[Feat] DiffusionEngine Support async batch infer (#2729)

Signed-off-by: Semmer <semmer@live.cn>
Signed-off-by: jader <yjader@foxmail.com>
Signed-off-by: asukaqaq-s <1311722138@qq.com>
Co-authored-by: asukaqaq-s <1311722138@qq.com>
Co-authored-by: jader <yjader@foxmail.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>
Co-authored-by: Gao Han <hgaoaf@connect.ust.hk>

benchmarks/diffusion/README.md

@@ -130,9 +130,21 @@ Warmup flags:
 
 - `--warmup-requests`: Number of warmup requests.
 - `--warmup-num-inference-steps`: Steps used during warmup.
+- `--warmup-concurrency`: Maximum concurrent warmup requests. Use this to warm
+  the same batch shape as the measured run instead of warming only batch=`1`.
 - For `--task t2v`: warmup requests are forced to use `num_frames=1` to make warmup faster and less noisy.
 
 Traffic / concurrency flags:
 
 - `--request-rate`: Target request rate (requests/second). If set to `inf`, the script sends all requests immediately.
 - `--max-concurrency`: Max number of in-flight requests (default: `1`). This can hard-cap the achieved QPS: if it is too small, requests will queue behind the semaphore, and both achieved throughput and observed SLO attainment can be skewed.
+
+### Batched warmup note
+
+For batched serving runs, warm the same in-flight shape you plan to measure.
+For example, a run with `--max-concurrency 8` should usually also use
+`--warmup-requests 8 --warmup-concurrency 8`; otherwise the first measured
+batch may still pay compile or CUDA-graph capture cost.
+
+For a Qwen-Image continuous-batching replay example, see
+[`performance_dashboard/qwen_image_serving_performance.md`](./performance_dashboard/qwen_image_serving_performance.md).

benchmarks/diffusion/diffusion_benchmark_serving.py

@@ -751,6 +751,52 @@ async def iter_requests(
         yield req
 
 
+def _make_warmup_request(
+    requests_list: list[RequestFuncInput],
+    index: int,
+    args,
+) -> RequestFuncInput:
+    warm_req = requests_list[index % len(requests_list)]
+    if args.warmup_num_inference_steps is not None:
+        warm_req = replace(
+            warm_req,
+            num_inference_steps=args.warmup_num_inference_steps,
+        )
+    if args.task == "t2v":
+        warm_req = replace(warm_req, num_frames=1)
+    return warm_req
+
+
+async def _run_warmups(
+    requests_list: list[RequestFuncInput],
+    args,
+    session: aiohttp.ClientSession,
+    request_func,
+) -> list[tuple[RequestFuncInput, RequestFuncOutput]]:
+    if not args.warmup_requests or not requests_list:
+        return []
+
+    warmup_requests = [_make_warmup_request(requests_list, i, args) for i in range(args.warmup_requests)]
+    warmup_concurrency = min(int(args.warmup_concurrency), len(warmup_requests))
+    warmup_semaphore = asyncio.Semaphore(warmup_concurrency)
+
+    print(
+        f"Running {len(warmup_requests)} warmup request(s) "
+        f"with num_inference_steps={args.warmup_num_inference_steps} "
+        f"and warmup_concurrency={warmup_concurrency}..."
+    )
+
+    async def limited_warmup_request_func(
+        req: RequestFuncInput,
+    ) -> RequestFuncOutput:
+        async with warmup_semaphore:
+            return await request_func(req, session, None)
+
+    warmup_tasks = [asyncio.create_task(limited_warmup_request_func(req)) for req in warmup_requests]
+    warmup_outputs = await asyncio.gather(*warmup_tasks)
+    return list(zip(warmup_requests, warmup_outputs))
+
+
 def calculate_metrics(
     outputs: list[RequestFuncOutput],
     total_duration: float,
@@ -900,23 +946,12 @@ async def benchmark(args):
     pbar = tqdm(total=len(requests_list), disable=args.disable_tqdm)
 
