Gahow Wang
67149130be
- GPU monitor: 5s interval nvidia-smi sampling during benchmarks - A/B test script: clean restart + monitor + benchmark for Combined vs PD-Sep - Fixed proxy: await bootstrap init (race condition), normalized LB scoring - Fixed port conflicts: proxy 9090 to avoid bootstrap 9000 clash Key finding: PD-Sep GPU utilization is 40% of Combined (12.4% vs 30.5%) - Decode GPUs: mean=7.8%, max=47% (memory-bound, compute wasted) - Prefill GPUs: active only 17% of samples (bursty, idle between requests) - Combined: 8 GPUs flexibly used, mean=30.5%, active=64% Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
281 lines
10 KiB
Python
281 lines
10 KiB
Python
"""Unified cache-aware + token-level load-balanced global scheduler.
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Supports two modes:
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--combined URL [URL ...]: PD co-located instances (normal vLLM, no KV transfer)
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--prefill URL BP --decode URL: PD disaggregated instances (Mooncake KV transfer)
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Routing policy (same for both modes):
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score = ongoing_tokens / avg_ongoing - ALPHA * cache_hit_ratio
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Normalized load prevents "rich get richer"; cache bonus gives affinity.
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Session affinity: multi-turn sessions stick to same instance.
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"""
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import argparse
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import asyncio
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import os
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import urllib.parse
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import uuid
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from contextlib import asynccontextmanager
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import httpx
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import uvicorn
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from fastapi import FastAPI, HTTPException, Request
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from fastapi.responses import StreamingResponse
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BLOCK_SIZE = 512
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CACHE_HIT_ALPHA = 1.0 # weight for cache bonus in scoring
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class InstanceState:
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def __init__(self, url: str, bootstrap_port: int | None = None):
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self.url = url
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self.bootstrap_port = bootstrap_port
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self.client = httpx.AsyncClient(
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timeout=None, base_url=url,
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limits=httpx.Limits(max_connections=None, max_keepalive_connections=None),
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)
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self.ongoing_tokens = 0
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self.engine_id: dict[int, str] = {}
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self.dp_size = 1
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self.cached_blocks: set[int] = set()
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def estimate_cache_hit(self, token_ids: list[int] | None) -> int:
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if not token_ids or len(token_ids) < BLOCK_SIZE:
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return 0
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hit = 0
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for i in range(0, len(token_ids) - BLOCK_SIZE + 1, BLOCK_SIZE):
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bh = hash(tuple(token_ids[i:i + BLOCK_SIZE]))
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if bh in self.cached_blocks:
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hit += BLOCK_SIZE
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else:
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break
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return hit
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def record_prefix(self, token_ids: list[int] | None):
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if not token_ids:
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return
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for i in range(0, len(token_ids) - BLOCK_SIZE + 1, BLOCK_SIZE):
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self.cached_blocks.add(hash(tuple(token_ids[i:i + BLOCK_SIZE])))
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if len(self.cached_blocks) > 200000:
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self.cached_blocks = set(list(self.cached_blocks)[-100000:])
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def pick_instance(instances: list[InstanceState], token_ids: list[int] | None,
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session_id: str | None, input_length: int,
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affinity: dict[str, int]) -> tuple[InstanceState, int]:
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"""Normalized load - cache bonus scoring."""
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if session_id and session_id in affinity:
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idx = affinity[session_id]
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if idx < len(instances):
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return instances[idx], idx
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avg_load = max(sum(i.ongoing_tokens for i in instances) / len(instances), 1.0)
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best_idx, best_score = 0, float("inf")
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for i, inst in enumerate(instances):
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cache_hit = inst.estimate_cache_hit(token_ids)
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cache_ratio = cache_hit / input_length if input_length > 0 else 0.0
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score = inst.ongoing_tokens / avg_load - CACHE_HIT_ALPHA * cache_ratio
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if score < best_score:
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best_score = score
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best_idx = i
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if session_id:
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affinity[session_id] = best_idx
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return instances[best_idx], best_idx
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global_args = None
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combined_instances: list[InstanceState] = []
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prefill_instances: list[InstanceState] = []
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decode_instances: list[InstanceState] = []
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session_affinity: dict[str, int] = {}
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is_pd_sep = False
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async def init_prefill_bootstrap(instances: list[InstanceState], ready: asyncio.Event):
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for inst in instances:
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if inst.bootstrap_port is None:
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continue
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while True:
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try:
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await inst.client.get("/health")
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except Exception:
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await asyncio.sleep(1)
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continue
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parsed = urllib.parse.urlparse(str(inst.client.base_url))
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url = f"http://{parsed.hostname}:{inst.bootstrap_port}/query"
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resp = await inst.client.get(url)
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resp.raise_for_status()
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data = resp.json()
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for dp_rank, dp_entry in data.items():
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inst.engine_id[int(dp_rank)] = dp_entry["engine_id"]
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inst.dp_size = len(data)
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print(f"Inited {inst.url} engine_ids={inst.engine_id}")
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break
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ready.set()
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@asynccontextmanager
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async def lifespan(app: FastAPI):
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global is_pd_sep
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app.state.ready = asyncio.Event()
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if global_args.combined:
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is_pd_sep = False
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for url in global_args.combined:
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combined_instances.append(InstanceState(url))
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app.state.ready.set()
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print(f"Combined mode: {len(combined_instances)} instances")
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else:
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is_pd_sep = True
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for url, bp in global_args.prefill:
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prefill_instances.append(InstanceState(url, bp))
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for url in global_args.decode:
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decode_instances.append(InstanceState(url))
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await init_prefill_bootstrap(prefill_instances, app.state.ready)
