[main] mlp weight prefetch in Qwen Dense Models (#2816)

### What this PR does / why we need it?
This PR prefetchs the weight of mlp layers in Qwen Dense Models to
optimize the performance in Decode phase mainly.

### Does this PR introduce _any_ user-facing change?
 No.

### How was this patch tested?
CI passed with new added/existing test.

- vLLM version: main
- vLLM main:
vllm-project/vllm@a1213fa

Signed-off-by: rjg-lyh <[email protected]>
Co-authored-by: Shuming19 <[email protected]>

Author: rjg-lyh

.github/workflows/vllm_ascend_test.yaml

@@ -258,4 +258,4 @@ jobs:
           VLLM_WORKER_MULTIPROC_METHOD: spawn
           VLLM_USE_MODELSCOPE: True
         run: |
-          pytest -sv tests/e2e/multicard/test_qwen3_moe.py::test_models_distributed_Qwen3_MOE_TP2_WITH_EP
+          pytest -sv tests/e2e/multicard/test_qwen3_moe.py::test_models_distributed_Qwen3_MOE_TP2_WITH_EP

.github/workflows/vllm_ascend_test_full.yaml

@@ -226,6 +226,8 @@ jobs:
           pytest -sv tests/e2e/multicard/test_offline_inference_distributed.py::test_models_distributed_Qwen3_W4A8DYNAMIC
           pytest -sv tests/e2e/multicard/test_offline_inference_distributed.py::test_models_distributed_DeepSeek_W4A8DYNAMIC
           pytest -sv tests/e2e/multicard/test_offline_inference_distributed.py::test_sp_for_qwen3_moe
+          pytest -sv tests/e2e/multicard/test_offline_inference_distributed.py::test_models_distributed_Qwen_Dense_with_flashcomm_v1
+          pytest -sv tests/e2e/multicard/test_offline_inference_distributed.py::test_models_distributed_Qwen_Dense_with_prefetch_mlp_weight
 
           #pytest -sv tests/e2e/multicard/test_pipeline_parallel.py
           pytest -sv tests/e2e/multicard/test_prefix_caching.py

tests/e2e/multicard/test_offline_inference_distributed.py

@@ -31,7 +31,9 @@
 
 os.environ["PYTORCH_NPU_ALLOC_CONF"] = "max_split_size_mb:256"
 
-QWEN_DENSE_MODELS = ["Qwen/QwQ-32B", "Qwen/Qwen-32B"]
+QWEN_DENSE_MODELS = [
+    "vllm-ascend/Qwen3-8B-W8A8", "vllm-ascend/Qwen2.5-0.5B-Instruct-W8A8"
+]
 
 
 def test_models_distributed_QwQ():
@@ -170,6 +172,29 @@ def test_models_distributed_Qwen_Dense_with_flashcomm_v1(model, enforce_eager):
             max_model_len=8192,
             enforce_eager=enforce_eager,
             dtype="auto",
-            tensor_parallel_size=4,
+            tensor_parallel_size=2,
+            quantization="ascend",
+    ) as vllm_model:
+        vllm_model.generate_greedy(example_prompts, max_tokens)
+
+
+@pytest.mark.parametrize("enforce_eager", [True, False])
+@pytest.mark.parametrize("model", QWEN_DENSE_MODELS)
+@patch.dict(os.environ, {"VLLM_ASCEND_ENABLE_DENSE_OPTIMIZE": "1"})
+@patch.dict(os.environ, {"VLLM_ASCEND_ENABLE_PREFETCH_MLP": "1"})
+def test_models_distributed_Qwen_Dense_with_prefetch_mlp_weight(
+        model, enforce_eager):
+    example_prompts = [
+        "Hello, my name is",
+    ]
+    max_tokens = 5
+
+    with VllmRunner(
+            snapshot_download(model),
+            max_model_len=8192,
+            enforce_eager=enforce_eager,
+            dtype="auto",
+            tensor_parallel_size=2,
+            quantization="ascend",
     ) as vllm_model:
         vllm_model.generate_greedy(example_prompts, max_tokens)

tests/ut/ops/test_activation.py

@@ -38,7 +38,12 @@ def test_QuickGELU_forward(mock_gelu, dummy_tensor):
 
