[Feat] Support FlashMLA backend with MTP and FP8 KV cache (#6109)

Co-authored-by: Yingyi <yingyihuang2000@outlook.com>
Co-authored-by: neiltian <neiltian@tencent.com>
Co-authored-by: lukec <118525388+sleepcoo@users.noreply.github.com>
Co-authored-by: kexueyu <kexueyu@tencent.com>
Co-authored-by: vincentmeng <vincentmeng@tencent.com>
Co-authored-by: pengmeng <pengmeng@tencent.com>

docs/backend/attention_backend.md

@@ -8,6 +8,7 @@
 | **FA3**                  | ✅                | ✅                | ✅     | ✅                 | ✅ |
 | **Triton**               | ❌                | ✅                | ✅     | ❌                 | ❌ |
 | **Torch Native**         | ❌                | ❌                | ❌     | ❌                 | ❌ |
+| **FlashMLA**                  | ✅                | ✅                | ✅     | ❌                 | ❌ |
 
 
 ## User guide
@@ -30,10 +31,15 @@ python3 -m sglang.launch_server --tp 8 --model deepseek-ai/DeepSeek-V3 --trust-r
 ```bash
 python3 -m sglang.launch_server --model meta-llama/Meta-Llama-3.1-8B-Instruct --attention-backend triton
 python3 -m sglang.launch_server --tp 8 --model deepseek-ai/DeepSeek-V3 --attention-backend triton --trust-remote-code
-
 ```
 
 - Torch Native
 ```bash
 python3 -m sglang.launch_server --model meta-llama/Meta-Llama-3.1-8B-Instruct --attention-backend torch_native
 ```
+
+- FlashMLA
+```bash
+python3 -m sglang.launch_server --tp 8 --model deepseek-ai/DeepSeek-R1 --attention-backend flashmla --trust-remote-code
+python3 -m sglang.launch_server --tp 8 --model deepseek-ai/DeepSeek-R1 --attention-backend flashmla --kv-cache-dtype fp8_e4m3 --trust-remote-code
+```

docs/references/deepseek.md

@@ -158,7 +158,7 @@ Add arguments `--speculative-algorithm`, `--speculative-num-steps`, `--speculati
 python3 -m sglang.launch_server --model-path deepseek-ai/DeepSeek-V3-0324 --speculative-algorithm EAGLE --speculative-num-steps 1 --speculative-eagle-topk 1 --speculative-num-draft-tokens 2 --trust-remote-code --tp 8
 ```
 - The best configuration for `--speculative-num-steps`, `--speculative-eagle-topk` and `--speculative-num-draft-tokens` can be searched with [bench_speculative.py](https://github.com/sgl-project/sglang/blob/main/scripts/playground/bench_speculative.py) script for given batch size. The minimum configuration is `--speculative-num-steps 1 --speculative-eagle-topk 1 --speculative-num-draft-tokens 2`, which can achieve speedup for larger batch sizes.
-- FlashAttention3 and Triton backend fully supports MTP usage. For FlashInfer backend (`--attention-backend flashinfer`) with speculative decoding,`--speculative-eagle-topk` parameter should be set to `1`. MTP support for the FlashMLA backend and CutlassMLA backend is still under development.
+- FlashAttention3 FlashMLA and Triton backend fully supports MTP usage. For FlashInfer backend (`--attention-backend flashinfer`) with speculative decoding,`--speculative-eagle-topk` parameter should be set to `1`. MTP support for the CutlassMLA backend is still under development.
 - To enable DeepSeek MTP for large batch sizes (>32), there are some parameters should be changed (Reference [this discussion](https://github.com/sgl-project/sglang/issues/4543#issuecomment-2737413756)):
   - Adjust `--max-running-requests` to a larger number. The default value is `32` for MTP. For larger batch sizes, you should increase this value beyond the default value.
   - Set `--cuda-graph-bs`. It's a list of batch sizes for cuda graph capture. The default captured batch sizes for speculative decoding is set [here](https://github.com/sgl-project/sglang/blob/49420741746c8f3e80e0eb17e7d012bfaf25793a/python/sglang/srt/model_executor/cuda_graph_runner.py#L126). You can include more batch sizes into it.

