Support (1 <= dp < tp) in the dp attention in DeepEP (#4770)

Co-authored-by: Cheng Wan <cwan39@gatech.edu>

docs/backend/server_arguments.md

@@ -90,7 +90,7 @@ Please consult the documentation below to learn more about the parameters you ma
 ### Expert parallelism
 * `enable_ep_moe`: Enables expert parallelism that distributes the experts onto multiple GPUs for MoE models.
 * `ep_size`: The size of EP. Please shard the model weights with `tp_size=ep_size`, for detailed benchmarking refer to [this PR](https://github.com/sgl-project/sglang/pull/2203). If not set, `ep_size` will be automatically set to `tp_size`.
-* `enable_deepep_moe`: Enables expert parallelism that distributes the experts onto multiple GPUs for DeepSeek-V3 model based on deepseek-ai/DeepEP. Currently DeepEP is bind to DP Attention. Please set `--enable-dp-attention --enable-deepep-moe`, perfer `tp_size=dp_size=ep_size`.
+* `enable_deepep_moe`: Enables expert parallelism that distributes the experts onto multiple GPUs for DeepSeek-V3 model based on deepseek-ai/DeepEP.
 
 ## Memory and scheduling
 
@@ -184,7 +184,7 @@ Please consult the documentation below to learn more about the parameters you ma
 *Note: Some of these options are still in experimental stage.*
 
 * `enable_mixed_chunk`: Enables mixing prefill and decode, see [this discussion](https://github.com/sgl-project/sglang/discussions/1163).
-* `enable_dp_attention`: Enable [Data Parallelism Attention](https://lmsys.org/blog/2024-12-04-sglang-v0-4/#data-parallelism-attention-for-deepseek-models) for Deepseek models. Note that you need to choose `dp_size = tp_size` for this.
+* `enable_dp_attention`: Enable [Data Parallelism Attention](https://lmsys.org/blog/2024-12-04-sglang-v0-4/#data-parallelism-attention-for-deepseek-models) for Deepseek models.
 * `enable_torch_compile`: Torch compile the model. Note that compiling a model takes a long time but have a great performance boost. The compiled model can also be [cached for future use](https://docs.sglang.ai/backend/hyperparameter_tuning.html#enabling-cache-for-torch-compile).
 * `torch_compile_max_bs`: The maximum batch size when using `torch_compile`.
 * `cuda_graph_max_bs`: Adjust the maximum batchsize when using cuda graph. By default this is chosen for you based on GPU specifics.

python/sglang/srt/distributed/device_communicators/custom_all_reduce.py

@@ -5,7 +5,7 @@ import logging
 import os
 from contextlib import contextmanager
 from functools import wraps
-from typing import Callable, List, Optional, TypeVar, Union
+from typing import Any, Callable, List, Optional, TypeVar, Union
 
 import torch
 import torch.distributed as dist

python/sglang/srt/distributed/parallel_state.py

@@ -439,6 +439,15 @@ class GroupCoordinator:
         else:
             torch.distributed.all_reduce(input_, group=self.device_group)
 
+    def reduce_scatter(
+        self,
+        output: torch.Tensor,
+        input_list: List[torch.Tensor],
+    ) -> None:
+        # TODO(ch-wan): support other backends
+        torch.distributed.reduce_scatter(output, input_list, group=self.device_group)
+        return output
+
     def _all_gather_into_tensor(self, output: torch.Tensor, input: torch.Tensor):
         pynccl_comm = self.pynccl_comm
         if pynccl_comm is not None and not pynccl_comm.disabled:
@@ -456,11 +465,23 @@ class GroupCoordinator:
                 output, input, group_name=self.unique_name
             )
 
-    def all_gather(self, input_: torch.Tensor, dim: int = -1) -> torch.Tensor:
+    def all_gather(
+        self,
+        input_: torch.Tensor,
+        dim: int = -1,
+        tensor_list: List[torch.Tensor] = None,
+    ) -> torch.Tensor:
         world_size = self.world_size
         # Bypass the function if we are using only 1 GPU.
         if world_size == 1:
             return input_
+
+        if tensor_list is not None:
+            # TODO(ch-wan): support other backends
+            return torch.distributed.all_gather(
+                tensor_list, input_, group=self.device_group
+            )
+
         assert (
             -input_.dim() <= dim < input_.dim()
         ), f"Invalid dim ({dim}) for input tensor with shape {input_.size()}"

python/sglang/srt/layers/dp_attention.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import functools
 import logging
 from contextlib import contextmanager
-from typing import TYPE_CHECKING, Union
+from typing import TYPE_CHECKING, List
 
