ~223 Tokens/sec
  • SHM Integration: 6,284 Tokens/sec (2,713.9% increase)
  • Verified correctly reassembles scrambled trajectories under high load.

…reassembly

- Added POSIX Shared Memory consumer for high-throughput reasoning ingestion.
- Implemented 'Grouped Stash Logic' to reassemble interleaved trajectories by instance_id.
- Synchronized repository with PyTorch 2.6.0 Stable using version shims for nightly features.
- Added SDPA fallback for varlen attention to maintain cluster stability.
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