import pickle import torch import torch.distributed as dist from multiprocessing.synchronize import Event from multiprocessing.shared_memory import SharedMemory from nanovllm.config import Config, SparsePolicyType from nanovllm.engine.sequence import Sequence from nanovllm.models.qwen3 import Qwen3ForCausalLM from nanovllm.layers.sampler import GreedySampler from nanovllm.utils.context import set_context, get_context, reset_context from nanovllm.utils.loader import load_model from nanovllm.utils.logger import get_logger from nanovllm.kvcache import create_kvcache_manager, KVCacheManager logger = get_logger("model_runner") class ModelRunner: def __init__(self, config: Config, rank: int, event: Event | list[Event]): self.config = config hf_config = config.hf_config self.block_size = config.kvcache_block_size self.enforce_eager = config.enforce_eager self.world_size = config.tensor_parallel_size self.rank = rank self.event = event dist.init_process_group("nccl", "tcp://localhost:2333", world_size=self.world_size, rank=rank) torch.cuda.set_device(rank) default_dtype = torch.get_default_dtype() torch.set_default_dtype(hf_config.torch_dtype) torch.set_default_device("cuda") self.model = Qwen3ForCausalLM(hf_config) load_model(self.model, config.model) self.sampler = GreedySampler() # Initialize sparse_prefill_policy before warmup (will be configured in allocate_kv_cache) self.sparse_prefill_policy = None #> Disable warmup for debugging self.warmup_model() self.allocate_kv_cache() if not self.enforce_eager: self.capture_cudagraph() torch.set_default_device("cpu") torch.set_default_dtype(default_dtype) if self.world_size > 1: if rank == 0: self.shm = SharedMemory(name="nanovllm", create=True, size=2**20) dist.barrier() else: dist.barrier() self.shm = SharedMemory(name="nanovllm") self.loop() def exit(self): if self.world_size > 1: self.shm.close() dist.barrier() if self.rank == 0: self.shm.unlink() if not self.enforce_eager: del self.graphs, self.graph_pool # torch.cuda.synchronize() dist.destroy_process_group() def loop(self): while True: method_name, args = self.read_shm() self.call(method_name, *args) if method_name == "exit": break def read_shm(self): assert self.world_size > 1 and self.rank > 0 self.event.wait() n = int.from_bytes(self.shm.buf[0:4], "little") method_name, *args = pickle.loads(self.shm.buf[4:n+4]) self.event.clear() return method_name, args def write_shm(self, method_name, *args): assert self.world_size > 1 and self.rank == 0 data = pickle.dumps([method_name, *args]) n = len(data) self.shm.buf[0:4] = n.to_bytes(4, "little") self.shm.buf[4:n+4] = data for event in self.event: event.set() def call(self, method_name, *args): if self.world_size > 1 and self.rank == 0: self.write_shm(method_name, *args) method = getattr(self, method_name, None) return method(*args) def warmup_model(self): torch.cuda.empty_cache() torch.cuda.reset_peak_memory_stats() # Use a reasonable warmup length instead of max_model_len # Warmup only needs to trigger CUDA kernel JIT compilation # Using 2 blocks is sufficient and avoids huge memory allocation warmup_len = min(self.block_size * 2, self.config.max_model_len) warmup_len = max(warmup_len, 128) # At least 128 tokens num_seqs = min(self.config.max_num_batched_tokens // warmup_len, self.config.max_num_seqs, 4) num_seqs = max(num_seqs, 1) seqs = [Sequence([0] * warmup_len) for _ in range(num_seqs)] self.run(seqs, True) torch.cuda.empty_cache() def allocate_kv_cache(self): config = self.config hf_config = config.hf_config free, total = torch.cuda.mem_get_info() used = total - free peak = torch.cuda.memory_stats()["allocated_bytes.all.peak"] current = torch.cuda.memory_stats()["allocated_bytes.all.current"] num_kv_heads = hf_config.num_key_value_heads // self.world_size head_dim = getattr(hf_config, "head_dim", hf_config.hidden_size // hf_config.num_attention_heads) block_bytes = 2 * hf_config.num_hidden_layers * self.block_size * num_kv_heads * head_dim * hf_config.torch_dtype.itemsize # Calculate max GPU blocks based on available memory max_gpu_blocks = int(total * config.gpu_memory_utilization - used - peak + current) // block_bytes assert max_gpu_blocks > 0 # Determine final GPU blocks: user-specified or auto (max available) if config.num_gpu_blocks > 0: num_gpu_blocks = min(config.num_gpu_blocks, max_gpu_blocks) else: num_gpu_blocks = max_gpu_blocks if config.enable_cpu_offload: # Three-region design: CPU is primary storage, GPU is working buffer # CPU blocks = all blocks needed to support max_model_len (stores complete KV for one max sequence) # GPU blocks = three-region working buffer (user-specified or auto) num_cpu_blocks = (config.max_model_len + self.block_size - 1) // self.block_size config.num_gpu_kvcache_blocks = num_gpu_blocks config.num_cpu_kvcache_blocks = num_cpu_blocks # For backward compatibility config.num_kvcache_blocks = num_gpu_blocks + num_cpu_blocks else: config.num_kvcache_blocks = num_gpu_blocks config.num_gpu_kvcache_blocks = num_gpu_blocks config.num_cpu_kvcache_blocks = 0 # Create KV cache manager using factory self.kvcache_manager: KVCacheManager = create_kvcache_manager(config) # Create sparse prefill policy for GPU-only path # This is separate from CPU offload sparse policy (which uses select_blocks) self.sparse_prefill_policy = None if not config.enable_cpu_offload and config.sparse_policy != SparsePolicyType.FULL: from nanovllm.kvcache.sparse import create_sparse_policy policy = create_sparse_policy( config.sparse_policy, vertical_size=config.minference_vertical_size, slash_size=config.minference_slash_size, adaptive_budget=config.minference_adaptive_budget, num_sink_tokens=config.minference_num_sink_tokens, num_recent_diags=config.minference_num_recent_diags, ) # Only use if policy supports sparse prefill if policy.supports_prefill: self.sparse_prefill_policy = policy logger.info(f"Sparse prefill policy enabled: {self.sparse_prefill_policy}") # Allocate cache through manager self.kvcache_manager.allocate_cache( num_layers=hf_config.num_hidden_layers, num_kv_heads=num_kv_heads, head_dim=head_dim, dtype=hf_config.torch_dtype, ) # Initialize sparse policy if manager has one (CPU offload mode) if hasattr(self.kvcache_manager, 'sparse_policy') and self.kvcache_manager.sparse_policy is not None: self.kvcache_manager.sparse_policy.initialize( num_layers=hf_config.num_hidden_layers, num_kv_heads=num_kv_heads, head_dim=head_dim, num_cpu_blocks=config.num_cpu_kvcache_blocks, dtype=hf_config.torch_dtype, device=torch.device("cuda"), ) logger.info( f"Sparse policy initialized: {config.sparse_policy.name} " f"(topk={config.sparse_topk_blocks}, threshold={config.sparse_threshold_blocks})" ) # Log KV cache allocation info with detailed per-token breakdown gpu_memory_mb = config.num_gpu_kvcache_blocks * block_bytes / (1024 ** 2) cpu_memory_mb = config.num_cpu_kvcache_blocks * block_bytes / (1024 ** 2) total_memory_mb = gpu_memory_mb + cpu_memory_mb # Calculate per-token KV cache usage # KV per token = 2 (K+V) * num_layers * kv_heads * head_dim * dtype_size dtype_size = 2 if hf_config.torch_dtype in [torch.float16, torch.bfloat16] else 4 per_token_kv_bytes = 2 * hf_config.num_hidden_layers * num_kv_heads * head_dim * dtype_size per_token_kv_kb = per_token_kv_bytes / 1024 logger.info( f"KV Cache per-token: {per_token_kv_kb:.2f}KB " f"(2 * {hf_config.num_hidden_layers}layers * {num_kv_heads}kv_heads * {head_dim}head_dim * {dtype_size}bytes)" ) logger.info( f"KV Cache per-block: {block_bytes / (1024**2):.2f}MB " f"({per_token_kv_kb:.2f}KB * {self.block_size}tokens)" ) if config.enable_cpu_offload: compute_size = config.num_gpu_kvcache_blocks // 2 tokens_per_chunk = compute_size * self.block_size logger.info( f"KV Cache allocated (Chunked Offload mode): " f"GPU={config.num_gpu_kvcache_blocks} blocks ({gpu_memory_mb:.1f}MB), " f"CPU={config.num_cpu_kvcache_blocks} blocks ({cpu_memory_mb:.1f}MB), " f"Total={total_memory_mb:.1f}MB" ) logger.info( f"Chunked Offload config: compute_size={compute_size} blocks, " f"tokens_per_chunk={tokens_per_chunk}, " f"block_size={self.block_size}" ) else: logger.info( f"KV Cache allocated: " f"GPU={config.num_gpu_kvcache_blocks} blocks ({gpu_memory_mb:.1f}MB), " f"block_size={self.block_size}" ) #> Bind layer caches to attention modules and set layer_id layer_id = 0 for module in self.model.modules(): if hasattr(module, "k_cache") and hasattr(module, "v_cache"): k_cache, v_cache = self.kvcache_manager.get_layer_cache(layer_id) module.k_cache = k_cache module.v_cache = v_cache # Set layer_id for chunked prefill support if hasattr(module, "layer_id"): module.layer_id = layer_id layer_id += 1 def prepare_block_tables(self, seqs: list[Sequence]): max_len = max(len(seq.block_table) for seq in seqs) block_tables = [seq.block_table + [-1] * (max_len - len(seq.block_table)) for seq in seqs] block_tables = torch.tensor(block_tables, dtype=torch.int32, pin_memory=True).cuda(non_blocking=True) return block_tables def prepare_prefill(self, seqs: list[Sequence], chunk_info: list[tuple] = None): """ Prepare inputs for prefill. Args: seqs: List of sequences to prefill chunk_info: Optional chunked prefill info from get_gpu_block_tables_partial(). If provided, only process blocks in the chunk. Format: [(gpu_block_ids, start_block_idx, end_block_idx), ...] """ # Check if any sequence has blocks (not warmup) has_blocks = any(seq.block_table for seq in seqs) gpu_block_tables = None if has_blocks and hasattr(self, 'kvcache_manager'): if chunk_info is None: # Standard prefill - try to get all blocks # This may fail if GPU doesn't have enough capacity self.kvcache_manager.prepare_for_attention(seqs, is_prefill=True) gpu_block_tables = self.kvcache_manager.get_gpu_block_tables(seqs) else: # Chunked prefill - use provided chunk info gpu_block_tables = [info[0] for info in chunk_info] input_ids = [] positions = [] cu_seqlens_q = [0] cu_seqlens_k = [0] max_seqlen_q = 0 max_seqlen_k = 0 slot_mapping = [] block_tables = None for seq_idx, seq in enumerate(seqs): if chunk_info is not None: # Chunked prefill: only process blocks in the chunk gpu_blocks, start_block_idx, end_block_idx = chunk_info[seq_idx] if not gpu_blocks: continue # Calculate token range for this chunk start_token = start_block_idx * self.block_size end_token = min(end_block_idx * self.block_size, len(seq)) if end_block_idx == seq.num_blocks: # Last chunk includes partial last block end_token = len(seq) # Input tokens for this chunk chunk_tokens = seq[start_token:end_token] input_ids.extend(chunk_tokens) positions.extend(list(range(start_token, end_token))) seqlen_q = end_token - start_token seqlen_k = end_token # Context includes all tokens up to this point cu_seqlens_q.append(cu_seqlens_q[-1] + seqlen_q) cu_seqlens_k.append(cu_seqlens_k[-1] + seqlen_k) max_seqlen_q = max(seqlen_q, max_seqlen_q) max_seqlen_k = max(seqlen_k, max_seqlen_k) # Slot mapping for blocks in this chunk for i, gpu_block_id in enumerate(gpu_blocks): block_idx = start_block_idx + i start = gpu_block_id * self.block_size if block_idx != seq.num_blocks - 1: end = start + self.block_size else: end = start + seq.last_block_num_tokens slot_mapping.extend(list(range(start, end))) else: # Standard prefill seqlen = len(seq) input_ids.extend(seq[seq.num_cached_tokens:]) positions.extend(list(range(seq.num_cached_tokens, seqlen))) seqlen_q = seqlen - seq.num_cached_tokens seqlen_k = seqlen cu_seqlens_q.append(cu_seqlens_q[-1] + seqlen_q) cu_seqlens_k.append(cu_seqlens_k[-1] + seqlen_k) max_seqlen_q = max(seqlen_q, max_seqlen_q) max_seqlen_k = max(seqlen_k, max_seqlen_k) if not seq.block_table: # warmup continue # Use GPU physical block IDs for slot mapping gpu_blocks = gpu_block_tables[seq_idx] for i in range(seq.num_cached_blocks, seq.num_blocks): start = gpu_blocks[i] * self.block_size if i != seq.num_blocks - 1: end = start + self.block_size else: end = start + seq.last_block_num_tokens slot_mapping.extend(list(range(start, end))) if cu_seqlens_k[-1] > cu_seqlens_q[-1] and gpu_block_tables: # prefix cache block_tables = self._prepare_gpu_block_tables(gpu_block_tables) input_ids = torch.tensor(input_ids, dtype=torch.int64, pin_memory=True).cuda(non_blocking=True) positions = torch.tensor(positions, dtype=torch.int64, pin_memory=True).cuda(non_blocking=True) cu_seqlens_q = torch.tensor(cu_seqlens_q, dtype=torch.int32, pin_memory=True).cuda(non_blocking=True) cu_seqlens_k = torch.tensor(cu_seqlens_k, dtype=torch.int32, pin_memory=True).cuda(non_blocking=True) slot_mapping = torch.tensor(slot_mapping, dtype=torch.int32, pin_memory=True).cuda(non_blocking=True) set_context(True, cu_seqlens_q, cu_seqlens_k, max_seqlen_q, max_seqlen_k, slot_mapping, None, block_tables, sparse_prefill_policy=self.sparse_prefill_policy) return input_ids, positions def prepare_decode(self, seqs: list[Sequence]): # Prepare KV cache (updates gather_indices for hybrid manager) if hasattr(self, 'kvcache_manager'): self.kvcache_manager.prepare_for_attention(seqs, is_prefill=False) # Get GPU physical block tables gpu_block_tables = self.kvcache_manager.get_gpu_block_tables(seqs) else: gpu_block_tables = [list(seq.block_table) for seq in seqs] input_ids = [] positions = [] slot_mapping = [] context_lens = [] for seq_idx, seq in enumerate(seqs): input_ids.append(seq.last_token) positions.append(len(seq) - 1) context_lens.append(len(seq)) # Use GPU physical block ID for slot mapping gpu_blocks = gpu_block_tables[seq_idx] slot_mapping.append(gpu_blocks[-1] * self.block_size + seq.last_block_num_tokens - 1) input_ids = torch.tensor(input_ids, dtype=torch.int64, pin_memory=True).cuda(non_blocking=True) positions = torch.tensor(positions, dtype=torch.int64, pin_memory=True).cuda(non_blocking=True) slot_mapping = torch.tensor(slot_mapping, dtype=torch.int32, pin_memory=True).cuda(non_blocking=True) context_lens = torch.tensor(context_lens, dtype=torch.int32, pin_memory=True).cuda(non_blocking=True) # Use GPU physical block tables for attention block_tables = self._prepare_gpu_block_tables(gpu_block_tables) set_context(False, slot_mapping=slot_mapping, context_lens=context_lens, block_tables=block_tables) return input_ids, positions def _prepare_gpu_block_tables(self, gpu_block_tables: list[list[int]]): """Prepare block tables tensor from GPU physical block IDs.""" max_len = max(len(bt) for bt in gpu_block_tables) padded = [bt + [-1] * (max_len - len(bt)) for bt in gpu_block_tables] return torch.tensor(padded, dtype=torch.int32, pin_memory=True).cuda(non_blocking=True) def prepare_sample(self, seqs: list[Sequence]): temperatures = [] for seq in seqs: temperatures.append(seq.temperature) temperatures = torch.tensor(temperatures, dtype=torch.float32, pin_memory=True).cuda(non_blocking=True) return temperatures @torch.inference_mode() def run_model(self, input_ids: torch.Tensor, positions: torch.Tensor, is_prefill: bool): context = get_context() # Use eager mode for: prefill, enforce_eager, large batch, or chunked attention # Chunked attention requires dynamic KV loading that can't be captured in CUDA Graph use_eager = is_prefill or self.enforce_eager or input_ids.size(0) > 512 or context.is_chunked_prefill if use_eager: return self.model.compute_logits(self.model(input_ids, positions)) else: bs = input_ids.size(0) context = get_context() graph = self.graphs[next(x for x in self.graph_bs if x >= bs)] graph_vars = self.graph_vars graph_vars["input_ids"][:bs] = input_ids graph_vars["positions"][:bs] = positions graph_vars["slot_mapping"].fill_(-1) graph_vars["slot_mapping"][:bs] = context.slot_mapping graph_vars["context_lens"].zero_() graph_vars["context_lens"][:bs] = context.context_lens graph_vars["block_tables"][:bs, :context.block_tables.size(1)] = context.block_tables graph.replay() return self.model.compute_logits(graph_vars["outputs"][:bs]) def run(self, seqs: list[Sequence], is_prefill: bool) -> list[int]: #> Check if Layer-wise Offload mode should be used (CPU offload enabled) if hasattr(self, 'kvcache_manager') and hasattr(self.kvcache_manager, 'offload_engine'): use_layerwise_offload = self._should_use_layerwise_offload(seqs, is_prefill) if use_layerwise_offload: if is_prefill: return self.run_layerwise_offload_prefill(seqs) else: return self.run_layerwise_offload_decode(seqs) #> Following Code will not use Layer-wise Offload mode input_ids, positions = self.prepare_prefill(seqs) if is_prefill else self.prepare_decode(seqs) temperatures = self.prepare_sample(seqs) if self.rank == 0 else None logits = self.run_model(input_ids, positions, is_prefill) token_ids = self.sampler(logits, temperatures).tolist() if self.rank == 0 else None reset_context() return token_ids def _should_use_layerwise_offload(self, seqs: list[Sequence], is_prefill: bool) -> bool: """ Check if layer-wise offload mode should be used. Use layer-wise offload when: - CPU offload is enabled (offload_engine exists) - Sequence has blocks allocated (not warmup) """ if not hasattr(self.kvcache_manager, 'offload_engine'): return False for seq in seqs: if seq.block_table: # Has blocks - use layer-wise offload return True return False # ========== Layer-wise Offload Methods ========== @torch.inference_mode() def run_layerwise_offload_prefill(self, seqs: list[Sequence]) -> list[int]: """ Run prefill with layer-wise processing and CPU offload. Key design: - Process one layer at a time (not one chunk at a time) - Each layer: full forward pass → offload KV to CPU - Full KV stays on GPU during each layer's computation - After layer completes, KV is offloaded to CPU This enables future sparse attention methods (like MInference) that need full KV context per layer for pattern estimation. """ assert len(seqs) == 1, "Layer-wise offload only supports single sequence" seq = seqs[0] offload_engine = self.kvcache_manager.offload_engine num_layers = len(self.model.model.layers) total_tokens = len(seq) logger.debug(f"[Layer-wise Prefill] Starting: {total_tokens} tokens, {num_layers} layers") # Get CPU block IDs for offload targets cpu_block_ids, logical_ids = self.kvcache_manager.get_all_cpu_blocks(seq) # Prepare inputs input_ids = torch.tensor(seq[:], dtype=torch.int64, device="cuda") positions = torch.arange(total_tokens, dtype=torch.int64, device="cuda") # Step 1: Embedding hidden_states = self.model.model.embed_tokens(input_ids) residual = None # Step 2: Layer-by-layer processing for layer_id in range(num_layers): layer = self.model.model.layers[layer_id] # 2a. Input LayerNorm if residual is None: hidden_ln, residual = layer.input_layernorm(hidden_states), hidden_states else: hidden_ln, residual = layer.input_layernorm(hidden_states, residual) # 2b. Self-attention (full sequence) # QKV projection qkv = layer.self_attn.qkv_proj(hidden_ln) q, k, v = qkv.split([ layer.self_attn.q_size, layer.self_attn.kv_size, layer.self_attn.kv_size ], dim=-1) q = q.view(total_tokens, layer.self_attn.num_heads, layer.self_attn.head_dim) k = k.view(total_tokens, layer.self_attn.num_kv_heads, layer.self_attn.head_dim) v = v.view(total_tokens, layer.self_attn.num_kv_heads, layer.self_attn.head_dim) # Q/K norms (Qwen3 specific) if not layer.self_attn.qkv_bias: num_tokens = q.shape[0] q = layer.self_attn.q_norm(q.reshape(-1, layer.self_attn.head_dim)) q = q.view(num_tokens, layer.self_attn.num_heads, layer.self_attn.head_dim) k = layer.self_attn.k_norm(k.reshape(-1, layer.self_attn.head_dim)) k = k.view(num_tokens, layer.self_attn.num_kv_heads, layer.self_attn.head_dim) # RoPE q, k = layer.self_attn.rotary_emb(positions, q, k) # Full attention using FlashAttention from flash_attn.flash_attn_interface import flash_attn_varlen_func cu_seqlens = torch.tensor([0, total_tokens], dtype=torch.int32, device="cuda") attn_output = flash_attn_varlen_func( q, k, v, cu_seqlens_q=cu_seqlens, cu_seqlens_k=cu_seqlens, max_seqlen_q=total_tokens, max_seqlen_k=total_tokens, softmax_scale=layer.self_attn.attn.scale, causal=True, ) # O projection attn_output = attn_output.view(total_tokens, -1) hidden_states = layer.self_attn.o_proj(attn_output) # 2c. Post-attention LayerNorm + MLP hidden_states, residual = layer.post_attention_layernorm(hidden_states, residual) hidden_states = layer.mlp(hidden_states) # 2d. Offload KV to CPU (synchronous for correctness) # Use synchronous copy to ensure data is fully copied before moving to next layer self._offload_layer_kv_to_cpu_sync(layer_id, k, v, cpu_block_ids, total_tokens) # Mark all blocks as prefilled for logical_id in logical_ids: self.kvcache_manager.prefilled_blocks.add(logical_id) # Sync offload completes within loop, no explicit wait needed # Step 3: Final norm hidden_states, _ = self.model.model.norm(hidden_states, residual) # Step 4: Compute logits for last token logits = self.model.compute_logits(hidden_states[-1:]) # Step 5: Sample temperatures = self.prepare_sample(seqs) if self.rank == 0 else None token_ids = self.sampler(logits, temperatures).tolist() if self.rank == 0 else None logger.debug(f"[Layer-wise Prefill] Complete: {num_layers} layers processed") return token_ids def _offload_layer_kv_to_cpu( self, layer_id: int, k: torch.Tensor, v: torch.Tensor, cpu_block_ids: list[int], total_tokens: int, ): """ Offload a layer's KV cache to CPU in blocks (async version). Args: layer_id: Layer index k: Key tensor [seq_len, kv_heads, head_dim] v: Value tensor [seq_len, kv_heads, head_dim] cpu_block_ids: List of CPU block IDs to offload to total_tokens: Total number of tokens """ offload_engine = self.kvcache_manager.offload_engine block_size = offload_engine.block_size stream = offload_engine.prefill_offload_streams[layer_id] with torch.cuda.stream(stream): for i, cpu_block_id in enumerate(cpu_block_ids): start = i * block_size end = min(start + block_size, total_tokens) actual_size = end - start # Copy K and V to CPU cache offload_engine.k_cache_cpu[layer_id, cpu_block_id, :actual_size].copy_( k[start:end], non_blocking=True ) offload_engine.v_cache_cpu[layer_id, cpu_block_id, :actual_size].copy_( v[start:end], non_blocking=True ) # Record completion event offload_engine.prefill_offload_events[layer_id].record(stream) def _offload_layer_kv_to_cpu_sync( self, layer_id: int, k: torch.Tensor, v: torch.Tensor, cpu_block_ids: list[int], total_tokens: int, ): """ Offload a layer's KV cache to CPU in blocks (synchronous version). This version uses synchronous copy to ensure correctness. It's slower than async but guarantees data integrity. """ offload_engine = self.kvcache_manager.offload_engine block_size = offload_engine.block_size for i, cpu_block_id in enumerate(cpu_block_ids): start = i * block_size end = min(start + block_size, total_tokens) actual_size = end - start # Synchronous copy to CPU offload_engine.k_cache_cpu[layer_id, cpu_block_id, :actual_size].copy_(k[start:end]) offload_engine.v_cache_cpu[layer_id, cpu_block_id, :actual_size].copy_(v[start:end]) @torch.inference_mode() def run_layerwise_offload_decode(self, seqs: list[Sequence]) -> list[int]: """ Run decode with layer-wise KV loading from CPU. Key design: - For each layer: load all