 import torch
 import triton
@@ -249,3 +249,14 @@ def dp_scatter(
         memcpy_triton(
             local_tokens, global_tokens, 0, local_start_pos, local_num_tokens, True
         )
+
+
+def tp_reduce_scatter(
+    output: torch.Tensor,
+    input_list: List[torch.Tensor],
+):
+    return get_attention_tp_group().reduce_scatter(output, input_list)
+
+
+def tp_all_gather(output_list: List[torch.Tensor], input_: torch.Tensor):
+    return get_attention_tp_group().all_gather(input_, tensor_list=output_list)

python/sglang/srt/managers/scheduler.py

@@ -1186,7 +1186,7 @@ class Scheduler(
                 ret = None
 
         # Handle DP attention
-        if self.server_args.enable_dp_attention:
+        if self.server_args.enable_dp_attention or self.server_args.enable_sp_layernorm:
             ret, _ = self.prepare_dp_attn_batch(ret)
 
         return ret

python/sglang/srt/model_executor/cuda_graph_runner.py

@@ -174,6 +174,7 @@ class CudaGraphRunner:
         self.disable_padding = model_runner.server_args.disable_cuda_graph_padding
         self.is_encoder_decoder = model_runner.model_config.is_encoder_decoder
         self.enable_dp_attention = model_runner.server_args.enable_dp_attention
+        self.enable_sp_layernorm = model_runner.server_args.enable_sp_layernorm
         self.speculative_algorithm = model_runner.server_args.speculative_algorithm
         self.tp_size = model_runner.server_args.tp_size
         self.dp_size = model_runner.server_args.dp_size
@@ -245,8 +246,8 @@ class CudaGraphRunner:
                 )
             else:
                 self.encoder_lens = None
-
-            if self.enable_dp_attention:
+            if self.enable_dp_attention or self.enable_sp_layernorm:
+                # TODO(ch-wan): SP layernorm should use a different logic to manage gathered_buffer
                 self.gathered_buffer = torch.zeros(
                     (
                         self.max_bs * self.dp_size * self.num_tokens_per_bs,
@@ -288,7 +289,7 @@ class CudaGraphRunner:
             self.model_runner.token_to_kv_pool.capture_mode = False
 
     def can_run(self, forward_batch: ForwardBatch):
-        if self.enable_dp_attention:
+        if self.enable_dp_attention or self.enable_sp_layernorm:
             total_global_tokens = sum(forward_batch.global_num_tokens_cpu)
 
             is_bs_supported = forward_batch.can_run_dp_cuda_graph and (
@@ -369,7 +370,7 @@ class CudaGraphRunner:
             encoder_lens = None
         mrope_positions = self.mrope_positions[:, :bs]
 
-        if self.enable_dp_attention:
+        if self.enable_dp_attention or self.enable_sp_layernorm:
             self.global_num_tokens_gpu.copy_(
                 torch.tensor(
                     [
@@ -471,7 +472,7 @@ class CudaGraphRunner:
         raw_num_token = raw_bs * self.num_tokens_per_bs
 
         # Pad
-        if self.enable_dp_attention:
+        if self.enable_dp_attention or self.enable_sp_layernorm:
             index = bisect.bisect_left(
                 self.capture_bs, sum(forward_batch.global_num_tokens_cpu)
             )
@@ -497,7 +498,7 @@ class CudaGraphRunner:
             self.encoder_lens[:raw_bs].copy_(forward_batch.encoder_lens)
         if forward_batch.mrope_positions is not None:
             self.mrope_positions[:, :raw_bs].copy_(forward_batch.mrope_positions)
-        if self.enable_dp_attention:
+        if self.enable_dp_attention or self.enable_sp_layernorm:
             self.global_num_tokens_gpu.copy_(forward_batch.global_num_tokens_gpu)
 
         if hasattr(forward_batch.spec_info, "hidden_states"):

python/sglang/srt/model_executor/model_runner.py

@@ -281,9 +281,6 @@ class ModelRunner:
 
         if server_args.enable_deepep_moe:
             logger.info("DeepEP is turned on.")
-            assert (
-                server_args.enable_dp_attention == True
-            ), "Currently DeepEP is bind to Attention DP. Set '--enable-dp-attention --enable-deepep-moe'"
 
     def init_torch_distributed(self):
         logger.info("Init torch distributed begin.")

