feat: add dp attention support for Qwen 2/3 MoE models, fixes #6088 (#6121)

Co-authored-by: King.Zevin <zevin@mail.ustc.edu.cn>
Co-authored-by: Yi Zhang <1109276519@qq.com>

python/sglang/srt/models/qwen2_moe.py

@@ -16,6 +16,8 @@
 # https://github.com/vllm-project/vllm/blob/main/vllm/model_executor/models/qwen2_moe.py
 """Inference-only Qwen2MoE model compatible with HuggingFace weights."""
 
+from dataclasses import dataclass
+from enum import Enum, auto
 from typing import Any, Dict, Iterable, Optional, Tuple
 
 import torch
@@ -28,6 +30,15 @@ from sglang.srt.distributed import (
     tensor_model_parallel_all_reduce,
 )
 from sglang.srt.layers.activation import SiluAndMul
+from sglang.srt.layers.dp_attention import (
+    attn_tp_all_gather,
+    attn_tp_reduce_scatter,
+    dp_gather_partial,
+    dp_scatter,
+    get_attention_tp_rank,
+    get_attention_tp_size,
+    get_local_attention_dp_size,
+)
 from sglang.srt.layers.layernorm import RMSNorm
 from sglang.srt.layers.linear import (
     MergedColumnParallelLinear,
@@ -35,7 +46,7 @@ from sglang.srt.layers.linear import (
     ReplicatedLinear,
     RowParallelLinear,
 )
-from sglang.srt.layers.logits_processor import LogitsProcessor
+from sglang.srt.layers.logits_processor import LogitsProcessor, LogitsProcessorOutput
 from sglang.srt.layers.moe.ep_moe.layer import EPMoE
 from sglang.srt.layers.moe.fused_moe_triton import FusedMoE
 from sglang.srt.layers.quantization.base_config import QuantizationConfig
@@ -82,8 +93,7 @@ class Qwen2MoeMLP(nn.Module):
         )
         if hidden_act != "silu":
             raise ValueError(
-                f"Unsupported activation: {hidden_act}. "
-                "Only silu is supported for now."
+                f"Unsupported activation: {hidden_act}. Only silu is supported for now."
             )
         self.act_fn = SiluAndMul()
 
@@ -160,7 +170,6 @@ class Qwen2MoeSparseMoeBlock(nn.Module):
         )
         if shared_output is not None:
             final_hidden_states = final_hidden_states + shared_output
-        if self.tp_size > 1:
             final_hidden_states = tensor_model_parallel_all_reduce(final_hidden_states)
 
         return final_hidden_states.view(num_tokens, hidden_dim)
@@ -182,20 +191,23 @@ class Qwen2MoeAttention(nn.Module):
     ) -> None:
         super().__init__()
         self.hidden_size = hidden_size
-        tp_size = get_tensor_model_parallel_world_size()
+
+        attn_tp_rank = get_attention_tp_rank()
+        attn_tp_size = get_attention_tp_size()
+
         self.total_num_heads = num_heads
-        assert self.total_num_heads % tp_size == 0
-        self.num_heads = self.total_num_heads // tp_size
+        assert self.total_num_heads % attn_tp_size == 0
+        self.num_heads = self.total_num_heads // attn_tp_size
         self.total_num_kv_heads = num_kv_heads
-        if self.total_num_kv_heads >= tp_size:
+        if self.total_num_kv_heads >= attn_tp_size:
             # Number of KV heads is greater than TP size, so we partition
             # the KV heads across multiple tensor parallel GPUs.
-            assert self.total_num_kv_heads % tp_size == 0
+            assert self.total_num_kv_heads % attn_tp_size == 0
         else:
             # Number of KV heads is less than TP size, so we replicate
             # the KV heads across multiple tensor parallel GPUs.
-            assert tp_size % self.total_num_kv_heads == 0
-        self.num_kv_heads = max(1, self.total_num_kv_heads // tp_size)
+            assert attn_tp_size % self.total_num_kv_heads == 0
+        self.num_kv_heads = max(1, self.total_num_kv_heads // attn_tp_size)
         self.head_dim = hidden_size // self.total_num_heads
         self.q_size = self.num_heads * self.head_dim
         self.kv_size = self.num_kv_heads * self.head_dim
@@ -210,6 +222,8 @@ class Qwen2MoeAttention(nn.Module):
             self.total_num_kv_heads,
             bias=qkv_bias,
             quant_config=quant_config,
+            tp_rank=attn_tp_rank,
+            tp_size=attn_tp_size,
             prefix=add_prefix("qkv_proj", prefix),
         )
 
