worker.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""A GPU worker class."""
import gc
import os
from contextlib import nullcontext
from typing import Dict, List, Optional, Set, Tuple, Type, Union

import torch
import torch.distributed

import vllm.envs as envs
from vllm.attention.layer import Attention
from vllm.config import VllmConfig, get_layers_from_vllm_config
from vllm.device_allocator.cumem import CuMemAllocator
from vllm.distributed import (ensure_model_parallel_initialized,
                              init_distributed_environment,
                              set_custom_all_reduce)
from vllm.distributed.kv_transfer import ensure_kv_transfer_initialized
from vllm.logger import init_logger
from vllm.lora.request import LoRARequest
from vllm.model_executor import set_random_seed
from vllm.model_executor.layers.sampler import SamplerOutput
from vllm.model_executor.model_loader.tensorizer import TensorizerConfig
from vllm.platforms import current_platform
from vllm.sequence import (ExecuteModelRequest, IntermediateTensors,
                           SequenceGroupMetadata, SequenceGroupMetadataDelta)
from vllm.utils import (GiB_bytes, MemorySnapshot, bind_kv_cache,
                        memory_profiling)
from vllm.worker.cache_engine import CacheEngine
from vllm.worker.enc_dec_model_runner import EncoderDecoderModelRunner
from vllm.worker.model_runner import GPUModelRunnerBase, ModelRunner
from vllm.worker.worker_base import (LocalOrDistributedWorkerBase, WorkerBase,
                                     WorkerInput)

logger = init_logger(__name__)


class Worker(LocalOrDistributedWorkerBase):
    """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,
        vllm_config: VllmConfig,
        local_rank: int,
        rank: int,
        distributed_init_method: str,
        is_driver_worker: bool = False,
        model_runner_cls: Optional[Type[GPUModelRunnerBase]] = None,
    ) -> None:
        WorkerBase.__init__(self, vllm_config)
        self.parallel_config.rank = rank
        self.local_rank = local_rank
        self.rank = rank
        self.distributed_init_method = distributed_init_method
        self.is_driver_worker = is_driver_worker
        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()

        # Return hidden states from target model if the draft model is an
        # mlp_speculator
        speculative_config = self.speculative_config
        model_config = self.model_config
        speculative_args = {} if speculative_config is None \
            or (speculative_config.draft_model_config.hf_config.model_type ==
                model_config.hf_config.model_type) \
            or (speculative_config.draft_model_config.hf_config.model_type
                not in ("medusa",
                        "mlp_speculator",
                        "eagle",
                        "deepseek_mtp",
                        "longcat_flash_mtp",
                        "glm4_moe_mtp",
                        "mimo_mtp",
                        "ernie_mtp",
                        "qwen3_next_mtp")) \
                    else {"return_hidden_states": True}

        ModelRunnerClass: Type[GPUModelRunnerBase] = ModelRunner
        if self.model_config.is_encoder_decoder:
            ModelRunnerClass = EncoderDecoderModelRunner
        self.model_runner: GPUModelRunnerBase = ModelRunnerClass(
            vllm_config=self.vllm_config,
            kv_cache_dtype=self.cache_config.cache_dtype,
            is_driver_worker=is_driver_worker,
            **speculative_args,
        )
        if model_runner_cls is not None:
            self.model_runner = model_runner_cls(self.model_runner)

        # Uninitialized cache engine. Will be initialized by
        # initialize_cache.
        self.cache_engine: List[CacheEngine]
        self.gpu_cache: Optional[List[List[torch.Tensor]]] = None
        self._seq_group_metadata_cache: Dict[str, SequenceGroupMetadata] = {}

        # Buffers saved before sleep
        self._sleep_saved_buffers: Dict[str, torch.Tensor] = {}

        # Torch profiler. Enabled and configured through env vars:
        # VLLM_TORCH_PROFILER_DIR=/path/to/save/trace
        if envs.VLLM_TORCH_PROFILER_DIR:
            torch_profiler_trace_dir = envs.VLLM_TORCH_PROFILER_DIR
            logger.info("Profiling enabled. Traces will be saved to: %s",
                        torch_profiler_trace_dir)
            self.profiler = torch.profiler.profile(
                activities=[
                    torch.profiler.ProfilerActivity.CPU,
                    torch.profiler.ProfilerActivity.CUDA,
                ],
                with_stack=True,
                on_trace_ready=torch.profiler.tensorboard_trace_handler(
                    torch_profiler_trace_dir, use_gzip=True))
        else:
            self.profiler = None

    def start_profile(self):
        if self.profiler is None:
            raise RuntimeError("Profiler is not enabled.")
        self.profiler.start()

    def stop_profile(self):
        if self.profiler is None:
            raise RuntimeError("Profiler is not enabled.")
        self.profiler.stop()
        # only print profiler results on rank 0
        if self.local_rank == 0:
            print(self.profiler.key_averages().table(
                sort_by="self_cuda_time_total"))

    def sleep(self, level: int = 1) -> None:
        free_bytes_before_sleep = torch.cuda.mem_get_info()[0]