python/sglang/srt/layers/attention/flashinfer_mla_backend.py

@@ -346,7 +346,6 @@ class FlashInferMLAAttnBackend(AttentionBackend):
         cache_loc = forward_batch.out_cache_loc
         logits_soft_cap = layer.logit_cap
         prefill_wrapper_paged = self.forward_metadata.prefill_wrapper
-        k_buf = forward_batch.token_to_kv_pool.get_key_buffer(layer.layer_id)
 
         # Save kv cache
         if save_kv_cache and k is not None:
@@ -381,6 +380,9 @@ class FlashInferMLAAttnBackend(AttentionBackend):
             )
         else:
             # mla paged prefill
+            k_buf = forward_batch.token_to_kv_pool.get_key_buffer(layer.layer_id).to(
+                q.dtype
+            )
             if q_rope is None:
                 qall = q.view(-1, layer.tp_q_head_num, layer.head_dim)
                 q, q_rope = (
@@ -442,7 +444,9 @@ class FlashInferMLAAttnBackend(AttentionBackend):
             q_nope = reshaped_q[:, :, : layer.v_head_dim]
             q_rope = reshaped_q[:, :, layer.v_head_dim :]
 
-        k_buffer = forward_batch.token_to_kv_pool.get_key_buffer(layer.layer_id)
+        k_buffer = forward_batch.token_to_kv_pool.get_key_buffer(layer.layer_id).to(
+            q.dtype
+        )
 
         o = q_nope.new_empty(q_nope.shape)
         # Direct call to run without the wrapper
@@ -467,7 +471,7 @@ class FlashInferMLAIndicesUpdaterDecode:
         self.qk_nope_head_dim = model_runner.model_config.qk_nope_head_dim
         self.qk_rope_head_dim = model_runner.model_config.qk_rope_head_dim
         self.scaling = model_runner.model_config.scaling
-        self.data_type = model_runner.kv_cache_dtype
+        self.data_type = model_runner.dtype
         self.attn_backend = attn_backend
 
         # Buffers and wrappers
@@ -577,7 +581,7 @@ class FlashInferMLAIndicesUpdaterPrefill:
         self.qk_rope_head_dim = model_runner.model_config.qk_rope_head_dim
         self.v_head_dim = model_runner.model_config.v_head_dim
         self.scaling = model_runner.model_config.scaling
-        self.data_type = model_runner.kv_cache_dtype
+        self.data_type = model_runner.dtype
         self.q_data_type = model_runner.dtype
         self.attn_backend = attn_backend
 

python/sglang/srt/layers/attention/flashmla_backend.py

@@ -8,7 +8,7 @@ Enable speculative sampling in FlashMLA
 """
 
 from dataclasses import dataclass
-from typing import TYPE_CHECKING, Optional, Union
+from typing import TYPE_CHECKING, Callable, Optional, Tuple, Union
 
 import torch
 import triton
@@ -30,8 +30,8 @@ if TYPE_CHECKING:
 
 # FlashMLA only supports pagesize=64
 PAGE_SIZE = 64
-# TODO The current setup is hard-coded and will be changed after integrating with MTP.
+
-Q_LEN = 1
+# FlashMLA FP8 issue: https://github.com/deepseek-ai/FlashMLA/issues/56
 
 
 @dataclass
@@ -52,7 +52,7 @@ class FlashMLADecodeMetadata:
 
 
 class FlashMLABackend(FlashInferMLAAttnBackend):
-    """Flashinfer attention kernels."""
+    """Flashmla attention kernels."""
