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2026-01-09 13:34:11 +08:00
"""A GPU worker class."""
import gc
import os
from typing import Any, Dict, List, Optional, Set, Tuple
import torch
import torch_musa
import torch.distributed
from vllm.config import (CacheConfig, DeviceConfig, LoadConfig, LoRAConfig,
ModelConfig, ParallelConfig, SchedulerConfig,
VisionLanguageConfig)
from vllm.distributed import (broadcast_tensor_dict,
ensure_model_parallel_initialized,
get_tensor_model_parallel_cpu_group,
init_distributed_environment)
from vllm.distributed.device_communicators import pymccl_utils
from vllm.distributed.device_communicators.custom_all_reduce import (
init_custom_ar)
from vllm.lora.request import LoRARequest
from vllm.model_executor import set_random_seed
from vllm.sequence import ExecuteModelRequest, SamplerOutput
from vllm.worker.cache_engine import CacheEngine
from vllm.worker.model_runner import ModelRunner
from vllm.worker.worker_base import WorkerBase
class Worker(WorkerBase):
"""A worker class that executes (a partition of) the model on a GPU.
Each worker is associated with a single GPU. The worker is responsible for
maintaining the KV cache and executing the model on the GPU. In case of
distributed inference, each worker is assigned a partition of the model.
"""
def __init__(
self,
model_config: ModelConfig,
parallel_config: ParallelConfig,
scheduler_config: SchedulerConfig,
device_config: DeviceConfig,
cache_config: CacheConfig,
load_config: LoadConfig,
local_rank: int,
rank: int,
distributed_init_method: str,
lora_config: Optional[LoRAConfig] = None,
vision_language_config: Optional[VisionLanguageConfig] = None,
is_driver_worker: bool = False,
) -> None:
self.model_config = model_config
self.parallel_config = parallel_config
self.scheduler_config = scheduler_config
self.device_config = device_config
self.cache_config = cache_config
self.local_rank = local_rank
self.rank = rank
self.distributed_init_method = distributed_init_method
self.lora_config = lora_config
self.load_config = load_config
self.is_driver_worker = is_driver_worker
if self.is_driver_worker:
assert self.rank == 0, "The driver worker must have rank 0."
if self.model_config.trust_remote_code:
# note: lazy import to avoid importing torch before initializing
from vllm.utils import init_cached_hf_modules
init_cached_hf_modules()
self.vision_language_config = vision_language_config
if self.vision_language_config:
assert not self.lora_config, (
"To be tested: vision language model with LoRA settings.")
self.model_runner = ModelRunner(
model_config,
parallel_config,
scheduler_config,
device_config,
load_config=load_config,
lora_config=self.lora_config,
kv_cache_dtype=self.cache_config.cache_dtype,
is_driver_worker=is_driver_worker,
vision_language_config=vision_language_config,
)
# Uninitialized cache engine. Will be initialized by
# initialize_cache.
self.cache_engine: CacheEngine
self.gpu_cache: List[torch.Tensor]
def init_device(self) -> None:
if self.device_config.device.type == "cuda":
# torch.distributed.all_reduce does not free the input tensor until
# the synchronization point. This causes the memory usage to grow
# as the number of all_reduce calls increases. This env var disables
# this behavior.
# Related issue:
# https://discuss.pytorch.org/t/cuda-allocation-lifetime-for-inputs-to-distributed-all-reduce/191573
os.environ["TORCH_NCCL_AVOID_RECORD_STREAMS"] = "1"
# This env var set by Ray causes exceptions with graph building.
os.environ.pop("NCCL_ASYNC_ERROR_HANDLING", None)
self.device = torch.device(f"cuda:{self.local_rank}")
torch.cuda.set_device(self.device)
_check_if_gpu_supports_dtype(self.model_config.dtype)
torch.cuda.empty_cache()
self.init_gpu_memory = torch.cuda.mem_get_info()[0]
elif self.device_config.device.type == "musa":
os.environ["TORCH_NCCL_AVOID_RECORD_STREAMS"] = "1"
os.environ["TORCH_MCCL_AVOID_RECORD_STREAMS"] = "1"
# This env var set by Ray causes exceptions with graph building.
os.environ.pop("NCCL_ASYNC_ERROR_HANDLING", None)
os.environ.pop("MCCL_ASYNC_ERROR_HANDLING", None)
self.device = torch.device(f"musa:{self.local_rank}")
torch.musa.set_device(self.device)
_check_if_gpu_supports_dtype(self.model_config.dtype)
torch.musa.empty_cache()
self.init_gpu_memory = torch.musa.mem_get_info()[0]
else:
raise RuntimeError(
f"Not support device type: {self.device_config.device}")
# Initialize the distributed environment.
init_worker_distributed_environment(self.parallel_config, self.rank,
self.distributed_init_method,
self.local_rank,
backend="mccl")
# Set random seed.
set_random_seed(self.model_config.seed)
def load_model(self):
self.model_runner.load_model()
@torch.inference_mode()
def determine_num_available_blocks(self) -> Tuple[int, int]:
"""Profiles the peak memory usage of the model to determine how many
KV blocks may be allocated without OOMs.
