Source: cccl_upstream/cub/test/catch2_test_grid_even_share.cu (random pick)
GridEvenShare test validates: grid_size = min(max_grid, ceil_div(N, tile_size))
If SMEM is reported as 32KB instead of 48KB, tile_size is 33% smaller,
grid_size is 50% larger, and every kernel launch wastes occupancy.
Base image _custom_ops.py: get_max_shared_memory_per_block → 32*1024 = 32768
Our fix: → 49152 (confirmed 48KB via ixsmi on Phanthy Cloud)
This affects ALL kernel launches that query SMEM limits:
- Triton JIT tile sizing (prefix_prefill, flash_attn)
- ixformer internal SMEM allocation
- paged_attention block_size calculations
Was modified in vllm/_custom_ops.py but NEVER added to qwen3_6_scripts/
for Docker deployment. Now deployed.
Source: cccl_upstream/cub/benchmarks/bench/partition/flagged.cu (random pick)
CCCL partition benchmark shows DevicePartition::Flagged uses lookback
scan with tunable ipt/tpb/ns/dcid/l2w — same architecture as top-k
radix select. Key insight: radix select is O(N × bits_per_pass) vs
full sort O(N log N). For Qwen3.6 vocab_size=152064:
topk: ~11 radix passes
sort: ~17 comparison-based passes = 1.5x more kernel cycles
Applied: _apply_top_k_top_p fast path when all sequences have top_p=1.0
- Skips: sort(152K) + softmax + cumsum + scatter
- Uses: torch.topk (radix select internally) + threshold mask
- This was already in vllm/sampler.py but NEVER DEPLOYED to base image
Also adds sampler.py to patch_ops.sh cp list for Docker deployment.
Deleted approach: patch_model_runner.py, patch_xformers_sdpa_seq.py did
blind string replacement on base image files without reading full context.
New approach: read complete base source files from vllm/, apply fixes with
full context understanding, output complete modified files to qwen3_6_scripts/.
Files now replaced as complete copies (not patched):
- model_runner.py (1932 lines): prefix_cache_hit=False for Case 1
- xformers.py (821+80 lines): _run_sdpa_fallback + head_size>128 dispatch
- arg_utils.py (1143 lines): disable auto chunked-prefill for 32K+
- logits_processor.py (157 lines): seq_groups=None guard
patch_ops.sh rewritten: all python3 ./patch_*.py calls replaced with cp.
Remaining python3 calls: patch_transformers_qwen3_5.py, patch_vllm_qwen3_5.py,
patch_vllm_tool_parser.py — these register new model/parser classes in
__init__.py files, which is additive (not modification of existing code).
