Add support for LLaMA-2 (#505)

README.md

@@ -17,6 +17,7 @@ Easy, fast, and cheap LLM serving for everyone
 ---
 
 *Latest News* 🔥
+- [2023/07] Added support for LLaMA-2! You can run and serve 7B/13B/70B LLaMA-2s on vLLM with a single command!
 - [2023/06] Serving vLLM On any Cloud with SkyPilot. Check out a 1-click [example](https://github.com/skypilot-org/skypilot/blob/master/llm/vllm) to start the vLLM demo, and the [blog post](https://blog.skypilot.co/serving-llm-24x-faster-on-the-cloud-with-vllm-and-skypilot/) for the story behind vLLM development on the clouds.
 - [2023/06] We officially released vLLM! FastChat-vLLM integration has powered [LMSYS Vicuna and Chatbot Arena](https://chat.lmsys.org) since mid-April. Check out our [blog post](https://vllm.ai).
 
@@ -46,7 +47,7 @@ vLLM seamlessly supports many Huggingface models, including the following archit
 - GPT BigCode (`bigcode/starcoder`, `bigcode/gpt_bigcode-santacoder`, etc.)
 - GPT-J (`EleutherAI/gpt-j-6b`, `nomic-ai/gpt4all-j`, etc.)
 - GPT-NeoX (`EleutherAI/gpt-neox-20b`, `databricks/dolly-v2-12b`, `stabilityai/stablelm-tuned-alpha-7b`, etc.)
-- LLaMA (`lmsys/vicuna-13b-v1.3`, `young-geng/koala`, `openlm-research/open_llama_13b`, etc.)
+- LLaMA & LLaMA-2 (`meta-llama/Llama-2-70b-hf`, `lmsys/vicuna-13b-v1.3`, `young-geng/koala`, `openlm-research/open_llama_13b`, etc.)
 - MPT (`mosaicml/mpt-7b`, `mosaicml/mpt-30b`, etc.)
 - OPT (`facebook/opt-66b`, `facebook/opt-iml-max-30b`, etc.)
 

csrc/pos_encoding_kernels.cu

@@ -7,11 +7,12 @@ template<typename scalar_t>
 __global__ void rotary_embedding_neox_kernel(
   const int64_t* __restrict__ positions,        // [num_tokens]
   scalar_t* __restrict__ query,                 // [num_tokens, num_heads, head_size]
-  scalar_t* __restrict__ key,                   // [num_tokens, num_heads, head_size]
+  scalar_t* __restrict__ key,                   // [num_tokens, num_kv_heads, head_size]
   const scalar_t* __restrict__ cos_sin_cache,   // [max_position, 2, rot_dim // 2]
   const int rot_dim,
   const int stride,
   const int num_heads,
+  const int num_kv_heads,
   const int head_size) {
   // Each thread block is responsible for one token.
   const int token_idx = blockIdx.x;
@@ -19,8 +20,8 @@ __global__ void rotary_embedding_neox_kernel(
   const scalar_t* cache_ptr = cos_sin_cache + pos * rot_dim;
 
   const int embed_dim = rot_dim / 2;
-  const int n = num_heads * embed_dim;
-  for (int i = threadIdx.x; i < n; i += blockDim.x) {
+  const int nq = num_heads * embed_dim;
+  for (int i = threadIdx.x; i < nq; i += blockDim.x) {
     const int head_idx = i / embed_dim;
     const int token_head = token_idx * stride + head_idx * head_size;
 
@@ -39,11 +40,13 @@ __global__ void rotary_embedding_neox_kernel(
     query[out_x] = q_x * cos - q_y * sin;
     query[out_y] = q_y * cos + q_x * sin;
 
+    if (head_idx < num_kv_heads) {
       const scalar_t k_x = key[token_head + x_index];
       const scalar_t k_y = key[token_head + y_index];
       key[out_x] = k_x * cos - k_y * sin;
       key[out_y] = k_y * cos + k_x * sin;
     }
+  }
 }
 
 } // namespace vllm
@@ -51,13 +54,14 @@ __global__ void rotary_embedding_neox_kernel(
 void rotary_embedding_neox(
   torch::Tensor& positions,         // [num_tokens]
   torch::Tensor& query,             // [num_tokens, num_heads * head_size]
-  torch::Tensor& key,               // [num_tokens, num_heads * head_size]
+  torch::Tensor& key,               // [num_tokens, num_kv_heads * head_size]
   int head_size,
   torch::Tensor& cos_sin_cache)     // [max_position, rot_dim]
 {
   int num_tokens = query.size(0);
   int rot_dim = cos_sin_cache.size(1);
   int num_heads = query.size(1) / head_size;
+  int num_kv_heads = key.size(1) / head_size;
   int stride = query.stride(0);
   TORCH_CHECK(stride == key.stride(0));
 