@@ -218,6 +232,9 @@ class Qwen2MoeAttention(nn.Module):
             hidden_size,
             bias=False,
             quant_config=quant_config,
+            tp_rank=attn_tp_rank,
+            tp_size=attn_tp_size,
+            reduce_results=False,
             prefix=add_prefix("o_proj", prefix),
         )
 
@@ -252,6 +269,19 @@ class Qwen2MoeAttention(nn.Module):
         return output
 
 
+class _FFNInputMode(Enum):
+    # The MLP sublayer requires 1/tp_size tokens as input
+    SCATTERED = auto()
+    # The MLP sublayer requires all tokens as input
+    FULL = auto()
+
+
+@dataclass
+class _DecoderLayerInfo:
+    is_sparse: bool
+    ffn_input_mode: _FFNInputMode
+
+
 class Qwen2MoeDecoderLayer(nn.Module):
     def __init__(
         self,
@@ -279,14 +309,21 @@ class Qwen2MoeDecoderLayer(nn.Module):
             prefix=add_prefix("self_attn", prefix),
         )
 
-        # Note: Qwen/Qwen2-57B-A14B-Instruct does not have
-        # `mlp_only_layers` in the config.
-        mlp_only_layers = (
-            [] if not hasattr(config, "mlp_only_layers") else config.mlp_only_layers
+        self.layer_id = layer_id
+
+        self.attn_tp_size = get_attention_tp_size()
+        self.attn_tp_rank = get_attention_tp_rank()
+        self.local_dp_size = get_local_attention_dp_size()
+
+        self.info = self._compute_info(config, layer_id=layer_id)
+        previous_layer_info = self._compute_info(config, layer_id=layer_id - 1)
+        self.input_is_scattered = (
+            layer_id > 0
+            and previous_layer_info.ffn_input_mode == _FFNInputMode.SCATTERED
         )
-        if (layer_id not in mlp_only_layers) and (
-            config.num_experts > 0 and (layer_id + 1) % config.decoder_sparse_step == 0
-        ):
+        self.is_last_layer = self.layer_id == config.num_hidden_layers - 1
+
+        if self.info.is_sparse:
             self.mlp = Qwen2MoeSparseMoeBlock(
                 config=config,
                 quant_config=quant_config,
@@ -305,28 +342,185 @@ class Qwen2MoeDecoderLayer(nn.Module):
             config.hidden_size, eps=config.rms_norm_eps
         )
 