 
     def __init__(
         self,
@@ -82,12 +82,12 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
         self.q_data_type = model_runner.dtype
         self.kv_cache_dim = self.kv_lora_rank + self.qk_rope_head_dim
 
+        self.num_draft_tokens = model_runner.server_args.speculative_num_draft_tokens
+
     def init_forward_metadata(self, forward_batch: ForwardBatch):
 
         bs = forward_batch.batch_size
-        spec_info = forward_batch.spec_info
         if forward_batch.forward_mode.is_decode_or_idle():
-            if spec_info is None:
             max_seqlen_pad = triton.cdiv(
                 forward_batch.seq_lens_cpu.max().item(), PAGE_SIZE
             )
@@ -108,7 +108,7 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
             )
             mla_metadata, num_splits = get_mla_metadata(
                 forward_batch.seq_lens.to(torch.int32),
-                    Q_LEN * self.num_q_heads,
+                self.num_q_heads,
                 1,
             )
             self.forward_metadata = FlashMLADecodeMetadata(
@@ -116,8 +116,38 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
                 num_splits,
                 block_kv_indices,
             )
-            else:
+        elif forward_batch.forward_mode.is_target_verify():
-                super().init_forward_metadata(forward_batch)
+            seq_lens_cpu = forward_batch.seq_lens_cpu + self.num_draft_tokens
+            seq_lens = forward_batch.seq_lens + self.num_draft_tokens
+
+            max_seqlen_pad = triton.cdiv(seq_lens_cpu.max().item(), PAGE_SIZE)
+            block_kv_indices = torch.full(
+                (bs, max_seqlen_pad),
+                -1,
+                dtype=torch.int32,
+                device=seq_lens.device,
+            )
+            create_flashmla_kv_indices_triton[(bs,)](
+                self.req_to_token,
+                forward_batch.req_pool_indices,
+                seq_lens,
+                None,
+                block_kv_indices,
+                self.req_to_token.stride(0),
+                max_seqlen_pad,
+            )
+            mla_metadata, num_splits = get_mla_metadata(
+                seq_lens.to(torch.int32),
+                self.num_draft_tokens * self.num_q_heads,
+                1,
+            )
+
+            # Use FlashMLADecodeMetadata which has the attributes forward_extend expects
+            self.forward_metadata = FlashMLADecodeMetadata(
+                mla_metadata,
+                num_splits,
+                block_kv_indices,
+            )
         else:
             super().init_forward_metadata(forward_batch)
 
@@ -136,9 +166,20 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
         else:
             cuda_graph_kv_indices = block_kv_indices
 
+        if self.num_draft_tokens:
             self.cuda_graph_mla_metadata, self.cuda_graph_num_splits = get_mla_metadata(
-            torch.ones(max_bs, dtype=torch.int32, device=cuda_graph_kv_indices.device),
+                torch.ones(
-            Q_LEN * self.num_q_heads,
+                    max_bs, dtype=torch.int32, device=cuda_graph_kv_indices.device
+                ),
+                self.num_draft_tokens * self.num_q_heads,
+                1,
+            )
+        else:
+            self.cuda_graph_mla_metadata, self.cuda_graph_num_splits = get_mla_metadata(
+                torch.ones(
+                    max_bs, dtype=torch.int32, device=cuda_graph_kv_indices.device
+                ),
+                self.num_q_heads,
                 1,
             )
         self.cuda_graph_kv_indices = cuda_graph_kv_indices
@@ -154,7 +195,6 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
         spec_info: Optional[SpecInfo],
     ):
         if forward_mode.is_decode_or_idle():
-            if spec_info is None:
             max_seqlen_pad = triton.cdiv(seq_lens.max().item(), PAGE_SIZE)
 
             create_flashmla_kv_indices_triton[(bs,)](
@@ -168,7 +208,7 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
             )
             mla_metadata, num_splits = get_mla_metadata(
                 seq_lens.to(torch.int32),
-                    Q_LEN * self.num_q_heads,
+                self.num_q_heads,
                 1,
             )
             self.cuda_graph_mla_metadata.copy_(mla_metadata)
@@ -178,7 +218,31 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
                 self.cuda_graph_num_splits[: bs + 1],
                 self.cuda_graph_kv_indices[:bs, :max_seqlen_pad],