 @pytest.mark.parametrize("is_310p_return", [True, False])
 @patch("torch_npu.npu_swiglu", side_effect=lambda x: x + 1)
-def test_SiluAndMul_forward(mock_swiglu, is_310p_return, dummy_tensor):
+@patch("torch.ops.vllm.maybe_wait_prefetch_done", side_effect=lambda x: None)
+@patch("torch.ops.vllm.maybe_prefetch_mlp_down_proj",
+       side_effect=lambda x: None)
+def test_SiluAndMul_forward(mock_maybe_prefetch_mlp_down_proj,
+                            mock_maybe_wait_prefetch_done, mock_swiglu,
+                            is_310p_return, dummy_tensor):
 
     with patch("vllm_ascend.utils.is_310p", return_value=is_310p_return):
         layer = SiluAndMul()
@@ -49,9 +54,15 @@ def test_SiluAndMul_forward(mock_swiglu, is_310p_return, dummy_tensor):
         else:
             expected_arg = dummy_tensor
 
+        # assert mock_maybe_prefetch_mlp_down_proj.call_count == 1
+        mock_maybe_prefetch_mlp_down_proj.assert_called_once()
+
         # assert mock_swiglu.call_count == 1
         mock_swiglu.assert_called_once()
 
+        # assert mock_maybe_wait_prefetch_done.call_count == 1
+        mock_maybe_wait_prefetch_done.assert_called_once()
+
         actual_arg = mock_swiglu.call_args[0][0]
         assert torch.allclose(
             actual_arg,

tests/ut/ops/test_layernorm.py

@@ -30,9 +30,11 @@ def mock_add_rms_norm(x, residual, weight, eps):
                          [None, torch.randn(4, 8, dtype=torch.float32)])
 @patch("torch_npu.npu_rms_norm", side_effect=mock_rms_norm)
 @patch("torch_npu.npu_add_rms_norm", side_effect=mock_add_rms_norm)
+@patch("torch.ops.vllm.maybe_wait_prefetch_done", side_effect=lambda x: None)
 @patch("torch.ops.vllm.maybe_chunk_residual",
        side_effect=mock_maybe_chunk_residual)
-def test_RMSNorm_forward(mock_maybe_chunk_residual, mock_add_rmsnorm,
+def test_RMSNorm_forward(mock_maybe_chunk_residual,
+                         mock_maybe_wait_prefetch_done, mock_add_rmsnorm,
                          mock_rmsnorm, is_310p_return, residual, dummy_tensor):
 
     with patch("vllm_ascend.utils.is_310p", return_value=is_310p_return):
@@ -45,13 +47,17 @@ def test_RMSNorm_forward(mock_maybe_chunk_residual, mock_add_rmsnorm,
                 expected_out_x = expected_arg_x + 1
                 expected_out_residual = expected_arg_x.to(residual.dtype)
 
+                mock_maybe_chunk_residual.assert_called_once()
                 mock_rmsnorm.assert_called_once()
+                mock_maybe_wait_prefetch_done.assert_called_once()
                 assert torch.allclose(out_x, expected_out_x)
                 assert torch.allclose(out_residual, expected_out_residual)
             else:
                 expected_out_x = 2 * dummy_tensor
                 expected_out_residual = 2 * residual
+                mock_maybe_chunk_residual.assert_called_once()
                 mock_add_rmsnorm.assert_called_once()
+                mock_maybe_wait_prefetch_done.assert_called_once()
                 assert torch.allclose(out_x, expected_out_x)
                 assert torch.allclose(out_residual, expected_out_residual)
         else:
@@ -64,9 +70,11 @@ def test_RMSNorm_forward(mock_maybe_chunk_residual, mock_add_rmsnorm,
 