        # Save the buffers before level 2 sleep
        if level == 2:
            model = self.model_runner.model
            self._sleep_saved_buffers = {
                name: buffer.cpu().clone()
                for name, buffer in model.named_buffers()
            }

        allocator = CuMemAllocator.get_instance()
        allocator.sleep(offload_tags=("weights", ) if level == 1 else tuple())
        free_bytes_after_sleep, total = torch.cuda.mem_get_info()
        freed_bytes = free_bytes_after_sleep - free_bytes_before_sleep
        used_bytes = total - free_bytes_after_sleep
        assert freed_bytes >= 0, "Memory usage increased after sleeping."
        logger.info(
            "Sleep mode freed %.2f GiB memory, "
            "%.2f GiB memory is still in use.", freed_bytes / GiB_bytes,
            used_bytes / GiB_bytes)

    def wake_up(self, tags: Optional[list[str]] = None) -> None:
        allocator = CuMemAllocator.get_instance()
        allocator.wake_up(tags=tags)

        # Restore the buffers after level 2 sleep
        if len(self._sleep_saved_buffers):
            model = self.model_runner.model
            for name, buffer in model.named_buffers():
                if name in self._sleep_saved_buffers:
                    buffer.data.copy_(self._sleep_saved_buffers[name].data)
            self._sleep_saved_buffers = {}

    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)
            gc.collect()
            torch.cuda.empty_cache()
            torch.cuda.reset_peak_memory_stats()
            self.baseline_snapshot = MemorySnapshot()
        else:
            raise RuntimeError(
                f"Not support device type: {self.device_config.device}")
        # Initialize the distributed environment.
        init_worker_distributed_environment(self.vllm_config, self.rank,
                                            self.distributed_init_method,
                                            self.local_rank)
        # Set random seed.
        set_random_seed(self.model_config.seed)

    def load_model(self):
        if self.vllm_config.model_config.enable_sleep_mode:
            allocator = CuMemAllocator.get_instance()
            assert allocator.get_current_usage() == 0, (
                "Sleep mode can only be "
                "used for one instance per process.")
            context = allocator.use_memory_pool(tag="weights")
        else:
            context = nullcontext()
        with context:
            self.model_runner.load_model()

    def save_sharded_state(
        self,
        path: str,
        pattern: Optional[str] = None,
        max_size: Optional[int] = None,
    ) -> None:
        self.model_runner.save_sharded_state(
            path,
            pattern=pattern,
            max_size=max_size,
        )

    def save_tensorized_model(
        self,
        tensorizer_config: TensorizerConfig,
    ) -> None:
        self.model_runner.save_tensorized_model(
            tensorizer_config=tensorizer_config, )

    @torch.inference_mode()
    def determine_available_kv_cache_memory(self,
                                            total_gpu_memory: int) -> float:
        if kv_cache_memory_bytes := self.cache_config.kv_cache_memory_bytes:
            # still need a profile run which compiles the model for
            # max_num_batched_tokens
            self.model_runner.profile_run()

            GiB = lambda b: b / GiB_bytes
            msg = (
                f"Initial free memory "
                f"{GiB(self.baseline_snapshot.free_memory):.2f} "
                f"GiB, reserved {GiB(kv_cache_memory_bytes):.2f}GiB memory for "
                "KV Cache as specified by kv_cache_memory_bytes config and "
                "skipped memory profiling. This does does not respect the "
                "gpu_memory_utilization config. Only use kv_cache_memory_bytes "
                "config when you want manual control of KV cache memory "
                "size. If OOM'ed, check the difference of initial free "
                "memory between the current run and the previous run "
                "where kv_cache_memory_bytes is suggested and update it "
                "correspondingly.")
            logger.info(msg)
            return self.cache_config.kv_cache_memory_bytes

        # Execute a forward pass with dummy inputs to profile the memory usage
        # of the model.
        with memory_profiling(
                self.baseline_snapshot,
                weights_memory=self.model_runner.model_memory_usage) as result:
            self.model_runner.profile_run()

        self.non_torch_memory = result.non_torch_increase
        self.peak_activation_memory = result.torch_peak_increase

        self._assert_memory_footprint_increased_during_profiling()

        self.requested_memory = total_gpu_memory * \
            self.cache_config.gpu_memory_utilization

        self.available_kv_cache_memory = (self.requested_memory -
                                          result.non_kv_cache_memory)

        msg = (f"Memory profiling takes {result.profile_time:.2f} seconds\n"
               "the current vLLM instance can use "
               "total_gpu_memory "
               f"({(total_gpu_memory / GiB_bytes):.2f}GiB)"
               " x gpu_memory_utilization "
               f"({self.cache_config.gpu_memory_utilization:.2f})"
               f" = {(self.requested_memory / GiB_bytes):.2f}GiB\n"
               "model weights take "
               f"{(result.weights_memory / GiB_bytes):.2f}GiB;"
               " non_torch_memory takes "
               f"{(result.non_torch_increase / GiB_bytes):.2f}GiB;"
               " PyTorch activation peak memory takes "
               f"{(result.torch_peak_increase / GiB_bytes):.2f}GiB;"
               " the rest of the memory reserved for KV Cache is "
               f"{(self.available_kv_cache_memory / GiB_bytes):.2f}GiB.")