             )
+        elif forward_mode.is_target_verify():
+            seq_lens = seq_lens + self.num_draft_tokens
+            max_seqlen_pad = triton.cdiv(seq_lens.max().item(), PAGE_SIZE)
 
+            create_flashmla_kv_indices_triton[(bs,)](
+                self.req_to_token,
+                req_pool_indices,
+                seq_lens,
+                None,
+                self.cuda_graph_kv_indices,
+                self.req_to_token.stride(0),
+                self.cuda_graph_kv_indices.stride(0),
+            )
+            mla_metadata, num_splits = get_mla_metadata(
+                seq_lens.to(torch.int32),
+                self.num_draft_tokens * self.num_q_heads,
+                1,
+            )
+            self.cuda_graph_mla_metadata.copy_(mla_metadata)
+            self.cuda_graph_num_splits[: bs + 1].copy_(num_splits)
+            self.forward_metadata = FlashMLADecodeMetadata(
+                self.cuda_graph_mla_metadata,
+                self.cuda_graph_num_splits[: bs + 1],
+                self.cuda_graph_kv_indices[:bs, :max_seqlen_pad],
+            )
         else:
             super().init_forward_metadata_capture_cuda_graph(
                 bs,
@@ -218,7 +282,32 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
             )
             mla_metadata, num_splits = get_mla_metadata(
                 seq_lens.to(torch.int32),
-                Q_LEN * self.num_q_heads,
+                self.num_q_heads,
+                1,
+            )
+            self.cuda_graph_mla_metadata.copy_(mla_metadata)
+            self.cuda_graph_num_splits[: bs + 1].copy_(num_splits)
+            self.forward_metadata.mla_metadata = self.cuda_graph_mla_metadata
+            self.forward_metadata.num_splits = self.cuda_graph_num_splits[: bs + 1]
+            self.forward_metadata.block_kv_indices = self.cuda_graph_kv_indices[
+                :bs, :max_seqlen_pad
+            ]
+        elif forward_mode.is_target_verify():
+            seq_lens = seq_lens[:bs] + self.num_draft_tokens
+            seq_lens_cpu = seq_lens_cpu[:bs] + self.num_draft_tokens
+            max_seqlen_pad = triton.cdiv(seq_lens_cpu.max().item(), PAGE_SIZE)
+            create_flashmla_kv_indices_triton[(bs,)](
+                self.req_to_token,
+                req_pool_indices[:bs],
+                seq_lens,
+                None,
+                self.cuda_graph_kv_indices,
+                self.req_to_token.stride(0),
+                self.cuda_graph_kv_indices.stride(0),
+            )
+            mla_metadata, num_splits = get_mla_metadata(
+                seq_lens.to(torch.int32),
+                self.num_draft_tokens * self.num_q_heads,
                 1,
             )
             self.cuda_graph_mla_metadata.copy_(mla_metadata)
@@ -228,7 +317,6 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
             self.forward_metadata.block_kv_indices = self.cuda_graph_kv_indices[
                 :bs, :max_seqlen_pad
             ]
-
         else:
             super().init_forward_metadata_replay_cuda_graph(
                 bs,
@@ -268,17 +356,191 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
         k_cache = forward_batch.token_to_kv_pool.get_key_buffer(layer.layer_id)
 
         reshape_q = q.view(bs, -1, layer.tp_q_head_num, layer.head_dim)
-
+        if self.data_type == torch.float8_e4m3fn:
+            reshape_q_fp8 = reshape_q.to(torch.float8_e4m3fn)
             o, _ = flash_mla_with_kvcache(
-            q=reshape_q,
+                q=reshape_q_fp8,
                 k_cache=k_cache.view(-1, PAGE_SIZE, 1, self.kv_cache_dim),
-            block_table=self.forward_metadata.block_kv_indices,
+                block_table=self.forward_metadata.block_kv_indices[:bs],
                 cache_seqlens=forward_batch.seq_lens.to(torch.int32),
                 head_dim_v=self.kv_lora_rank,  # TODO Retrieve from config.
                 tile_scheduler_metadata=self.forward_metadata.flashmla_metadata,
                 num_splits=self.forward_metadata.num_splits,
                 softmax_scale=layer.scaling,
-            causal=False,
+                causal=True,
+                descale_q=torch.ones((1), dtype=torch.float32, device=reshape_q.device),
+                descale_k=torch.ones((1), dtype=torch.float32, device=reshape_q.device),
             )
 
             return o.view(-1, layer.tp_q_head_num * layer.v_head_dim)
+        else:
+            # todo: need check all causal True or False?