 @patch("vllm_ascend.utils.is_310p", return_value=False)
 @patch("torch_npu.npu_add_rms_norm", side_effect=mock_add_rms_norm)
+@patch("torch.ops.vllm.maybe_wait_prefetch_done", side_effect=lambda x: None)
 @patch("torch.ops.vllm.maybe_chunk_residual",
        side_effect=mock_maybe_chunk_residual)
 def test_RMSNorm_forward_with_flashcomm_v1(mock_maybe_chunk_residual,
+                                           mock_maybe_wait_prefetch_done,
                                            mock_add_rms_norm, mock_is310p):
     x = torch.randn(4, 512, dtype=torch.bfloat16)
     residual = torch.randn(16, 512, dtype=torch.bfloat16)
@@ -79,6 +87,7 @@ def test_RMSNorm_forward_with_flashcomm_v1(mock_maybe_chunk_residual,
 
     mock_maybe_chunk_residual.assert_called_once()
     mock_add_rms_norm.assert_called_once()
+    mock_maybe_wait_prefetch_done.assert_called_once()
     assert out_residual.size(0) == 4
     assert torch.allclose(out_x, expected_out_x)
     assert torch.allclose(out_residual, expected_out_residual)

tests/ut/torchair/models/test_torchair_deepseek_v2.py

@@ -275,7 +275,12 @@ def test_torchair_deepseek_v2_mla_attention(mock_rms_norm, mock_distributed,
 
 @patch("torch_npu.npu_add_rms_norm")
 @patch("torch_npu.npu_rms_norm")
-def test_torchair_deepseek_v2_decoder_layer(mock_rms_norm, mock_add_norm,
+@patch("torch.ops.vllm.maybe_wait_prefetch_done", side_effect=lambda x: None)
+@patch("torch.ops.vllm.maybe_chunk_residual",
+       side_effect=lambda x, residual: residual)
+def test_torchair_deepseek_v2_decoder_layer(mock_maybe_chunk_residual,
+                                            mock_maybe_wait_prefetch_done,
+                                            mock_rms_norm, mock_add_norm,
                                             mock_distributed, base_config,
                                             vllm_config):
     mock_rms_norm.return_value = (torch.randn(2, 128), torch.randn(2, 128))

vllm_ascend/ascend_forward_context.py

@@ -66,7 +66,9 @@ def set_ascend_forward_context(
         moe_comm_method: str = "",
         num_actual_tokens: Optional[int] = None,
         aclgraph_runtime_mode: CUDAGraphMode = CUDAGraphMode.NONE,
-        batch_descriptor: Optional[BatchDescriptor] = None):
+        batch_descriptor: Optional[BatchDescriptor] = None,
+        prefetch_stream: torch.npu.Stream = None,
+        model_instance: torch.nn.Module = None):
     """A context manager that stores the current forward context,
     can be attention metadata, etc.
     We add some additional param into forward_context.
@@ -108,7 +110,8 @@ def set_ascend_forward_context(
         # Currently, it is an empirical value. In normal scenarios, if the concurrency exceeds this threshold,
         # the performance benefits can be maximized. Conversely, if the concurrency is below the threshold,
         # the performance may degrade due to the switching of communication methods.
-        flashcomm_v1_enabled = envs_ascend.VLLM_ASCEND_ENABLE_FLASHCOMM and \
+        flashcomm_v1_enabled = envs_ascend.VLLM_ASCEND_ENABLE_DENSE_OPTIMIZE and \
+            envs_ascend.VLLM_ASCEND_ENABLE_FLASHCOMM and \
             tp_world_size > 1 and \
             num_tokens is not None and num_tokens > 1000
 
@@ -122,6 +125,26 @@ def set_ascend_forward_context(
         # set this for rope forward_oot using
         forward_context.is_first_layer = True
 
+        # set layer_idx to enable optimization features that depend on this information.
+        # This is only applicable to models that contain these necessary attributes.
+        forward_context.layer_idx = None
+        if model_instance is not None and \
+            hasattr(model_instance, "model") and \
+            hasattr(model_instance.model, "start_layer"):
+            forward_context.layer_idx = model_instance.model.start_layer
+
+        # set for mlp weight prefetch
+        prefetch_mlp_enabled = envs_ascend.VLLM_ASCEND_ENABLE_DENSE_OPTIMIZE and \
+            envs_ascend.VLLM_ASCEND_ENABLE_PREFETCH_MLP and \
+            forward_context.layer_idx is not None and \
+            num_tokens is not None and num_tokens < 500
+        if prefetch_mlp_enabled:
+            forward_context.prefetch_stream = prefetch_stream
+            forward_context.model_instance = model_instance
+            forward_context.prefetch_mlp_gate_up_proj = False
+            forward_context.prefetch_mlp_down_proj = False
+        forward_context.prefetch_mlp_enabled = prefetch_mlp_enabled
+
         if num_tokens is None and attn_metadata is not None:
             num_tokens = attn_metadata.num_actual_tokens
 

