Add qwen235b thinking decode tuning note

docs/qwen235b-thinking-decode/README.md

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+# qwen235b-thinking-decode
+
+qwen3-235b-a22b `thinking` trace, `decode_only` mode, internal vLLM (`/usr/local/bin/vllm`), SLO: `p95-equivalent pass target 95%`, `TPOT <= 40ms`, `TTFT` not enforced.
+
+## Run assets
+
+- Study root: `/home/admin/cpfs/wjh/aituner/aituner/.aituner-decode/dash0-qwen235b-decode-thinking-run5-tpot40-topology`
+- State: `/home/admin/cpfs/wjh/aituner/aituner/.aituner-decode/dash0-qwen235b-decode-thinking-run5-tpot40-topology/state.json`
+- Log: `/home/admin/cpfs/wjh/aituner/aituner/logs/dash0_qwen235b_decode_thinking_run5_tpot40_topology.log`
+- Spec: `/home/admin/cpfs/wjh/aituner/aituner/.aituner-decode/specs/dash0_qwen235b_decode_thinking_run5_tpot40_topology.json`
+
+## Best result
+
+- Best trial: `trial-0009`
+- Best config:
+  - `tensor-parallel-size=2`
+  - `data-parallel-size=4`
+  - `expert-parallel-size=8`
+  - `max-num-seqs=128`
+  - `max-num-batched-tokens=256`
+- Best `sampling_u`: `0.013218402863`
+- Best request rate: `0.2816666666666667 req/s`
+- Best pass rate: `0.9704142011834319`
+
+Compared with baseline:
+
+- `trial-0001`: `0.12666666666666668 req/s`
+- `trial-0009`: `0.2816666666666667 req/s`
+- Throughput gain: `2.22x`
+
+Best-point latency:
+
+- `TPOT mean/p50/p90/p95/p99 = 27.49 / 26.50 / 38.73 / 39.57 / 40.73 ms`
+- `TTFT mean/p50/p90/p95/p99 = 216.33 / 199.62 / 298.56 / 308.91 / 317.00 ms`
+
+## 12-trial summary
+
+| Trial | Proposed config delta | Result |
+| --- | --- | --- |
+| `trial-0001` | baseline | `0.1267 req/s`, feasible |
+| `trial-0002` | `TP=2, DP=4` | `0.2450 req/s`, feasible |
+| `trial-0003` | `TP=1, DP=8, EP=8` | infeasible |
+| `trial-0004` | `TP=2, DP=4, EP=4` | launch fail |
+| `trial-0005` | `gpu-memory-utilization=0.8`, `max-num-seqs=256` | infeasible |
+| `trial-0006` | `max-num-seqs=128` | infeasible |
+| `trial-0007` | `block-size=128` | infeasible |
+| `trial-0008` | `max-num-batched-tokens=384` | infeasible |
+| `trial-0009` | `TP=2, DP=4, EP=8`, `max-num-seqs=128`, `max-num-batched-tokens=256` | `0.2817 req/s`, feasible, best |
+| `trial-0010` | `trial-0009 + block-size=128` | infeasible |
+| `trial-0011` | `TP=1, DP=8, EP=8`, `max-num-seqs=128`, `max-num-batched-tokens=256` | infeasible |
+| `trial-0012` | `TP=2, DP=4, EP=8`, `max-num-seqs=96`, `max-num-batched-tokens=192` | infeasible |
+
+## Key insights
+
+- Removing `VLLM_USE_FLASHINFER_SAMPLER`, `CUDA_DEVICE_MAX_CONNECTIONS`, `VLLM_ENABLE_TBO_OPT` from tunable space did not block progress; the win came from `parallel space`.
+- The first strong improvement was topology: `TP4/DP2/EP8 -> TP2/DP4/EP8`.
+- `TP1/DP8/EP8` launched, but did not beat `TP2/DP4/EP8`.
+- `EP4` under `TP2/DP4` failed at launch and should be treated as negative evidence for this stack.
+- After topology settled at `TP2/DP4/EP8`, the useful runtime refinement was tighter decode batching: `max-num-seqs=128`, `max-num-batched-tokens=256`.
+
+## Current recommendation
+
+Use the `trial-0009` shape as the default decode-only serving config for this workload:
+
+- `tensor-parallel-size=2`
+- `data-parallel-size=4`
+- `expert-parallel-size=8`
+- `max-num-seqs=128`
+- `max-num-batched-tokens=256`