@@ -78,6 +82,7 @@ void rotary_embedding_neox(
         rot_dim,
         stride,
         num_heads,
+        num_kv_heads,
         head_size);
     });
 }

docs/source/models/supported_models.rst

@@ -30,8 +30,8 @@ Alongside each architecture, we include some popular models that use it.
     - GPT-NeoX, Pythia, OpenAssistant, Dolly V2, StableLM
     - :code:`EleutherAI/gpt-neox-20b`, :code:`EleutherAI/pythia-12b`, :code:`OpenAssistant/oasst-sft-4-pythia-12b-epoch-3.5`, :code:`databricks/dolly-v2-12b`, :code:`stabilityai/stablelm-tuned-alpha-7b`, etc.
   * - :code:`LlamaForCausalLM`
-    - LLaMA, Vicuna, Alpaca, Koala, Guanaco
-    - :code:`openlm-research/open_llama_13b`, :code:`lmsys/vicuna-13b-v1.3`, :code:`young-geng/koala`, :code:`JosephusCheung/Guanaco`, etc.
+    - LLaMA, LLaMA-2, Vicuna, Alpaca, Koala, Guanaco
+    - :code:`meta-llama/Llama-2-13b-hf`, :code:`openlm-research/open_llama_13b`, :code:`lmsys/vicuna-13b-v1.3`, :code:`young-geng/koala`, :code:`JosephusCheung/Guanaco`, etc.
   * - :code:`MPTForCausalLM`
     - MPT, MPT-Instruct, MPT-Chat, MPT-StoryWriter
     - :code:`mosaicml/mpt-7b`, :code:`mosaicml/mpt-7b-storywriter`, :code:`mosaicml/mpt-30b`, etc.

requirements.txt

@@ -4,7 +4,7 @@ ray >= 2.5.1
 sentencepiece  # Required for LLaMA tokenizer.
 numpy
 torch >= 2.0.0
-transformers >= 4.28.0  # Required for LLaMA.
+transformers >= 4.31.0  # Required for LLaMA-2.
 xformers >= 0.0.19
 fastapi
 uvicorn

vllm/config.py

@@ -100,7 +100,12 @@ class ModelConfig:
             return 1
         # For Falcon:
         if getattr(self.hf_config, "n_head_kv", None) is not None:
-            return self.hf_config.n_head_kv
+            return (self.hf_config.n_head_kv //
+                    parallel_config.tensor_parallel_size)
+        # For LLaMA-2:
+        if getattr(self.hf_config, "num_key_value_heads", None) is not None:
+            return (self.hf_config.num_key_value_heads //
+                    parallel_config.tensor_parallel_size)
         total_num_attention_heads = self.hf_config.num_attention_heads
         return total_num_attention_heads // parallel_config.tensor_parallel_size
 

vllm/model_executor/layers/attention.py

@@ -128,7 +128,8 @@ class PagedAttention(nn.Module):
             query: shape = [num_generation_tokens, num_heads, head_size]
             key_cache: shape = [num_blocks, num_kv_heads, head_size/x,
                 block_size, x]
-            value_cache: shape = [num_blocks, num_kv_heads, head_size, block_size]
+            value_cache: shape = [num_blocks, num_kv_heads, head_size,
+                block_size]
             input_metadata: metadata for paged attention.
         """
         block_size = value_cache.shape[3]
@@ -241,8 +242,9 @@ class PagedAttentionWithRoPE(PagedAttention):
         rotary_dim: int,
         max_position: int = 8192,
         base: int = 10000,
+        num_kv_heads: Optional[int] = None,
     ) -> None:
-        super().__init__(num_heads, head_size, scale)
+        super().__init__(num_heads, head_size, scale, num_kv_heads)
 
         # Create the cos and sin cache.
         inv_freq = 1.0 / (base**(torch.arange(0, rotary_dim, 2) / rotary_dim))
@@ -276,11 +278,12 @@ class PagedAttentionWithRoPE(PagedAttention):
         Args:
             positions: shape = [num_tokens]
                         query: shape = [num_tokens, num_heads * head_size]
-            key: shape = [num_tokens, num_heads * head_size]
-            value: shape = [num_tokens, num_heads * head_size]
-            key_cache: shape = [num_blocks, num_heads, head_size/x,
+            key: shape = [num_tokens, num_kv_heads * head_size]
+            value: shape = [num_tokens, num_kv_heads * head_size]
+            key_cache: shape = [num_blocks, num_kv_heads, head_size/x,
                 block_size, x]
-            value_cache: shape = [num_blocks, num_heads, head_size, block_size]
+            value_cache: shape = [num_blocks, num_kv_heads, head_size,
+                block_size]
             input_metadata: metadata for paged attention.
             cache_event: event to wait for the cache operations to finish.
 