The engine will first conduct a profiling of the existing memory usage.
Then, it calculate the maximum possible number of GPU and CPU blocks
that can be allocated with the remaining free memory.
.. tip::
You may limit the usage of GPU memory
by adjusting the `gpu_memory_utilization` parameter.
"""
# Profile the memory usage of the model and get the maximum number of
# cache blocks that can be allocated with the remaining free memory.
torch.musa.empty_cache()
# Execute a forward pass with dummy inputs to profile the memory usage
# of the model.
self.model_runner.profile_run()
# Calculate the number of blocks that can be allocated with the
# profiled peak memory.
torch.musa.synchronize()
free_gpu_memory, total_gpu_memory = torch.musa.mem_get_info()
# NOTE(woosuk): Here we assume that the other processes using the same
# GPU did not change their memory usage during the profiling.
peak_memory = self.init_gpu_memory - free_gpu_memory
assert peak_memory > 0, (
"Error in memory profiling. This happens when the GPU memory was "
"not properly cleaned up before initializing the vLLM instance.")
cache_block_size = self.get_cache_block_size_bytes()
num_gpu_blocks = int(
(total_gpu_memory * self.cache_config.gpu_memory_utilization -
peak_memory) // cache_block_size)
num_cpu_blocks = int(self.cache_config.swap_space_bytes //
cache_block_size)
num_gpu_blocks = max(num_gpu_blocks, 0)
num_cpu_blocks = max(num_cpu_blocks, 0)
if self.model_runner.lora_manager:
self.model_runner.remove_all_loras()
gc.collect()
torch.cuda.empty_cache()
return num_gpu_blocks, num_cpu_blocks
def initialize_cache(self, num_gpu_blocks: int,
num_cpu_blocks: int) -> None:
"""Allocate GPU and CPU KV cache with the specified number of blocks.
This also warms up the model, which may record CUDA graphs.
"""
raise_if_cache_size_invalid(num_gpu_blocks,
self.cache_config.block_size,
self.model_config.max_model_len)
self.cache_config.num_gpu_blocks = num_gpu_blocks
self.cache_config.num_cpu_blocks = num_cpu_blocks
self._init_cache_engine()
self._warm_up_model()
def _init_cache_engine(self):
assert self.cache_config.num_gpu_blocks is not None
self.cache_engine = CacheEngine(self.cache_config, self.model_config,
self.parallel_config)
self.gpu_cache = self.cache_engine.gpu_cache
self.model_runner.set_block_size(self.cache_engine.block_size)
def _warm_up_model(self) -> None:
if not self.model_config.enforce_eager:
self.model_runner.capture_model(self.gpu_cache)
# Reset the seed to ensure that the random state is not affected by
# the model initialization and profiling.
set_random_seed(self.model_config.seed)
def cache_swap(
self,
blocks_to_swap_in: Dict[int, int],
blocks_to_swap_out: Dict[int, int],
blocks_to_copy: Dict[int, List[int]],
) -> None:
# Issue cache operations.
# TODO(woosuk): Profile swapping overhead and optimize if needed.
if blocks_to_swap_in:
self.cache_engine.swap_in(blocks_to_swap_in)
if blocks_to_swap_out:
self.cache_engine.swap_out(blocks_to_swap_out)
if blocks_to_copy:
self.cache_engine.copy(blocks_to_copy)
@torch.inference_mode()
def execute_model(
self,
execute_model_req: Optional[ExecuteModelRequest] = None
) -> List[SamplerOutput]:
if execute_model_req is None:
seq_group_metadata_list = None
else:
seq_group_metadata_list = execute_model_req.seq_group_metadata_list
if self.is_driver_worker:
assert seq_group_metadata_list is not None
assert execute_model_req is not None
num_seq_groups = len(seq_group_metadata_list)
blocks_to_swap_in = execute_model_req.blocks_to_swap_in
blocks_to_swap_out = execute_model_req.blocks_to_swap_out
blocks_to_copy = execute_model_req.blocks_to_copy
data: Dict[str, Any] = {
"num_seq_groups": num_seq_groups,
"blocks_to_swap_in": blocks_to_swap_in,
"blocks_to_swap_out": blocks_to_swap_out,
"blocks_to_copy": blocks_to_copy,
}
broadcast_tensor_dict(data, src=0)
else:
data = broadcast_tensor_dict(src=0)
num_seq_groups = data["num_seq_groups"]
blocks_to_swap_in = data["blocks_to_swap_in"]
blocks_to_swap_out = data["blocks_to_swap_out"]
blocks_to_copy = data["blocks_to_copy"]
self.cache_swap(blocks_to_swap_in, blocks_to_swap_out, blocks_to_copy)
