PD-sep server-side profiling: vLLM patches + per-request breakdown

Instrumentation patches (microbench/patches/):
  - pd_profile.py: shared event emitter (VLLM_PD_PROFILE_LOG env var)
  - apply_patches.py: idempotent patch installer for mooncake_connector.py
    and scheduler.py, marks insertions with # PD_PROFILE_PATCH
  - analyze_events.py: joins per-process JSONL event logs by transfer_id
    into per-request phase durations

Seven events captured per request:
  D_get_num_matched → P_zmq_received → P_prefill_done →
  P_rdma_start → P_rdma_end → D_recv_complete → D_request_promoted

Driver fix (microbench/lifecycle/driver.py):
  seed_prefix_cache now sends via the proxy URL so P and D both cache
  the seeded prefix with matching block hashes. Previously seeding D
  directly produced different block hashes than the proxy-routed
  measurement requests, making incremental transfer impossible.

Real breakdown (fig_breakdown_real.png, server_breakdown.csv, n=93):
  prefill_compute  620 ms median (95% of overhead)
  rdma_transfer     42 ms median (~71 Gbps effective)
  other overhead    10 ms median (dispatch + params + signal + promote)

Mooncake transfer is NOT the bottleneck. Even with bulk RDMA the
transfer cost is <10% of prefill cost for Qwen3-30B-A3B on H20.

microbench/patches/pd_profile.py

@@ -0,0 +1,57 @@
+"""
+PD-Sep Lifecycle Profiler — patch for mooncake_connector.py + scheduler.py
+
+Activated by env var: VLLM_PD_PROFILE_LOG=/path/to/events.jsonl
+
+Each line is one event:
+  {"t_ns": <perf_counter_ns>, "event": "<name>", "req_id": "<id>",
+   "transfer_id": "<id>", "role": "<kv_producer|kv_consumer>",
+   "data": {...event-specific fields...}}
+
+This module is imported by the patched mooncake_connector.py and scheduler.py
+to centralize event emission.
+"""
+
+import os
+import json
+import time
+import threading
+from typing import Any
+
+_LOG_FILE = os.environ.get("VLLM_PD_PROFILE_LOG", "")
+_LOCK = threading.Lock()
+_HANDLE = None
+_ENABLED = bool(_LOG_FILE)
+
+
+def _get_handle():
+    global _HANDLE
+    if _HANDLE is None and _ENABLED:
+        _HANDLE = open(_LOG_FILE, "a", buffering=1)  # line-buffered
+    return _HANDLE
+
+
+def emit(event: str, req_id: str = "", transfer_id: str = "",
+         role: str = "", **data: Any) -> None:
+    """Record a profile event. No-op if VLLM_PD_PROFILE_LOG is not set."""
+    if not _ENABLED:
+        return
+    record = {
+        "t_ns": time.perf_counter_ns(),
+        "event": event,
+        "req_id": str(req_id),
+        "transfer_id": str(transfer_id),
+        "role": role,
+        "data": data,
+    }
+    try:
+        h = _get_handle()
+        if h:
+            with _LOCK:
+                h.write(json.dumps(record, default=str) + "\n")
+    except Exception:
+        pass  # never let profiling break vLLM
+
+
+def enabled() -> bool:
+    return _ENABLED