+            o, _ = flash_mla_with_kvcache(
+                q=reshape_q,
+                k_cache=k_cache.view(-1, PAGE_SIZE, 1, self.kv_cache_dim),
+                block_table=self.forward_metadata.block_kv_indices[:bs],
+                cache_seqlens=forward_batch.seq_lens.to(torch.int32),
+                head_dim_v=self.kv_lora_rank,  # TODO Retrieve from config.
+                tile_scheduler_metadata=self.forward_metadata.flashmla_metadata,
+                num_splits=self.forward_metadata.num_splits,
+                softmax_scale=layer.scaling,
+                causal=True,
+            )
+
+            return o.view(-1, layer.tp_q_head_num * layer.v_head_dim)
+
+    def forward_extend(
+        self,
+        q: torch.Tensor,
+        k: torch.Tensor,
+        v: torch.Tensor,
+        layer: RadixAttention,
+        forward_batch: ForwardBatch,
+        save_kv_cache: bool = True,
+    ):
+        if (
+            forward_batch.forward_mode == ForwardMode.EXTEND
+            or forward_batch.forward_mode == ForwardMode.DRAFT_EXTEND
+        ):
+            return super().forward_extend(q, k, v, layer, forward_batch, save_kv_cache)
+        else:
+            cache_loc = forward_batch.out_cache_loc
+
+            if k is not None:
+                assert v is not None
+                if save_kv_cache:
+                    forward_batch.token_to_kv_pool.set_kv_buffer(layer, cache_loc, k, v)
+
+            bs = forward_batch.batch_size
+            k_cache = forward_batch.token_to_kv_pool.get_key_buffer(layer.layer_id)
+
+            reshape_q = q.view(bs, -1, layer.tp_q_head_num, layer.head_dim)
+            if self.data_type == torch.float8_e4m3fn:
+                reshape_q_fp8 = reshape_q.to(torch.float8_e4m3fn)
+                o, _ = flash_mla_with_kvcache(
+                    q=reshape_q_fp8,
+                    k_cache=k_cache.view(-1, PAGE_SIZE, 1, self.kv_cache_dim),
+                    block_table=self.forward_metadata.block_kv_indices[:bs],
+                    cache_seqlens=forward_batch.seq_lens.to(torch.int32)
+                    + self.num_draft_tokens,
+                    head_dim_v=self.kv_lora_rank,
+                    tile_scheduler_metadata=self.forward_metadata.flashmla_metadata,
+                    num_splits=self.forward_metadata.num_splits,
+                    softmax_scale=layer.scaling,
+                    causal=True,
+                    descale_q=torch.ones(
+                        (1), dtype=torch.float32, device=reshape_q.device
+                    ),
+                    descale_k=torch.ones(
+                        (1), dtype=torch.float32, device=reshape_q.device
+                    ),
+                )
+            else:
+                o, _ = flash_mla_with_kvcache(
+                    q=reshape_q,
+                    k_cache=k_cache.view(-1, PAGE_SIZE, 1, self.kv_cache_dim),
+                    block_table=self.forward_metadata.block_kv_indices[:bs],
+                    cache_seqlens=forward_batch.seq_lens.to(torch.int32)
+                    + self.num_draft_tokens,
+                    head_dim_v=self.kv_lora_rank,
+                    tile_scheduler_metadata=self.forward_metadata.flashmla_metadata,
+                    num_splits=self.forward_metadata.num_splits,
+                    softmax_scale=layer.scaling,
+                    causal=True,
+                )
+            return o.view(-1, layer.tp_q_head_num * layer.v_head_dim)
+
+
+# TODO: multi step kv indices optimization
+class FlashMLAMultiStepDraftBackend:
+    """
+    Wrap multiple flashmla attention backends as one for multiple consecutive
+    draft decoding steps.
