fix: Phase B 实测回归(flex+dense慢5-6x)，默认回退 sdpa+loop；bench 加 --profile

实测 A800：sdpa+loop=15.15s，flex+dense=98s，+compile=82s。模型是开销瓶颈
非算力瓶颈(30TFLOP应0.15s却跑15s)，FlexAttention解决的算力问题非此处瓶颈、
反增开销。默认改回已验证最快的 sdpa+loop。新增 bench --profile 用 torch.profiler
定位真正的开销来源(算子级)。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

代码/code/bench.py

@@ -160,6 +160,47 @@ def run_diag(rebuild=False):
           f"超界sign占比={over}/{tot}={(over / max(tot, 1)):.2%}")
 
 
+def run_profile(config_override=None, n=20, batch_size=50, rebuild=False):
+    """用 torch.profiler 剖析前 n 个 batch，打印按 CUDA 耗时排序的算子表，定位真正瓶颈。"""
+    if config_override is None:
+        config_override = {}
+    infer.CONFIG.update(config_override)
+    cur = Path(__file__).parent
+    ref = cur / "dataset"
+    item_dict, user_seq = _get_data(cur, ref, rebuild=rebuild)
+    test_logids = infer.load_logids_from_file(ref / "test.csv")
+    ds = infer.CTRTestSeqDataset(
+        test_logids_ordered=list(test_logids), item_dict=item_dict,
+        user_seq=user_seq, max_feasign_per_slot={1: 2}, max_ctx_len=None)
+    loader = DataLoader(ds, batch_size=batch_size, shuffle=False, num_workers=0,
+                        collate_fn=infer.make_collate_fn(ds.max_slot_id))
+    batches = []
+    for b in loader:
+        batches.append(infer.move_batch_to_device(b, torch.device("cpu")))
+        if len(batches) >= n:
+            break
+    del item_dict, user_seq, ds, loader
+    import gc
+    gc.collect()
+    model, dev = infer.load_model(ckpt_path=None)
+    cuda = (dev.type == "cuda")
+    from torch.profiler import profile, ProfilerActivity
+    acts = [ProfilerActivity.CPU] + ([ProfilerActivity.CUDA] if cuda else [])
+    with torch.inference_mode():
+        warm = infer.move_batch_to_device(batches[0], dev)  # 预热（触发任何首次编译）
+        model(warm)
+        if cuda:
+            torch.cuda.synchronize()
+        with profile(activities=acts) as prof:
+            for b in batches:
+                b = infer.move_batch_to_device(b, dev)
+                model(b)
+                if cuda:
+                    torch.cuda.synchronize()
+    sort_key = "cuda_time_total" if cuda else "cpu_time_total"
+    print(prof.key_averages().table(sort_by=sort_key, row_limit=25))
+
+
 def run_once(config_override=None, batch_size=50, max_batches=None,
              max_feasign_per_slot=None, rebuild=False):
     """跑一次本地推理并打分。返回 infer._cal_score 的结果 dict。"""
@@ -255,6 +296,8 @@ def _parse_args():
     ap.add_argument("--moe", choices=["dense", "loop"], default=None,
                     help="MoE实现：dense=向量化(新), loop=逐expert循环(原)")
     ap.add_argument("--compile", action="store_true", help="开启 torch.compile")
+    ap.add_argument("--profile", type=int, default=None, metavar="N",
+                    help="剖析前 N 个 batch，打印按 CUDA 耗时排序的算子表（定位瓶颈）")
     ap.add_argument("--rebuild", action="store_true", help="强制重建过滤缓存")
     return ap.parse_args()
 
@@ -284,5 +327,8 @@ if __name__ == "__main__":
         cfg["vectorize_moe"] = (a.moe == "dense")
     if a.compile:
         cfg["compile"] = True
+    if a.profile is not None:
+        run_profile(cfg, n=a.profile, batch_size=a.bs, rebuild=a.rebuild)
+        sys.exit(0)
     mf = None if a.feasign_none else {1: 2}
     run_once(cfg, batch_size=a.bs, max_batches=a.smoke, max_feasign_per_slot=mf, rebuild=a.rebuild)

代码/code/infer.py

@@ -40,9 +40,11 @@ CONFIG = {
     "signid_mode": "clamp",   # "clamp" 或 "modulo"：处理超界 sign id 的方式
     "sync_timing": False,     # bench 里设 True，做 torch.cuda.synchronize 真实计时
     "filter_test_users": True,  # 只处理含测试样本的用户（跳过会被丢弃的用户，省算力）
-    "use_flex_attn": "auto",  # "auto"(SM80+用flex,否则SDPA) / True / False
-    "vectorize_moe": True,    # True=稠密向量化MoE（无Python循环/同步）；False=原逐expert循环
-    "compile": False,         # 是否 torch.compile（图理干净后再开）
+    # 实测：FlexAttention + 稠密MoE 在本模型上反而慢 5-6 倍（模型是开销瓶颈非算力瓶颈），
+    # 故默认回到已验证最快的 sdpa + loop；flex/dense 仅作 bench 对照选项。
+    "use_flex_attn": False,   # "auto"(SM80+用flex,否则SDPA) / True / False
+    "vectorize_moe": False,   # True=稠密向量化MoE；False=原逐expert循环（默认，已验证更快）
+    "compile": False,         # 是否 torch.compile
 }