# If there is no input, we don't need to execute the model.
if num_seq_groups == 0:
return []
output = self.model_runner.execute_model(seq_group_metadata_list,
self.gpu_cache)
# Worker only supports single-step execution. Wrap the output in a list
# to conform to interface.
return [output]
def add_lora(self, lora_request: LoRARequest) -> bool:
return self.model_runner.add_lora(lora_request)
def remove_lora(self, lora_id: int) -> bool:
return self.model_runner.remove_lora(lora_id)
def list_loras(self) -> Set[int]:
return self.model_runner.list_loras()
@property
def max_model_len(self) -> int:
return self.model_config.max_model_len
@property
def vocab_size(self) -> int:
return self.model_runner.vocab_size
def get_cache_block_size_bytes(self) -> int:
"""Get the size of the KV cache block size in bytes.
"""
return CacheEngine.get_cache_block_size(self.cache_config,
self.model_config,
self.parallel_config)
def init_worker_distributed_environment(
parallel_config: ParallelConfig,
rank: int,
distributed_init_method: Optional[str] = None,
local_rank: int = -1,
backend: str = "nccl",
) -> None:
"""Initialize the distributed environment."""
init_distributed_environment(parallel_config.world_size, rank,
distributed_init_method, local_rank, backend)
ensure_model_parallel_initialized(parallel_config.tensor_parallel_size,
parallel_config.pipeline_parallel_size)
if pymccl_utils.is_initialized():
pynccl_world_size = pymccl_utils.get_world_size()
if pynccl_world_size != parallel_config.world_size:
raise RuntimeError(
"pynccl is already initialized but the pynccl world "
"size does not match parallel_config.world_size "
f"({pynccl_world_size} vs. {parallel_config.world_size}).")
elif parallel_config.world_size > 1:
# NOTE(woosuk): We don't initialize pynccl process group when world size
# is 1.
# NOTE(kaichao): By default, pynccl is initialized for tp group.
pymccl_utils.init_process_group(
group=get_tensor_model_parallel_cpu_group())
# Initialize a custom fast all-reduce implementation.
if not parallel_config.disable_custom_all_reduce:
init_custom_ar()
# A small all_reduce for warmup.
if backend == "mccl":
torch.distributed.all_reduce(torch.zeros(1).musa())
if pymccl_utils.is_initialized():
pymccl_utils.all_reduce(torch.zeros(1).musa())
else:
torch.distributed.all_reduce(torch.zeros(1).cuda())
if pymccl_utils.is_initialized():
pymccl_utils.all_reduce(torch.zeros(1).cuda())
def _check_if_gpu_supports_dtype(torch_dtype: torch.dtype):
# Check if the GPU supports the dtype.
if torch_dtype == torch.bfloat16:
compute_capability = torch.cuda.get_device_capability()
if compute_capability[0] < 8:
gpu_name = torch.cuda.get_device_name()
raise ValueError(
"Bfloat16 is only supported on GPUs with compute capability "
f"of at least 8.0. Your {gpu_name} GPU has compute capability "
f"{compute_capability[0]}.{compute_capability[1]}. "
"You can use float16 instead by explicitly setting the"
"`dtype` flag in CLI, for example: --dtype=half.")
def raise_if_cache_size_invalid(num_gpu_blocks, block_size,
max_model_len) -> None:
if num_gpu_blocks <= 0:
raise ValueError("No available memory for the cache blocks. "
"Try increasing `gpu_memory_utilization` when "
"initializing the engine.")
max_seq_len = block_size * num_gpu_blocks
if max_model_len > max_seq_len:
raise ValueError(
f"The model's max seq len ({max_model_len}) "
"is larger than the maximum number of tokens that can be "
f"stored in KV cache ({max_seq_len}). Try increasing "
"`gpu_memory_utilization` or decreasing `max_model_len` when "
"initializing the engine.")