python/sglang/srt/models/deepseek_v2.py

@@ -39,6 +39,8 @@ from sglang.srt.layers.dp_attention import (
     get_attention_dp_size,
     get_attention_tp_rank,
     get_attention_tp_size,
+    tp_all_gather,
+    tp_reduce_scatter,
 )
 from sglang.srt.layers.layernorm import RMSNorm
 from sglang.srt.layers.linear import (
@@ -278,7 +280,11 @@ class DeepseekV2MoE(nn.Module):
         topk_weights = torch.empty(
             (0, self.top_k), dtype=torch.float32, device=hidden_states.device
         )
-        if forward_mode is not None and not forward_mode.is_idle():
+        if (
+            forward_mode is not None
+            and not forward_mode.is_idle()
+            and hidden_states.shape[0] > 0
+        ):
             # router_logits: (num_tokens, n_experts)
             router_logits = self.gate(hidden_states)
             if self.n_shared_experts is not None:
@@ -969,6 +975,14 @@ class DeepseekV2DecoderLayer(nn.Module):
         is_nextn: bool = False,
         prefix: str = "",
     ) -> None:
+
+        def is_sparse_layer(l: int):
+            return (
+                config.n_routed_experts is not None
+                and l >= config.first_k_dense_replace
+                and l % config.moe_layer_freq == 0
+            )
+
         super().__init__()
         self.hidden_size = config.hidden_size
         rope_theta = getattr(config, "rope_theta", 10000)
@@ -977,6 +991,8 @@ class DeepseekV2DecoderLayer(nn.Module):
         self.enable_dp_attention = global_server_args_dict["enable_dp_attention"]
         self.layer_id = layer_id
         self.dp_size = get_attention_dp_size()
+        self.attn_tp_size = get_attention_tp_size()
+        self.attn_tp_rank = get_attention_tp_rank()
 
         if not global_server_args_dict["disable_mla"]:
             self.self_attn = DeepseekV2AttentionMLA(
@@ -1019,16 +1035,13 @@ class DeepseekV2DecoderLayer(nn.Module):
                 prefix=add_prefix("self_attn", prefix),
             )
 
-        if is_nextn or (
-            config.n_routed_experts is not None
-            and layer_id >= config.first_k_dense_replace
-            and layer_id % config.moe_layer_freq == 0
-        ):
+        if is_nextn or is_sparse_layer(layer_id):
             self.mlp = DeepseekV2MoE(
                 config=config,
                 quant_config=quant_config,
                 prefix=add_prefix("mlp", prefix),
             )
+            self.is_sparse = True
         else:
             self.mlp = DeepseekV2MLP(
                 hidden_size=config.hidden_size,
@@ -1037,6 +1050,14 @@ class DeepseekV2DecoderLayer(nn.Module):
                 quant_config=quant_config,
                 prefix=add_prefix("mlp", prefix),
             )
+            self.is_sparse = False
+
+        self.input_is_scattered = (
+            is_sparse_layer(layer_id - 1)
+            and global_server_args_dict["enable_deepep_moe"]
+        )
+        self.is_last_layer = self.layer_id == config.num_hidden_layers - 1
+
         self.input_layernorm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)
         self.post_attention_layernorm = RMSNorm(
             config.hidden_size, eps=config.rms_norm_eps
@@ -1049,6 +1070,23 @@ class DeepseekV2DecoderLayer(nn.Module):
         forward_batch: ForwardBatch,
         residual: Optional[torch.Tensor],
     ) -> torch.Tensor:
+        if global_server_args_dict["enable_deepep_moe"] and self.is_sparse:
+            return self.forward_deepep(
+                positions, hidden_states, forward_batch, residual
+            )
+        else:
+            return self.forward_normal(
+                positions, hidden_states, forward_batch, residual
+            )
+
+    def forward_normal(
+        self,
+        positions: torch.Tensor,
+        hidden_states: torch.Tensor,
+        forward_batch: ForwardBatch,
+        residual: Optional[torch.Tensor],
+    ) -> torch.Tensor:
+
         if hidden_states.shape[0] == 0:
             residual = hidden_states
         else:
@@ -1065,21 +1103,27 @@ class DeepseekV2DecoderLayer(nn.Module):
                 forward_batch=forward_batch,
             )
 