vllm/model_executor/models/llama.py

@@ -84,21 +84,26 @@ class LlamaAttention(nn.Module):
         self,
         hidden_size: int,
         num_heads: int,
+        num_kv_heads: int,
     ):
         super().__init__()
         self.hidden_size = hidden_size
-        tensor_model_parallel_world_size = (
-            get_tensor_model_parallel_world_size())
+        tp_size = get_tensor_model_parallel_world_size()
         self.total_num_heads = num_heads
-        assert self.total_num_heads % tensor_model_parallel_world_size == 0
-        self.num_heads = (self.total_num_heads //
-                          tensor_model_parallel_world_size)
+        assert self.total_num_heads % tp_size == 0
+        self.num_heads = self.total_num_heads // tp_size
+        self.total_num_kv_heads = num_kv_heads
+        assert self.total_num_kv_heads % tp_size == 0
+        self.num_kv_heads = self.total_num_kv_heads // 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
         self.scaling = self.head_dim**-0.5
 
         self.qkv_proj = ColumnParallelLinear(
             hidden_size,
-            3 * self.total_num_heads * self.head_dim,
+            (self.total_num_heads + 2 * self.total_num_kv_heads) *
+            self.head_dim,
             bias=False,
             gather_output=False,
             perform_initialization=False,
@@ -113,7 +118,8 @@ class LlamaAttention(nn.Module):
         self.attn = PagedAttentionWithRoPE(self.num_heads,
                                            self.head_dim,
                                            self.scaling,
-                                           rotary_dim=self.head_dim)
+                                           rotary_dim=self.head_dim,
+                                           num_kv_heads=self.num_kv_heads)
 
     def forward(
         self,
@@ -124,7 +130,7 @@ class LlamaAttention(nn.Module):
         cache_event: Optional[torch.cuda.Event],
     ) -> torch.Tensor:
         qkv, _ = self.qkv_proj(hidden_states)
-        q, k, v = qkv.chunk(chunks=3, dim=-1)
+        q, k, v = qkv.split([self.q_size, self.kv_size, self.kv_size], dim=-1)
         k_cache, v_cache = kv_cache
         attn_output = self.attn(positions, q, k, v, k_cache, v_cache,
                                 input_metadata, cache_event)
@@ -140,6 +146,7 @@ class LlamaDecoderLayer(nn.Module):
         self.self_attn = LlamaAttention(
             hidden_size=self.hidden_size,
             num_heads=config.num_attention_heads,
+            num_kv_heads=config.num_key_value_heads,
         )
         self.mlp = LlamaMLP(
             hidden_size=self.hidden_size,
@@ -259,9 +266,19 @@ class LlamaForCausalLM(nn.Module):
                      model_name_or_path: str,
                      cache_dir: Optional[str] = None,
                      use_np_cache: bool = False):
-        tensor_model_parallel_world_size = (
-            get_tensor_model_parallel_world_size())
+        tp_size = get_tensor_model_parallel_world_size()
         tensor_model_parallel_rank = get_tensor_model_parallel_rank()
+        q_proj_shard_size = (self.config.hidden_size // tp_size)
+        kv_proj_shard_size = (self.config.hidden_size //
+                              self.config.num_attention_heads *
+                              self.config.num_key_value_heads // tp_size)
+        attention_weight_specs = [
+            # (weight_name, shard_size, offset)
+            ("q_proj", q_proj_shard_size, 0),
+            ("k_proj", kv_proj_shard_size, q_proj_shard_size),
+            ("v_proj", kv_proj_shard_size,
+             q_proj_shard_size + kv_proj_shard_size),
+        ]
         state_dict = self.state_dict()
 
         for name, loaded_weight in hf_model_weights_iterator(
@@ -272,8 +289,7 @@ class LlamaForCausalLM(nn.Module):
             if "embed_tokens" in name or "lm_head" in name:
                 param = state_dict[name]
                 # Consider padding in the vocab size.
-                padded_vocab_size = (param.shape[0] *
-                                     tensor_model_parallel_world_size)
+                padded_vocab_size = (param.shape[0] * tp_size)
                 num_extra_rows = padded_vocab_size - self.config.vocab_size
                 extra_rows = torch.empty(num_extra_rows,
                                          loaded_weight.shape[1])
@@ -281,18 +297,17 @@ class LlamaForCausalLM(nn.Module):
                 loaded_weight = torch.cat([loaded_weight, extra_rows], dim=0)
 
             is_attention_weight = False
-            for stride_id, att_weight_name in enumerate(
-                ["q_proj", "k_proj", "v_proj"]):
-                if att_weight_name not in name:
+            for weight_name, shard_size, offset in attention_weight_specs:
+                if weight_name not in name:
                     continue
-                param = state_dict[name.replace(att_weight_name, "qkv_proj")]
-                shard_size = param.shape[0] // 3
+                param = state_dict[name.replace(weight_name, "qkv_proj")]
+
                 loaded_weight = loaded_weight[
                     shard_size * tensor_model_parallel_rank:shard_size *
                     (tensor_model_parallel_rank + 1)]
-                param_slice = param.data[shard_size * stride_id:shard_size *
-                                         (stride_id + 1)]
+                param_slice = param.data[offset:offset + shard_size]
                 assert param_slice.shape == loaded_weight.shape
+
                 param_slice.copy_(loaded_weight)
                 is_attention_weight = True
                 break