+    """
+
+    def __init__(
+        self,
+        model_runner: ModelRunner,
+        topk: int,
+        speculative_num_steps: int,
+    ):
+        from sglang.srt.speculative.eagle_utils import generate_draft_decode_kv_indices
+
+        if topk > 1:
+            raise ValueError(
+                f"Currently FlashMLA only supports topk=1 for speculative decoding"
+            )
+        self.topk = topk
+        self.speculative_num_steps = speculative_num_steps
+        max_bs = model_runner.req_to_token_pool.size * self.topk
+        self.kv_indptr = torch.zeros(
+            (
+                self.speculative_num_steps,
+                max_bs + 1,
+            ),
+            dtype=torch.int32,
+            device=model_runner.device,
+        )
+
+        self.attn_backends = []
+        for i in range(self.speculative_num_steps):
+            self.attn_backends.append(
+                FlashMLABackend(
+                    model_runner,
+                    skip_prefill=True,
+                    kv_indptr_buf=self.kv_indptr[i],
+                    kv_last_page_len_buf=None,
+                )
+            )
+
+    def common_template(
+        self,
+        forward_batch: ForwardBatch,
+        call_fn: Callable,
+    ):
+        assert forward_batch.spec_info is not None
+
+        for i in range(self.speculative_num_steps - 1):
+            call_fn(i, forward_batch)
+
+    def init_forward_metadata(self, forward_batch: ForwardBatch):
+        def call_fn(i, forward_batch):
+            assert forward_batch.spec_info is not None
+            self.attn_backends[i].init_forward_metadata(forward_batch)
+
+        self.common_template(forward_batch, call_fn)
+
+    def init_cuda_graph_state(self, max_bs: int):
+        for i in range(self.speculative_num_steps):
+            self.attn_backends[i].init_cuda_graph_state(max_bs, block_kv_indices=None)
+
+    def init_forward_metadata_capture_cuda_graph(self, forward_batch: ForwardBatch):
+        def call_fn(i, forward_batch):
+            self.attn_backends[i].init_forward_metadata_capture_cuda_graph(
+                forward_batch.batch_size,
+                forward_batch.batch_size * self.topk,
+                forward_batch.req_pool_indices,
+                forward_batch.seq_lens,
+                encoder_lens=None,
+                forward_mode=ForwardMode.DECODE,
+                spec_info=forward_batch.spec_info,
+            )
+
+        self.common_template(forward_batch, call_fn)
+
+    def init_forward_metadata_replay_cuda_graph(
+        self, forward_batch: ForwardBatch, bs: int
+    ):
+        def call_fn(i, forward_batch):
+            self.attn_backends[i].init_forward_metadata_replay_cuda_graph(
+                bs,
+                forward_batch.req_pool_indices,
+                forward_batch.seq_lens,
+                seq_lens_sum=-1,
+                encoder_lens=None,
+                forward_mode=ForwardMode.DECODE,
+                spec_info=forward_batch.spec_info,
+                seq_lens_cpu=forward_batch.seq_lens_cpu,
+            )
+
+        self.common_template(forward_batch, call_fn)

python/sglang/srt/layers/attention/utils.py

@@ -77,8 +77,8 @@ def create_flashmla_kv_indices_triton(
         ) * PAGED_SIZE
         paged_offset_out = tl.arange(0, NUM_PAGE_PER_BLOCK) + i * NUM_PAGE_PER_BLOCK
 
-        mask = paged_offset <= num_paged * PAGED_SIZE
+        mask = paged_offset < num_paged * PAGED_SIZE
-        mask_out = paged_offset_out <= num_paged
+        mask_out = paged_offset_out < num_paged
 
         data = tl.load(
             req_to_token_ptr

python/sglang/srt/model_executor/cuda_graph_runner.py

@@ -30,6 +30,7 @@ from sglang.srt.distributed.parallel_state import GroupCoordinator, graph_captur
 from sglang.srt.layers.logits_processor import LogitsProcessorOutput
 from sglang.srt.layers.moe.fused_moe_native import fused_moe_forward_native
 from sglang.srt.layers.torchao_utils import save_gemlite_cache
+from sglang.srt.managers.schedule_batch import global_server_args_dict
 from sglang.srt.model_executor.forward_batch_info import (
     CaptureHiddenMode,
     ForwardBatch,
@@ -210,6 +211,9 @@ class CudaGraphRunner:
         # Attention backend
         self.max_bs = max(self.capture_bs)