+    @staticmethod
+    def _enable_moe_dense_fully_dp():
+        return global_server_args_dict["moe_dense_tp_size"] == 1
+
+    @staticmethod
+    def _compute_info(config: PretrainedConfig, layer_id: int):
+        # WARN: Qwen2MOE has no dense_layer, it is only for compatibility.
+        mlp_only_layers = (
+            [] if not hasattr(config, "mlp_only_layers") else config.mlp_only_layers
+        )
+        is_sparse = (layer_id not in mlp_only_layers) and (
+            config.num_experts > 0 and (layer_id + 1) % config.decoder_sparse_step == 0
+        )
+        ffn_input_mode = (
+            _FFNInputMode.SCATTERED
+            if (global_server_args_dict["enable_deepep_moe"] and is_sparse)
+            or (Qwen2MoeDecoderLayer._enable_moe_dense_fully_dp() and not is_sparse)
+            else _FFNInputMode.FULL
+        )
+        return _DecoderLayerInfo(is_sparse=is_sparse, ffn_input_mode=ffn_input_mode)
+
     def forward(
         self,
         positions: torch.Tensor,
         hidden_states: torch.Tensor,
         forward_batch: ForwardBatch,
         residual: Optional[torch.Tensor],
-    ) -> torch.Tensor:
-        # Self Attention
-        if residual is None:
-            residual = hidden_states
-            hidden_states = self.input_layernorm(hidden_states)
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        if self.info.ffn_input_mode == _FFNInputMode.SCATTERED:
+            return self.forward_ffn_with_scattered_input(
+                positions, hidden_states, forward_batch, residual
+            )
+        elif self.info.ffn_input_mode == _FFNInputMode.FULL:
+            return self.forward_ffn_with_full_input(
+                positions, hidden_states, forward_batch, residual
+            )
         else:
-            hidden_states, residual = self.input_layernorm(hidden_states, residual)
-        hidden_states = self.self_attn(
-            positions=positions,
-            hidden_states=hidden_states,
-            forward_batch=forward_batch,
-        )
+            raise NotImplementedError
+
+    def forward_ffn_with_full_input(
+        self,
+        positions: torch.Tensor,
+        hidden_states: torch.Tensor,
+        forward_batch: ForwardBatch,
+        residual: Optional[torch.Tensor],
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        if hidden_states.shape[0] == 0:
+            residual = hidden_states
+        else:
+            if residual is None:
+                residual = hidden_states
+                hidden_states = self.input_layernorm(hidden_states)
+            else:
+                hidden_states, residual = self.input_layernorm(hidden_states, residual)
+
+            # Self Attention
+            hidden_states = self.self_attn(
+                positions=positions,
+                hidden_states=hidden_states,
+                forward_batch=forward_batch,
+            )
+        # Gather
+        if get_tensor_model_parallel_world_size() > 1:
+            # all gather and all reduce
+            if self.local_dp_size != 1:
+                if self.attn_tp_rank == 0:
+                    hidden_states += residual
+                hidden_states, local_hidden_states = (
+                    forward_batch.gathered_buffer,
+                    hidden_states,
+                )
+                dp_gather_partial(hidden_states, local_hidden_states, forward_batch)
+                dp_scatter(residual, hidden_states, forward_batch)
+                # TODO extract this bugfix
+                if hidden_states.shape[0] != 0:
+                    hidden_states = self.post_attention_layernorm(hidden_states)
+            else:
+                hidden_states = tensor_model_parallel_all_reduce(hidden_states)
+                # TODO extract this bugfix
+                if hidden_states.shape[0] != 0:
+                    hidden_states, residual = self.post_attention_layernorm(
+                        hidden_states, residual
+                    )
+        elif hidden_states.shape[0] != 0:
+            hidden_states, residual = self.post_attention_layernorm(
+                hidden_states, residual
+            )
 