vllm_ascend/envs.py

@@ -135,6 +135,15 @@
     # This feature will get better performance when concurrency is large.
     "VLLM_ASCEND_ENABLE_FLASHCOMM":
     lambda: bool(int(os.getenv("VLLM_ASCEND_ENABLE_FLASHCOMM", '0'))),
+    # Whether to enable MLP weight prefetch, only used in small concurrency.
+    "VLLM_ASCEND_ENABLE_PREFETCH_MLP":
+    lambda: bool(int(os.getenv("VLLM_ASCEND_ENABLE_PREFETCH_MLP", '0'))),
+    # buffer size for gate up prefetch
+    "MLP_GATE_UP_PREFETCH_SIZE":
+    lambda: int(os.getenv("MLP_GATE_UP_PREFETCH_SIZE", 18 * 1024 * 1024)),
+    # buffer size for down proj prefetch
+    "MLP_DOWN_PREFETCH_SIZE":
+    lambda: int(os.getenv("MLP_DOWN_PREFETCH_SIZE", 18 * 1024 * 1024)),
     # Whether to enable dense model and general optimizations for better performance.
     # Since we modified the base parent class `linear`, this optimization is also applicable to other model types.
     # However, there might be hidden issues, and it is currently recommended to prioritize its use with dense models.

vllm_ascend/ops/activation.py

@@ -35,8 +35,10 @@ def forward_oot(self, x: torch.Tensor) -> torch.Tensor:
 
         from vllm_ascend.utils import is_310p
 
+        torch.ops.vllm.maybe_prefetch_mlp_down_proj(x)
         if is_310p():
             out = torch_npu.npu_swiglu(x.to(torch.float32)).to(torch.float16)
         else:
             out = torch_npu.npu_swiglu(x)
+        torch.ops.vllm.maybe_wait_prefetch_done(out)
         return out

vllm_ascend/ops/layernorm.py

@@ -44,12 +44,7 @@ def forward(
         import torch_npu
 
         if residual is not None:
-            # FIXME(rjg-lyh): This is a hacky way to chunk residuals when the flashcomm_v1 feature
-            # is enabled, without interfering with the normal operation of components like torchair.
-            # The final solution should be to move this check into the operator and support
-            # integration with torchair.
-            if x.size(0) != residual.size(0):
-                residual = torch.ops.vllm.maybe_chunk_residual(x, residual)
+            residual = torch.ops.vllm.maybe_chunk_residual(x, residual)
             assert x.size(0) == residual.size(0)
             x, _, residual = torch_npu.npu_add_rms_norm_quant(
                 x,
@@ -58,6 +53,7 @@ def forward(
                 self.layer.aclnn_input_scale,
                 self.layer.aclnn_input_offset,
                 epsilon=self.variance_epsilon)
+            torch.ops.vllm.maybe_wait_prefetch_done(x)
             return x, residual
 
         x, residual = torch_npu.npu_rms_norm(x, self.weight,
@@ -76,12 +72,7 @@ def forward_oot(
 
         from vllm_ascend.utils import is_310p
         if residual is not None:
-            # FIXME(rjg-lyh): This is a hacky way to chunk residuals when the flashcomm_v1 feature
-            # is enabled, without interfering with the normal operation of components like torchair.
-            # The final solution should be to move this check into the operator and support
-            # integration with torchair.
-            if x.size(0) != residual.size(0):
-                residual = torch.ops.vllm.maybe_chunk_residual(x, residual)
+            residual = torch.ops.vllm.maybe_chunk_residual(x, residual)
             assert x.size(0) == residual.size(0)
             if is_310p():
                 orig_dtype = residual.dtype
@@ -92,6 +83,7 @@ def forward_oot(
             else:
                 x, _, residual = torch_npu.npu_add_rms_norm(
                     x, residual, self.weight, self.variance_epsilon)
+            torch.ops.vllm.maybe_wait_prefetch_done(x)
             return x, residual
 
         x, residual = torch_npu.npu_rms_norm(x, self.weight,