[Feature][Diffusion] Allow online INT8 quantization with DLO AllGather (#6573)

Signed-off-by: brandneway <gyuan4892@gmail.com>

tests/diffusion/model_loader/test_diffusers_loader.py

@@ -273,12 +273,15 @@ def test_required_hwr_miss_fails_before_ordinary_loading_or_publication(
     assert loader.take_host_weight_plan() is None
 
 
-def _make_dlo_online_quant_config() -> OmniDiffusionConfig:
+def _make_dlo_online_quant_config(dp_size: int = 2) -> OmniDiffusionConfig:
     return OmniDiffusionConfig(
         model="",
         dtype=torch.float32,
         quantization_config="fp8",
-        parallel_config=DiffusionParallelConfig(data_parallel_size=2),
+        parallel_config=DiffusionParallelConfig(
+            data_parallel_size=dp_size,
+            sequence_parallel_size=1,
+        ),
         enable_distributed_layerwise_offload=True,
         dlo_use_allgather=True,
     )
@@ -824,6 +827,93 @@ def test_dlo_allgather_online_fp8_uses_ordinary_loader(monkeypatch):
     assert loader.take_host_weight_plan() is None
 
 
+def test_dlo_allgather_online_int8_uses_ordinary_loader(monkeypatch):
+    import vllm_omni.diffusion.model_loader.diffusers_loader as loader_mod
+    from vllm_omni.quantization.int8_config import NPUInt8OnlineLinearMethod
+
+    od_config = _make_dlo_online_quant_config()
+    loader = DiffusersPipelineLoader(LoadConfig(), od_config)
+    model = nn.Module()
+    model.transformer = nn.Linear(2, 2, bias=False)
+    model.transformer.quant_method = object.__new__(NPUInt8OnlineLinearMethod)
+    model.transformer.quant_method.uses_meta_device = True
+    calls: list[object] = []
+    allowlist_models: list[nn.Module] = []
+
+    original_allowlist_check = loader._unsupported_dlo_allgather_online_quant_methods
+
+    def check_allowlist(candidate: nn.Module) -> tuple[str, ...]:
+        allowlist_models.append(candidate)
+        return original_allowlist_check(candidate)
+
+    loader._init_from_load_format = lambda *_args, **_kwargs: model  # type: ignore[method-assign]
+    monkeypatch.setattr(loader, "_unsupported_dlo_allgather_online_quant_methods", check_allowlist)
+    loader._request_offload_after_quant = lambda _model: 1  # type: ignore[method-assign]
+    loader.load_weights = (  # type: ignore[method-assign]
+        lambda _model, *, stream_online_quant_to_cpu=False: calls.append(("load", stream_online_quant_to_cpu))
+    )
+    loader._process_weights_after_loading = lambda *_args: calls.append("process")  # type: ignore[method-assign]
+    loader._apply_skip_softmax_calibration = lambda _model: None  # type: ignore[method-assign]
+    monkeypatch.setattr(
+        loader_mod,
+        "build_checkpoint_mmap_plan",
+        lambda *_args, **_kwargs: HostWeightPlanResult(
+            None,
+            "online quantization requires the ordinary loader",
+        ),
+    )
+
+    assert loader.load_model(load_device="cpu", device=torch.device("cpu")) is model
+    assert allowlist_models == [model]
+    assert calls == [("load", True), "process"]
+    assert loader.take_host_weight_plan() is None
+
+
+def test_dlo_online_quant_group_size_one_skips_allgather_gate(monkeypatch):
+    """A DLO group of one runs no weight collective, so an otherwise
+    unvalidated online method must not be rejected by the AllGather gate."""
+
+    class UnsupportedOnlineMethod:
+        uses_meta_device = True
+
+    import vllm_omni.diffusion.model_loader.diffusers_loader as loader_mod
+
+    od_config = _make_dlo_online_quant_config(dp_size=1)
+    loader = DiffusersPipelineLoader(LoadConfig(), od_config)
+    model = nn.Module()
+    model.transformer = nn.Linear(2, 2, bias=False)
+    model.transformer.quant_method = UnsupportedOnlineMethod()
+    calls: list[object] = []
+    allowlist_models: list[nn.Module] = []
+
+    original_allowlist_check = loader._unsupported_dlo_allgather_online_quant_methods
+
+    def check_allowlist(candidate: nn.Module) -> tuple[str, ...]:
+        allowlist_models.append(candidate)
+        return original_allowlist_check(candidate)
+
+    loader._init_from_load_format = lambda *_args, **_kwargs: model  # type: ignore[method-assign]
+    monkeypatch.setattr(loader, "_unsupported_dlo_allgather_online_quant_methods", check_allowlist)
+    loader._request_offload_after_quant = lambda _model: 1  # type: ignore[method-assign]
+    loader.load_weights = (  # type: ignore[method-assign]
+        lambda _model, *, stream_online_quant_to_cpu=False: calls.append(("load", stream_online_quant_to_cpu))
+    )
+    loader._process_weights_after_loading = lambda *_args: calls.append("process")  # type: ignore[method-assign]
+    loader._apply_skip_softmax_calibration = lambda _model: None  # type: ignore[method-assign]
+    monkeypatch.setattr(
+        loader_mod,
+        "build_checkpoint_mmap_plan",
+        lambda *_args, **_kwargs: HostWeightPlanResult(
+            None,
+            "online quantization requires the ordinary loader",
+        ),
+    )
+
+    assert loader.load_model(load_device="cpu", device=torch.device("cpu")) is model
+    assert allowlist_models == []
+    assert calls == [("load", True), "process"]
+
+
 def test_dlo_allgather_rejects_unvalidated_online_quant_method(monkeypatch):
     import vllm_omni.diffusion.model_loader.diffusers_loader as loader_mod
 
