[Frontend][Bugfix] support prefill decode disaggregation on deepseek (#14824)

Signed-off-by: billishyahao <bill.he@amd.com>
Co-authored-by: Zhai Feiyue <80079571+ZhaiFeiyue@users.noreply.github.com>

examples/online_serving/disaggregated_prefill.sh

@@ -8,6 +8,9 @@ set -xe
 echo "🚧🚧 Warning: The usage of disaggregated prefill is experimental and subject to change 🚧🚧"
 sleep 1
 
+# meta-llama/Meta-Llama-3.1-8B-Instruct or deepseek-ai/DeepSeek-V2-Lite
+MODEL_NAME=${HF_MODEL_NAME:-meta-llama/Meta-Llama-3.1-8B-Instruct}
+
 # Trap the SIGINT signal (triggered by Ctrl+C)
 trap 'cleanup' INT
 
@@ -44,18 +47,20 @@ wait_for_server() {
 # You can also adjust --kv-ip and --kv-port for distributed inference.
 
 # prefilling instance, which is the KV producer
-CUDA_VISIBLE_DEVICES=0 vllm serve meta-llama/Meta-Llama-3.1-8B-Instruct \
+CUDA_VISIBLE_DEVICES=0 vllm serve $MODEL_NAME \
     --port 8100 \
     --max-model-len 100 \
     --gpu-memory-utilization 0.8 \
+    --trust-remote-code \
     --kv-transfer-config \
     '{"kv_connector":"PyNcclConnector","kv_role":"kv_producer","kv_rank":0,"kv_parallel_size":2}' &
 
 # decoding instance, which is the KV consumer
-CUDA_VISIBLE_DEVICES=1 vllm serve meta-llama/Meta-Llama-3.1-8B-Instruct \
+CUDA_VISIBLE_DEVICES=1 vllm serve $MODEL_NAME \
     --port 8200 \
     --max-model-len 100 \
     --gpu-memory-utilization 0.8 \
+    --trust-remote-code \
     --kv-transfer-config \
     '{"kv_connector":"PyNcclConnector","kv_role":"kv_consumer","kv_rank":1,"kv_parallel_size":2}' &
 
@@ -78,7 +83,7 @@ sleep 1
 output1=$(curl -X POST -s http://localhost:8000/v1/completions \
 -H "Content-Type: application/json" \
 -d '{
-"model": "meta-llama/Meta-Llama-3.1-8B-Instruct",
+"model": "'"$MODEL_NAME"'",
 "prompt": "San Francisco is a",
 "max_tokens": 10,
 "temperature": 0
@@ -87,7 +92,7 @@ output1=$(curl -X POST -s http://localhost:8000/v1/completions \
 output2=$(curl -X POST -s http://localhost:8000/v1/completions \
 -H "Content-Type: application/json" \
 -d '{
-"model": "meta-llama/Meta-Llama-3.1-8B-Instruct",
+"model": "'"$MODEL_NAME"'",
 "prompt": "Santa Clara is a",
 "max_tokens": 10,
 "temperature": 0

vllm/distributed/kv_transfer/kv_connector/simple_connector.py

@@ -12,6 +12,7 @@ from typing import TYPE_CHECKING, List, Optional, Tuple, Union
 
 import torch
 
+import vllm.envs as envs
 from vllm import _custom_ops as ops
 from vllm.config import VllmConfig
 from vllm.distributed.kv_transfer.kv_connector.base import KVConnectorBase
@@ -37,6 +38,8 @@ class SimpleConnector(KVConnectorBase):
 
         self.config = config.kv_transfer_config
         self.tp_size = config.parallel_config.tensor_parallel_size
+        self.is_deepseek_mla = config.model_config.is_deepseek_mla
+        self.use_mla_opt = not envs.VLLM_MLA_DISABLE
 