prefilled KV from CPU - Compute attention with loaded KV + new token's KV - Store new token's KV for offload when block is full """ assert len(seqs) == 1, "Layer-wise offload only supports single sequence" seq = seqs[0] offload_engine = self.kvcache_manager.offload_engine num_layers = len(self.model.model.layers) # Prepare inputs input_ids = torch.tensor([seq.last_token], dtype=torch.int64, device="cuda") positions = torch.tensor([len(seq) - 1], dtype=torch.int64, device="cuda") # Get prefilled CPU blocks cpu_block_table = self.kvcache_manager.get_prefilled_cpu_blocks(seq) num_prefill_blocks = len(cpu_block_table) total_prefill_tokens = self.kvcache_manager.get_prefill_len(seq) # Calculate valid tokens in last prefill block last_block_valid_tokens = total_prefill_tokens % self.block_size if last_block_valid_tokens == 0 and total_prefill_tokens > 0: last_block_valid_tokens = self.block_size # Current decode position info pos_in_block = (len(seq) - 1) % self.block_size decode_start_pos = self.kvcache_manager.get_decode_start_pos(seq) num_decode_tokens = pos_in_block - decode_start_pos + 1 # Step 1: Embedding hidden_states = self.model.model.embed_tokens(input_ids) residual = None # Allocate buffers for new decode token's KV (per layer) # These will be accumulated and offloaded when block is full decode_k_cache = [] decode_v_cache = [] # Step 2: Layer-by-layer processing for layer_id in range(num_layers): layer = self.model.model.layers[layer_id] # 2a. Input LayerNorm if residual is None: hidden_ln, residual = layer.input_layernorm(hidden_states), hidden_states else: hidden_ln, residual = layer.input_layernorm(hidden_states, residual) # 2b. QKV projection for new token qkv = layer.self_attn.qkv_proj(hidden_ln) q, k_new, v_new = qkv.split([ layer.self_attn.q_size, layer.self_attn.kv_size, layer.self_attn.kv_size ], dim=-1) q = q.view(1, layer.self_attn.num_heads, layer.self_attn.head_dim) k_new = k_new.view(1, layer.self_attn.num_kv_heads, layer.self_attn.head_dim) v_new = v_new.view(1, layer.self_attn.num_kv_heads, layer.self_attn.head_dim) # Q/K norms if not layer.self_attn.qkv_bias: q = layer.self_attn.q_norm(q.reshape(-1, layer.self_attn.head_dim)) q = q.view(1, layer.self_attn.num_heads, layer.self_attn.head_dim) k_new = layer.self_attn.k_norm(k_new.reshape(-1, layer.self_attn.head_dim)) k_new = k_new.view(1, layer.self_attn.num_kv_heads, layer.self_attn.head_dim) # RoPE q, k_new = layer.self_attn.rotary_emb(positions, q, k_new) # Store new KV for later offload decode_k_cache.append(k_new.clone()) decode_v_cache.append(v_new.clone()) # 2c. Load prefilled KV from CPU k_prefill_list = [] v_prefill_list = [] for block_idx, cpu_block_id in enumerate(cpu_block_table): # Determine valid tokens in this block if block_idx == num_prefill_blocks - 1: valid_tokens = last_block_valid_tokens else: valid_tokens = self.block_size k_block = offload_engine.k_cache_cpu[layer_id, cpu_block_id, :valid_tokens].to("cuda", non_blocking=True) v_block = offload_engine.v_cache_cpu[layer_id, cpu_block_id, :valid_tokens].to("cuda", non_blocking=True) k_prefill_list.append(k_block) v_prefill_list.append(v_block) # Concatenate prefilled KV if k_prefill_list: k_prefill = torch.cat(k_prefill_list, dim=0) # [prefill_tokens, kv_heads, head_dim] v_prefill = torch.cat(v_prefill_list, dim=0) else: k_prefill = torch.empty(0, layer.self_attn.num_kv_heads, layer.self_attn.head_dim, device="cuda") v_prefill = torch.empty(0, layer.self_attn.num_kv_heads, layer.self_attn.head_dim, device="cuda") # 2d. Get accumulated decode KV from decode buffer (if any previous decode tokens) if num_decode_tokens > 1: # Load previous decode tokens for this layer from decode buffer k_decode_prev = offload_engine.decode_k_buffer[layer_id, decode_start_pos:pos_in_block] v_decode_prev = offload_engine.decode_v_buffer[layer_id, decode_start_pos:pos_in_block] k_full = torch.cat([k_prefill, k_decode_prev, k_new], dim=0) v_full = torch.cat([v_prefill, v_decode_prev, v_new], dim=0) else: k_full = torch.cat([k_prefill, k_new], dim=0) v_full = torch.cat([v_prefill, v_new], dim=0) # Store new KV to decode buffer for future decode steps offload_engine.decode_k_buffer[layer_id, pos_in_block].copy_(k_new.squeeze(0)) offload_engine.decode_v_buffer[layer_id, pos_in_block].copy_(v_new.squeeze(0)) # 2e. Compute attention # For decode: query is at the last position, should attend to ALL previous keys # Use causal=False because the single query token is conceptually at position N # and should attend to all K tokens at positions 0 to N-1 from flash_attn.flash_attn_interface import flash_attn_varlen_func total_kv_tokens = k_full.shape[0] cu_seqlens_q = torch.tensor([0, 1], dtype=torch.int32, device="cuda") cu_seqlens_k = torch.tensor([0, total_kv_tokens], dtype=torch.int32, device="cuda") attn_output = flash_attn_varlen_func( q, k_full, v_full, cu_seqlens_q=cu_seqlens_q, cu_seqlens_k=cu_seqlens_k, max_seqlen_q=1, max_seqlen_k=total_kv_tokens, softmax_scale=layer.self_attn.attn.scale, causal=False, ) # O projection attn_output = attn_output.view(1, -1) hidden_states = layer.self_attn.o_proj(attn_output) # 2f. Post-attention LayerNorm + MLP hidden_states, residual = layer.post_attention_layernorm(hidden_states, residual) hidden_states = layer.mlp(hidden_states) # Step 3: Final norm hidden_states, _ = self.model.model.norm(hidden_states, residual) # Step 4: Compute logits logits = self.model.compute_logits(hidden_states) # Step 5: Handle block-full offload if pos_in_block == self.block_size - 1: # Block is full, offload decode buffer to CPU last_cpu_block = self.kvcache_manager.get_last_cpu_block(seq) if last_cpu_block >= 0: for layer_id in range(num_layers): offload_engine.k_cache_cpu[layer_id, last_cpu_block].copy_( offload_engine.decode_k_buffer[layer_id], non_blocking=True ) offload_engine.v_cache_cpu[layer_id, last_cpu_block].copy_( offload_engine.decode_v_buffer[layer_id], non_blocking=True ) torch.cuda.synchronize() # Mark as prefilled for future decode steps logical_id = seq.block_table[-1] self.kvcache_manager.prefilled_blocks.add(logical_id) # Reset decode start position self.kvcache_manager.reset_decode_start_pos(seq) # Step 6: Sample temperatures = self.prepare_sample(seqs) if self.rank == 0 else None token_ids = self.sampler(logits, temperatures).tolist() if self.rank == 0 else None return token_ids @torch.inference_mode() def capture_cudagraph(self): config = self.config hf_config = config.hf_config max_bs = min(self.config.max_num_seqs, 512) max_num_blocks = (config.max_model_len + self.block_size - 1) // self.block_size input_ids = torch.zeros(max_bs, dtype=torch.int64) positions = torch.zeros(max_bs, dtype=torch.int64) slot_mapping = torch.zeros(max_bs, dtype=torch.int32) context_lens = torch.zeros(max_bs, dtype=torch.int32) block_tables = torch.zeros(max_bs, max_num_blocks, dtype=torch.int32) outputs = torch.zeros(max_bs, hf_config.hidden_size) self.graph_bs = [1, 2, 4, 8] + list(range(16, max_bs + 1, 16)) self.graphs = {} self.graph_pool = None for bs in reversed(self.graph_bs): graph = torch.cuda.CUDAGraph() set_context(False, slot_mapping=slot_mapping[:bs], context_lens=context_lens[:bs], block_tables=block_tables[:bs]) outputs[:bs] = self.model(input_ids[:bs], positions[:bs]) # warmup with torch.cuda.graph(graph, self.graph_pool): outputs[:bs] = self.model(input_ids[:bs], positions[:bs]) # capture if self.graph_pool is None: self.graph_pool = graph.pool() self.graphs[bs] = graph torch.cuda.synchronize() reset_context() self.graph_vars = dict( input_ids=input_ids, positions=positions, slot_mapping=slot_mapping, context_lens=context_lens, block_tables=block_tables, outputs=outputs, )