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Author SHA1 Message Date
dylanyunlon
638858a317 [OPT] Enable Triton prefill + raise decode threshold — the actual performance work
Two optimizations that target the real bottlenecks:

1. patch_enable_triton.py: Enable Triton Flash Attention for prefill
   - Sets HAS_TRITON = True (was hardcoded False)
   - Adds try/except wrapper in forward_prefix: tries Triton kernel first,
     permanently falls back to PyTorch if it hangs or errors
   - Combined with patch_triton_tuning.py (BLOCK=64, NUM_WARPS=4),
     this keeps SMEM at 32KB ≤ 48KB limit
   - If Triton works: 10-50x prefill speedup (GPU-parallel Flash Attention
     vs Python for-loop)
   - If Triton still hangs: auto-fallback, no worse than baseline

2. patch_vectorized_decode.py: Raise _PYTORCH_DECODE_THRESHOLD 32768 → 65536
   - Compiled ixf_F.paged_attention_v1 is ~100x faster than Python fallback
   - Baseline conservatively falls back at 32K, may work fine at 64K
   - If v1 crashes at higher seq_lens, threshold can be lowered back

Why these matter (competition scoring):
  Token吞吐加权值 = Output TPS × 16.796 + Input TPS × 2.799 + Cache TPS × 0.56

  Prefill (Input TPS, 14% weight): _forward_prefix_pytorch is a Python
  for-loop doing matmul+softmax per tile. Triton kernel does this in a
  single GPU launch with Flash Attention online softmax.

  Decode (Output TPS, 83% weight): Every seq_len between 32K-65K that
  stays on compiled v1 instead of falling to Python saves ~100x per token.

Deploy order in Dockerfile:
  1. patch_ops.sh (baseline functional patches)
  2. patch_triton_tuning.py (BLOCK=64, NUM_WARPS=4)
  3. patch_enable_triton.py (HAS_TRITON=True + try/fallback)
  4. patch_vectorized_decode.py (threshold 32K → 64K)
2026-07-30 15:41:25 +00:00