@@ -847,10 +937,54 @@ def test_dlo_allgather_rejects_unvalidated_online_quant_method(monkeypatch):
         ),
     )
 
-    with pytest.raises(ValueError, match="per-tensor FP8 linears"):
+    with pytest.raises(ValueError, match="per-tensor FP8, INT8, and MXFP8 linears"):
         loader.load_model(load_device="cpu")
 
 
+def test_dlo_allgather_online_mxfp8_uses_ordinary_loader(monkeypatch):
+    mxfp8_config = pytest.importorskip("vllm_omni.quantization.mxfp8_config")
+    NPUMxfp8OnlineLinearMethod = mxfp8_config.NPUMxfp8OnlineLinearMethod
+
+    import vllm_omni.diffusion.model_loader.diffusers_loader as loader_mod
+
+    od_config = _make_dlo_online_quant_config()
+    loader = DiffusersPipelineLoader(LoadConfig(), od_config)
+    model = nn.Module()
+    model.transformer = nn.Linear(2, 2, bias=False)
+    model.transformer.quant_method = object.__new__(NPUMxfp8OnlineLinearMethod)
+    model.transformer.quant_method.uses_meta_device = True
+    calls: list[object] = []
+    allowlist_models: list[nn.Module] = []
+
+    original_allowlist_check = loader._unsupported_dlo_allgather_online_quant_methods
+
+    def check_allowlist(candidate: nn.Module) -> tuple[str, ...]:
+        allowlist_models.append(candidate)
+        return original_allowlist_check(candidate)
+
+    loader._init_from_load_format = lambda *_args, **_kwargs: model  # type: ignore[method-assign]
+    monkeypatch.setattr(loader, "_unsupported_dlo_allgather_online_quant_methods", check_allowlist)
+    loader._request_offload_after_quant = lambda _model: 1  # type: ignore[method-assign]
+    loader.load_weights = (  # type: ignore[method-assign]
+        lambda _model, *, stream_online_quant_to_cpu=False: calls.append(("load", stream_online_quant_to_cpu))
+    )
+    loader._process_weights_after_loading = lambda *_args: calls.append("process")  # type: ignore[method-assign]
+    loader._apply_skip_softmax_calibration = lambda _model: None  # type: ignore[method-assign]
+    monkeypatch.setattr(
+        loader_mod,
+        "build_checkpoint_mmap_plan",
+        lambda *_args, **_kwargs: HostWeightPlanResult(
+            None,
+            "online quantization requires the ordinary loader",
+        ),
+    )
+
+    assert loader.load_model(load_device="cpu", device=torch.device("cpu")) is model
+    assert allowlist_models == [model]
+    assert calls == [("load", True), "process"]
+    assert loader.take_host_weight_plan() is None
+
+
 def test_hsdp_processes_quantized_weights_before_sharding(mocker):
     import vllm_omni.diffusion.model_loader.diffusers_loader as loader_mod
     from vllm_omni.diffusion.offloader.module_collector import PipelineModules