         self.max_num_token = self.max_bs * self.num_tokens_per_bs
+        if global_server_args_dict["attention_backend"] == "flashmla":
+            self.model_runner.attn_backend.init_cuda_graph_state(self.max_bs)
+        else:
             self.model_runner.attn_backend.init_cuda_graph_state(self.max_num_token)
         self.seq_len_fill_value = (
             self.model_runner.attn_backend.get_cuda_graph_seq_len_fill_value()

python/sglang/srt/speculative/eagle_worker.py

@@ -199,6 +199,19 @@ class EAGLEWorker(TpModelWorker):
             self.draft_extend_attn_backend = None
             self.padded_static_len = self.speculative_num_steps + 1
             self.has_prefill_wrapper_verify = False
+        elif self.server_args.attention_backend == "flashmla":
+            from sglang.srt.layers.attention.flashmla_backend import (
+                FlashMLAMultiStepDraftBackend,
+            )
+
+            self.draft_attn_backend = FlashMLAMultiStepDraftBackend(
+                self.draft_model_runner,
+                self.topk,
+                self.speculative_num_steps,
+            )
+            self.draft_extend_attn_backend = None
+            self.padded_static_len = self.speculative_num_steps + 1
+            self.has_prefill_wrapper_verify = False
         else:
             raise ValueError(
                 f"EAGLE is not supported in attention backend {self.server_args.attention_backend}"

test/srt/test_flashmla.py

@@ -6,6 +6,7 @@ python3 test/srt/test_flashmla.py
 import unittest
 from types import SimpleNamespace
 
+import requests
 import torch
 
 from sglang.srt.utils import kill_process_tree
@@ -14,6 +15,7 @@ from sglang.test.test_utils import (
     DEFAULT_MODEL_NAME_FOR_TEST_MLA,
     DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
     DEFAULT_URL_FOR_TEST,
+    CustomTestCase,
     is_in_ci,
     popen_launch_server,
     run_bench_one_batch,
@@ -81,5 +83,71 @@ class TestFlashMLAAttnLatency(unittest.TestCase):
             self.assertGreater(output_throughput, 100)
 
 
+class TestFlashMLAMTP(CustomTestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.model = "lmsys/sglang-ci-dsv3-test"
+        cls.base_url = DEFAULT_URL_FOR_TEST
+        other_args = ["--trust-remote-code"]
+        if torch.cuda.is_available() and torch.version.cuda:
+            other_args.extend(
+                [
+                    "--cuda-graph-max-bs",
+                    "4",
+                    "--disable-radix",
+                    "--enable-torch-compile",
+                    "--torch-compile-max-bs",
+                    "1",
+                    "--speculative-algorithm",
+                    "EAGLE",
+                    "--speculative-draft",
+                    "lmsys/sglang-ci-dsv3-test-NextN",
+                    "--speculative-num-steps",
+                    "1",
+                    "--speculative-eagle-topk",
+                    "1",
+                    "--speculative-num-draft-tokens",
+                    "2",
+                    "--attention-backend",
+                    "flashmla",
+                ]
+            )
+        cls.process = popen_launch_server(
+            cls.model,
+            cls.base_url,
+            timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+            other_args=other_args,
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        kill_process_tree(cls.process.pid)
+
+    def test_gsm8k(self):
+        requests.get(self.base_url + "/flush_cache")
+
+        args = SimpleNamespace(
+            num_shots=5,
+            data_path=None,
+            num_questions=200,
+            max_new_tokens=512,
+            parallel=128,
+            host="http://127.0.0.1",
+            port=int(self.base_url.split(":")[-1]),
+        )
+        metrics = run_eval_few_shot_gsm8k(args)
+        print(metrics)
+
+        self.assertGreater(metrics["accuracy"], 0.60)
+
+        server_info = requests.get(self.base_url + "/get_server_info")
+        print(f"{server_info=}")
+        avg_spec_accept_length = server_info.json()["internal_states"][0][
+            "avg_spec_accept_length"
+        ]
+        print(f"{avg_spec_accept_length=}")
+        self.assertGreater(avg_spec_accept_length, 1.8)
+
+
 if __name__ == "__main__":
     unittest.main()