     async with aiohttp.ClientSession() as session:
-        warmup_pairs: list[tuple[RequestFuncInput, RequestFuncOutput]] = []
-        if args.warmup_requests and requests_list:
-            print(
-                f"Running {args.warmup_requests} warmup request(s) \
-                with num_inference_steps={args.warmup_num_inference_steps}..."
-            )
-            for i in range(args.warmup_requests):
-                warm_req = requests_list[i % len(requests_list)]
-                if args.warmup_num_inference_steps is not None:
-                    warm_req = replace(
-                        warm_req,
-                        num_inference_steps=args.warmup_num_inference_steps,
-                    )
-                if args.task == "t2v":
-                    warm_req = replace(warm_req, num_frames=1)
-                warm_out = await limited_request_func(warm_req, session, None)
-                warmup_pairs.append((warm_req, warm_out))
+        warmup_pairs = await _run_warmups(
+            requests_list=requests_list,
+            args=args,
+            session=session,
+            request_func=request_func,
+        )
 
         if args.slo:
             # Prefer trace-provided per-request slo_ms. Only populate when missing.
@@ -1072,6 +1107,13 @@ if __name__ == "__main__":
         default=1,
         help="num_inference_steps used for warmup requests.",
     )
+    parser.add_argument(
+        "--warmup-concurrency",
+        type=int,
+        default=1,
+        help="Maximum number of warmup requests to run concurrently. "
+        "Set this to match the real batch shape when warming up torch.compile or CUDA graphs.",
+    )
     parser.add_argument("--width", type=int, default=None, help="Image/Video width.")
     parser.add_argument("--height", type=int, default=None, help="Image/Video height.")
     parser.add_argument("--num-frames", type=int, default=None, help="Number of frames (for video).")
@@ -1135,5 +1177,4 @@ if __name__ == "__main__":
     )
 
     args = parser.parse_args()
-
     asyncio.run(benchmark(args))

benchmarks/diffusion/performance_dashboard/qwen_image_serving_performance.md

@@ -33,6 +33,12 @@ vllm serve Qwen/Qwen-Image --omni \
     --port 8091
 ```
 
+To replay step-wise continuous batching, compare
+`vllm serve Qwen/Qwen-Image --omni --port 8089 --step-execution --max-num-seqs 1`
+against the same command with `--max-num-seqs 8`. `--step-execution` is the
+feature gate, and increasing `--max-num-seqs` above `1` lets the scheduler
+keep more compatible requests active at once.
+
 ## 3.2 Key Parameters
 
 | Parameter             | Description              |
@@ -70,6 +76,7 @@ python benchmarks/diffusion/diffusion_benchmark_serving.py \
 | `--task`               | Task type (e.g., `t2i`)           |
 | `--num-prompts`        | Total number of requests          |
 | `--max-concurrency`    | Client-side concurrency           |
+| `--warmup-concurrency` | Warmup concurrency for batch-shape prewarming |
 | `--random-request-config`| JSON string defining random request |
 
 ---
@@ -133,6 +140,12 @@ python benchmarks/diffusion/diffusion_benchmark_serving.py \
     ]'
 ```
 
+For a continuous-batching A/B replay, run the same benchmark command twice
+against the two serving configs above and keep traffic plus warmup settings
+identical across both runs. If the measured run uses `--max-concurrency 8`,
+warm with `--warmup-requests 8 --warmup-concurrency 8` so the first measured
+batch does not include compile or CUDA-graph capture overhead.
+
 ---
 
 # 6. Performance Metrics
@@ -163,6 +176,7 @@ To ensure consistent and comparable benchmark results:
 * Record parallel configuration
 * Record benchmark parameters (resolution, concurrency, number of prompts)
 * Ensure no background workload on GPUs during testing
+* When comparing continuous batching, keep warmup settings the same across runs
 
 ---