Enable validated prefix caching and record DGX Spark optimization benchmarks

scripts/prefix-check.py

@@ -0,0 +1,39 @@
+"""Check cached-prefix retrieval at several document positions, including changed suffixes."""
+import json
+import re
+import urllib.request
+from pathlib import Path
+
+base = 'http://127.0.0.1:8000'
+key = Path('/run/secrets/qwen_api_key').read_text().strip()
+headers = {'Authorization': 'Bearer ' + key, 'Content-Type': 'application/json'}
+def request(path, payload=None):
+    req = urllib.request.Request(base+path, headers=headers,
+        data=json.dumps(payload).encode() if payload is not None else None)
+    with urllib.request.urlopen(req, timeout=600) as response:
+        return response.read().decode()
+def hits():
+    return sum(float(line.split()[-1]) for line in request('/metrics').splitlines()
+               if line.startswith('vllm:prefix_cache_hits_total'))
+
+rows = [f'归档记录{i}：此行仅供背景阅读，无有效预算。' for i in range(700)]
+for position, name, amount in [(20,'青松','17391'),(350,'白鹭','28647'),(670,'海棠','39583')]:
+    rows[position] = f'已核定：{name}项目预算为{amount}元。'
+document = '\n'.join(rows)
+before = hits()
+for name, expected in [('青松','17391'),('白鹭','28647'),('海棠','39583'),('青松','17391')]:
+    # Only the question suffix changes. The document prefix is identical.
+    payload = {'model':'qwen3.8-flash-next', 'temperature':0, 'seed':42,
+        'reasoning_effort':'low','max_tokens':512,
+        'messages':[{'role':'user','content':'请根据以下档案回答，忽略无效归档行。\n<档案>\n'+document+'\n</档案>\n'+name+'项目的已核定预算是多少元？只输出数字。'}]}
+    result = json.loads(request('/v1/chat/completions',payload))
+    choice = result['choices'][0]
+    content = choice['message'].get('content') or ''
+    correct = content.strip() == expected and choice['finish_reason']=='stop'
+    print(json.dumps({'project':name,'expected':expected,'content':content,
+        'correct':correct,'usage':result.get('usage')},ensure_ascii=False),flush=True)
+    assert correct, 'Cached prefix answer mismatch'
+delta = hits()-before
+print(json.dumps({'prefix_cache_hits_delta':delta}),flush=True)
+assert delta>0, 'No actual cache hits measured'
+print('PREFIX_CHECK_PASS',flush=True)