         if self.config.kv_connector == "PyNcclConnector":
             from vllm.distributed.kv_transfer.kv_pipe.pynccl_pipe import (
@@ -167,6 +170,24 @@ class SimpleConnector(KVConnectorBase):
         num_heads = int(model_config.num_key_value_heads / self.tp_size)
         hidden_size = model_config.hidden_size
         num_attention_heads = model_config.num_attention_heads
+
+        # Deepseek's MLA (Multi-head Latent Attention) uses two different
+        # kv_cache shapes based on whether VLLM_MLA_DISABLE is set to 0.
+        # When VLLM_MLA_DISABLE=0 (default), forward absorb is applied,
+        # resulting in a kv_cache shape of [num_blks, blk_size, 1,
+        # kv_lora_rank + qk_rope_head_dim].
+        # When VLLM_MLA_DISABLE=1, standard FA is used instead, leading
+        # to a kv_cache shape of [2, num_blks, blk_size,
+        # num_key_value_heads / tp, qk_nope_head_dim + qk_rope_head_dim].
+        # For more details, see vllm/attention/backends/mla/common.py.
+        if self.is_deepseek_mla and self.use_mla_opt:
+            head_size = model_config.kv_lora_rank + \
+                model_config.qk_rope_head_dim
+            num_heads = 1
+        elif self.is_deepseek_mla and not self.use_mla_opt:
+            head_size = model_config.qk_nope_head_dim + \
+                model_config.qk_rope_head_dim
+        else:
             head_size = getattr(model_config, "head_dim",
                                 int(hidden_size // num_attention_heads))
 
@@ -192,6 +213,10 @@ class SimpleConnector(KVConnectorBase):
             for layer_id in range(start_layer, end_layer):
                 kv_cache = kv_caches[layer_id - start_layer]
 
+                if self.is_deepseek_mla and self.use_mla_opt:
+                    key_cache = kv_cache.reshape(-1, num_heads, head_size)
+                    value_cache = kv_cache.reshape(-1, num_heads, head_size)
+                else:
                     key_cache = kv_cache[0].reshape(-1, num_heads, head_size)
                     value_cache = kv_cache[1].reshape(-1, num_heads, head_size)
 
@@ -223,6 +248,8 @@ class SimpleConnector(KVConnectorBase):
         # and hidden states.
         bypass_model_exec = True
 
+        model_config = model_executable.model.config
+
         input_tokens_tensor = model_input.input_tokens
         seq_lens = model_input.attn_metadata.seq_lens
         num_prefill_tokens = model_input.attn_metadata.num_prefill_tokens
@@ -291,6 +318,22 @@ class SimpleConnector(KVConnectorBase):
                 kv_cache = kv_caches[i - model_executable.model.start_layer]
                 layer = model_executable.model.layers[i]
 
+                if self.is_deepseek_mla and self.use_mla_opt:
+                    layer.self_attn.attn = layer.self_attn.mla_attn
+                    k_c_normed_k_pe = keys[
+                        i - model_executable.model.start_layer].to(
+                            kv_cache.device).squeeze(1)
+                    k_c_normed = k_c_normed_k_pe[:, :model_config.kv_lora_rank]
+                    k_pe = k_c_normed_k_pe[:, model_config.kv_lora_rank:]
+                    ops.concat_and_cache_mla(
+                        k_c_normed,
+                        k_pe,
+                        kv_cache,
+                        slot_mapping[start_pos:end_pos],
+                        layer.self_attn.attn.kv_cache_dtype,
+                        layer.self_attn.attn._k_scale,
+                    )
+                else:
                     key_cache, value_cache = kv_cache[0], kv_cache[1]
                     ops.reshape_and_cache_flash(
                         keys[i - model_executable.model.start_layer].to(

vllm/model_executor/models/deepseek_v2.py

@@ -589,6 +589,7 @@ class DeepseekV2Model(nn.Module):
         model_config = vllm_config.model_config
         cache_config = vllm_config.cache_config
         quant_config = vllm_config.quant_config
+        self.config = config
 
         self.vocab_size = config.vocab_size