+        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,
+            )
+            tp_all_gather(
+                list(hidden_states.tensor_split(self.attn_tp_size)), local_hidden_states
+            )
+            residual, local_residual = (
+                forward_batch.gathered_buffer[: forward_batch.input_ids.shape[0]],
+                residual,
+            )
+            tp_all_gather(
+                list(residual.tensor_split(self.attn_tp_size)), local_residual
+            )
+
         # Gather
         if get_tensor_model_parallel_world_size() > 1:
             # all gather and all reduce
             if self.dp_size != 1:
-                if global_server_args_dict["enable_deepep_moe"] and isinstance(
-                    self.mlp, DeepseekV2MoE
-                ):
-                    if hidden_states.shape[0] != 0:
-                        hidden_states, residual = self.post_attention_layernorm(
-                            hidden_states, residual
-                        )
-                    hidden_states = self.mlp(hidden_states, forward_batch.forward_mode)
-                    return hidden_states, residual
-                else:
-                    if get_attention_tp_rank() == 0:
+                if self.attn_tp_rank == 0:
                     hidden_states += residual
                 hidden_states, local_hidden_states = (
                     forward_batch.gathered_buffer,
@@ -1101,6 +1145,7 @@ class DeepseekV2DecoderLayer(nn.Module):
         # Fully Connected
         hidden_states = self.mlp(hidden_states)
 
+        # TODO(ch-wan): ues reduce-scatter in MLP to avoid this scatter
         # Scatter
         if self.dp_size != 1:
             # important: forward batch.gathered_buffer is used both after scatter and after gather.
@@ -1113,6 +1158,82 @@ class DeepseekV2DecoderLayer(nn.Module):
 
         return hidden_states, residual
 
+    def forward_deepep(
+        self,
+        positions: torch.Tensor,
+        hidden_states: torch.Tensor,
+        forward_batch: ForwardBatch,
+        residual: Optional[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,
+            )
+            tp_all_gather(
+                list(hidden_states.tensor_split(self.attn_tp_size)), local_hidden_states
+            )
+
+        # Self Attention
+        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]
+                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]
+                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
+                )
+        hidden_states = self.mlp(hidden_states, forward_batch.forward_mode)
+
+        if self.is_last_layer and self.attn_tp_size != 1:
+            hidden_states, local_hidden_states = (
+                forward_batch.gathered_buffer[: forward_batch.input_ids.shape[0]],
+                hidden_states,
+            )
+            tp_all_gather(
+                list(hidden_states.tensor_split(self.attn_tp_size)), local_hidden_states
+            )
+            residual, local_residual = (
+                forward_batch.gathered_buffer[: forward_batch.input_ids.shape[0]],
+                residual,
+            )
+            tp_all_gather(
+                list(residual.tensor_split(self.attn_tp_size)), local_residual
+            )
+
+        return hidden_states, residual
+
 
 class DeepseekV2Model(nn.Module):
 

python/sglang/srt/server_args.py

@@ -290,11 +290,16 @@ class ServerArgs:
             logger.warning(
                 f"DP attention is enabled. The chunked prefill size is adjusted to {self.chunked_prefill_size} to avoid MoE kernel issues. "
             )
+
+        self.enable_sp_layernorm = False
         # DeepEP MoE
         if self.enable_deepep_moe:
-                self.ep_size = self.dp_size
+            self.ep_size = self.tp_size
+            self.enable_sp_layernorm = (
+                self.dp_size < self.tp_size if self.enable_dp_attention else True
+            )
             logger.info(
-                    f"DeepEP MoE is enabled. The expert parallel size is adjusted to be the same as the data parallel size[{self.dp_size}]."
+                f"DeepEP MoE is enabled. The expert parallel size is adjusted to be the same as the tensor parallel size[{self.tp_size}]."
             )
 
         # Speculative Decoding

test/srt/test_moe_deepep.py

@@ -12,7 +12,42 @@ from sglang.test.test_utils import (
 )
 
 
-class TestDeepEPMoE(CustomTestCase):
+class TestPureTP(CustomTestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.model = DEFAULT_MLA_MODEL_NAME_FOR_TEST
+        cls.base_url = DEFAULT_URL_FOR_TEST
+        cls.process = popen_launch_server(
+            cls.model,
+            cls.base_url,
+            timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+            other_args=[
+                "--trust-remote-code",
+                "--tp",
+                "2",
+                "--enable-deepep-moe",
+                "--disable-cuda-graph",
+            ],
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        kill_process_tree(cls.process.pid)
+
+    def test_mmlu(self):
+        args = SimpleNamespace(
+            base_url=self.base_url,
+            model=self.model,
+            eval_name="mmlu",
+            num_examples=64,
+            num_threads=32,
+        )
+
+        metrics = run_eval(args)
+        self.assertGreater(metrics["score"], 0.5)
+
+
+class TestDPAttn(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         cls.model = DEFAULT_MLA_MODEL_NAME_FOR_TEST