         # Fully Connected
-        hidden_states, residual = self.post_attention_layernorm(hidden_states, residual)
         hidden_states = self.mlp(hidden_states)
+
+        # TODO: use reduce-scatter in MLP to avoid this scatter
+        # Scatter
+        if self.local_dp_size != 1:
+            # important: forward batch.gathered_buffer is used both after scatter and after gather.
+            # be careful about this!
+            hidden_states, global_hidden_states = (
+                forward_batch.gathered_buffer[: forward_batch.input_ids.shape[0]],
+                hidden_states,
+            )
+            dp_scatter(hidden_states, global_hidden_states, forward_batch)
+
+        return hidden_states, residual
+
+    def forward_ffn_with_scattered_input(
+        self,
+        positions: torch.Tensor,
+        hidden_states: torch.Tensor,
+        forward_batch: ForwardBatch,
+        residual: Optional[torch.Tensor],
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        if hidden_states.shape[0] == 0:
+            residual = hidden_states
+        else:
+            if residual is None:
+                residual = hidden_states
+                hidden_states = self.input_layernorm(hidden_states)
+            else:
+                hidden_states, residual = self.input_layernorm(hidden_states, residual)
+
+        if self.attn_tp_size != 1 and self.input_is_scattered:
+            hidden_states, local_hidden_states = (
+                forward_batch.gathered_buffer[: forward_batch.input_ids.shape[0]],
+                hidden_states,
+            )
+            attn_tp_all_gather(
+                list(hidden_states.tensor_split(self.attn_tp_size)), local_hidden_states
+            )
+
+        # Self Attention
+        if hidden_states.shape[0] != 0:
+            hidden_states = self.self_attn(
+                positions=positions,
+                hidden_states=hidden_states,
+                forward_batch=forward_batch,
+            )
+
+        if self.attn_tp_size != 1:
+            if self.input_is_scattered:
+                tensor_list = list(hidden_states.tensor_split(self.attn_tp_size))
+                hidden_states = tensor_list[self.attn_tp_rank]
+                attn_tp_reduce_scatter(hidden_states, tensor_list)
+                if hidden_states.shape[0] != 0:
+                    hidden_states, residual = self.post_attention_layernorm(
+                        hidden_states, residual
+                    )
+            else:
+                if self.attn_tp_rank == 0:
+                    hidden_states += residual
+                tensor_list = list(hidden_states.tensor_split(self.attn_tp_size))
+                hidden_states = tensor_list[self.attn_tp_rank]
+                attn_tp_reduce_scatter(hidden_states, tensor_list)
+                residual = hidden_states
+                if hidden_states.shape[0] != 0:
+                    hidden_states = self.post_attention_layernorm(hidden_states)
+        else:
+            if hidden_states.shape[0] != 0:
+                hidden_states, residual = self.post_attention_layernorm(
+                    hidden_states, residual
+                )
+
+        if not (
+            self._enable_moe_dense_fully_dp()
+            and (not self.info.is_sparse)
+            and hidden_states.shape[0] == 0
+        ):
+            hidden_states = self.mlp(hidden_states, forward_batch.forward_mode)
+
+        if self.is_last_layer and self.attn_tp_size != 1:
+            hidden_states += residual
+            residual = None
+            hidden_states, local_hidden_states = (
+                forward_batch.gathered_buffer[: forward_batch.input_ids.shape[0]],
+                hidden_states,
+            )
+            attn_tp_all_gather(
+                list(hidden_states.tensor_split(self.attn_tp_size)), local_hidden_states
+            )
+
         return hidden_states, residual
 
 
@@ -345,6 +539,7 @@ class Qwen2MoeModel(nn.Module):
         self.embed_tokens = VocabParallelEmbedding(
             config.vocab_size,
             config.hidden_size,
+            enable_tp=not global_server_args_dict["enable_dp_attention"],
             prefix=add_prefix("embed_tokens", prefix),
         )
         # Use the provided decoder layer type or default to Qwen2MoeDecoderLayer
@@ -379,12 +574,12 @@ class Qwen2MoeModel(nn.Module):
             hidden_states, residual = layer(
                 positions, hidden_states, forward_batch, residual
             )
-        hidden_states, _ = self.norm(hidden_states, residual)
+        if hidden_states.shape[0] != 0:
+            hidden_states, _ = self.norm(hidden_states, residual)
         return hidden_states
 
 
 class Qwen2MoeForCausalLM(nn.Module):
-
     fall_back_to_pt_during_load = False
 
     def __init__(
@@ -414,7 +609,7 @@ class Qwen2MoeForCausalLM(nn.Module):
         positions: torch.Tensor,
         forward_batch: ForwardBatch,
         input_embeds: torch.Tensor = None,
-    ) -> torch.Tensor:
+    ) -> LogitsProcessorOutput:
         hidden_states = self.model(input_ids, positions, forward_batch, input_embeds)
         return self.logits_processor(
             input_ids, hidden_states, self.lm_head, forward_batch