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print(f"PD-Sep mode: {len(prefill_instances)}P + {len(decode_instances)}D")
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yield
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for inst in combined_instances + prefill_instances + decode_instances:
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await inst.client.aclose()
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app = FastAPI(lifespan=lifespan)
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@app.post("/v1/completions")
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async def handle_completions(request: Request):
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return await _handle(request, "/v1/completions")
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@app.post("/v1/chat/completions")
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async def handle_chat(request: Request):
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return await _handle(request, "/v1/chat/completions")
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async def _handle(request: Request, api: str):
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if not app.state.ready.is_set():
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raise HTTPException(status_code=503, detail="Service Unavailable")
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req_data = await request.json()
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request_id = str(uuid.uuid4())
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prompt = req_data.get("prompt")
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token_ids = prompt if isinstance(prompt, list) else None
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input_length = len(token_ids) if token_ids else 0
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session_id = request.headers.get("X-Session-Id")
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headers = {"X-Request-Id": request_id}
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api_key = os.environ.get("OPENAI_API_KEY")
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if api_key:
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headers["Authorization"] = f"Bearer {api_key}"
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if is_pd_sep:
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return await _handle_pd_sep(api, req_data, request_id, token_ids,
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input_length, session_id, headers)
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else:
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return await _handle_combined(api, req_data, token_ids,
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input_length, session_id, headers)
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async def _handle_combined(api, req_data, token_ids, input_length, session_id, headers):
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"""Combined mode: route to best instance, send normal request."""
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inst, idx = pick_instance(combined_instances, token_ids, session_id,
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input_length, session_affinity)
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inst.ongoing_tokens += input_length
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async def generate():
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try:
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async with inst.client.stream("POST", api, json=req_data, headers=headers) as resp:
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resp.raise_for_status()
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async for chunk in resp.aiter_bytes():
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yield chunk
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inst.record_prefix(token_ids)
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finally:
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inst.ongoing_tokens -= input_length
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return StreamingResponse(generate(), media_type="text/event-stream")
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async def _handle_pd_sep(api, req_data, request_id, token_ids, input_length,
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session_id, headers):
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"""PD-Sep mode: await prefill, then stream decode."""
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p_inst, _ = pick_instance(prefill_instances, token_ids, session_id,
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input_length, session_affinity)
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d_inst = min(decode_instances, key=lambda x: x.ongoing_tokens)
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# Await prefill
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p_inst.ongoing_tokens += input_length
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try:
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prefill_data = req_data.copy()
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prefill_data["kv_transfer_params"] = {
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"do_remote_decode": True, "do_remote_prefill": False,
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"transfer_id": f"xfer-{request_id}",
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}
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prefill_data["stream"] = False
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prefill_data["max_tokens"] = 1
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prefill_data.pop("max_completion_tokens", None)
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prefill_data.pop("stream_options", None)
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p_headers = {**headers, "X-data-parallel-rank": "0"}
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resp = await p_inst.client.post(api, json=prefill_data, headers=p_headers)
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resp.raise_for_status()
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await resp.aclose()
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p_inst.record_prefix(token_ids)
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except Exception as e:
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raise HTTPException(status_code=502, detail=f"Prefill failed: {e}")
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finally:
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p_inst.ongoing_tokens -= input_length
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# Stream decode
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d_inst.ongoing_tokens += input_length
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parsed = urllib.parse.urlparse(str(p_inst.client.base_url))
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bootstrap_addr = f"http://{parsed.hostname}:{p_inst.bootstrap_port}"
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decode_data = req_data.copy()
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decode_data["kv_transfer_params"] = {
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"do_remote_decode": False, "do_remote_prefill": True,
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"remote_bootstrap_addr": bootstrap_addr,
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"remote_engine_id": p_inst.engine_id.get(0, ""),
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"transfer_id": f"xfer-{request_id}",
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}
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async def generate():
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try:
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async with d_inst.client.stream("POST", api, json=decode_data, headers=headers) as resp:
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resp.raise_for_status()
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async for chunk in resp.aiter_bytes():
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yield chunk
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finally:
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d_inst.ongoing_tokens -= input_length
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return StreamingResponse(generate(), media_type="application/json")
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def parse_args():
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p = argparse.ArgumentParser(description="Unified cache-aware global scheduler")
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p.add_argument("--port", type=int, default=8000)
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p.add_argument("--host", type=str, default="0.0.0.0")
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p.add_argument("--combined", nargs="+", help="Combined mode: list of instance URLs")
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p.add_argument("--prefill", nargs="+", action="append", dest="prefill_raw",
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help="PD-Sep prefill: URL [bootstrap_port]")
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p.add_argument("--decode", nargs=1, action="append", dest="decode_raw",
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help="PD-Sep decode: URL")
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args = p.parse_args()
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args.prefill = []
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if args.prefill_raw:
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for entry in args.prefill_raw:
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url = entry[0]
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bp = int(entry[1]) if len(entry) > 1 and entry[1].lower() != "none" else None
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args.prefill.append((url, bp))
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args.decode = [e[0] for e in (args.decode_raw or [])]
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if not args.combined and not args.prefill:
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p.error("Must specify either --combined or --prefill/--decode")
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return args
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if __name__ == "__main__":
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global_args = parse_args()
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uvicorn.run(app, host=global_args.host, port=global_args.port)
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