        logger.info(msg)
        return self.available_kv_cache_memory

    @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 calculates 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.cuda.empty_cache()
        torch.cuda.reset_peak_memory_stats()

        free_memory_pre_profile, total_gpu_memory = torch.cuda.mem_get_info()
        available_kv_cache_memory = self.determine_available_kv_cache_memory(
            total_gpu_memory)

        # Calculate the number of blocks that can be allocated with the
        # profiled peak memory.
        cache_block_size = self.get_cache_block_size_bytes()
        if cache_block_size == 0:
            num_gpu_blocks = 0
            num_cpu_blocks = 0
        else:
            num_gpu_blocks = int(available_kv_cache_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)

        # Final cleanup
        gc.collect()

        return num_gpu_blocks, num_cpu_blocks

    def _assert_memory_footprint_increased_during_profiling(self):
        # NOTE(woosuk): Here we assume that the other processes using the same
        # GPU did not change their memory usage during the profiling.
        free_gpu_memory, total = torch.cuda.mem_get_info()
        cuda_memory = total - free_gpu_memory
        assert self.baseline_snapshot.cuda_memory < cuda_memory, (
            "Error in memory profiling. "
            f"Initial used memory {self.baseline_snapshot.cuda_memory}, "
            f"currently used memory {cuda_memory}. "
            f"This happens when the GPU memory was "
            "not properly cleaned up before initializing the vLLM instance.")

    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.cache_config.is_attention_free,
            self.model_config.max_model_len,
            self.parallel_config.pipeline_parallel_size)

        self.cache_config.num_gpu_blocks = num_gpu_blocks
        self.cache_config.num_cpu_blocks = num_cpu_blocks

        if self.vllm_config.model_config.enable_sleep_mode:
            allocator = CuMemAllocator.get_instance()
            context = allocator.use_memory_pool(tag="kv_cache")
        else:
            context = nullcontext()
        with context:
            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.device_config)
            for _ in range(self.parallel_config.pipeline_parallel_size)
        ]
        self.gpu_cache = [
            self.cache_engine[ve].gpu_cache
            for ve in range(self.parallel_config.pipeline_parallel_size)
        ]

        # Layer pairings for cross-layer KV sharing.
        # If an Attention layer `layer_name` is in the keys of this dict, it
        # means this layer will perform attention using the keys and values
        # from the KV cache of `shared_kv_cache_layers[layer_name]`.
        shared_kv_cache_layers: dict[str, str] = {}

        attn_layers = get_layers_from_vllm_config(self.vllm_config, Attention)

        for layer_name, attn_module in attn_layers.items():
            if (kv_tgt_layer :=
                    attn_module.kv_sharing_target_layer_name) is not None:
                # The layer doesn't need its own KV cache and will use that of
                # the target layer. We skip creating a KVCacheSpec for it, so
                # that KV cache management logic will act as this layer does
                # not exist, and doesn't allocate KV cache for the layer. This
                # enables the memory saving of cross-layer kv sharing, allowing
                # a given amount of memory to accommodate longer context lengths
                # or enable more requests to be processed simultaneously.
                shared_kv_cache_layers[layer_name] = kv_tgt_layer

        bind_kv_cache(self.compilation_config.static_forward_context,
                      self.gpu_cache, shared_kv_cache_layers)

    def _warm_up_model(self) -> None:
        # warm up sizes that are not in cudagraph capture sizes,
        # but users still want to compile for better performance,
        # e.g. for the max-num-batched token size in chunked prefill.
        warmup_sizes = self.vllm_config.compilation_config.compile_sizes.copy()
        if not self.model_config.enforce_eager:
            warmup_sizes = [
                x for x in warmup_sizes if x not in
                self.vllm_config.compilation_config.cudagraph_capture_sizes
            ]
        for size in sorted(warmup_sizes, reverse=True):
            logger.info("Compile and warming up model for size %d", size)
            self.model_runner._dummy_run(size)

        cuda_graph_memory_bytes = 0
        if not self.model_config.enforce_eager:
            cuda_graph_memory_bytes = self.model_runner.capture_model(
                self.gpu_cache)

        if (self.cache_config.kv_cache_memory_bytes is None
                and hasattr(self, "peak_activation_memory")):
            # Suggests optimal kv cache memory size if we rely on
            # memory_profiling to guess the kv cache memory size which
            # provides peak_activation_memory and a few other memory
            # consumption. `memory_profiling` does not consider
            # CUDAGraph memory size and may not utilize all gpu memory.
            # Users may want fine-grained control to specify kv cache
            # memory size.
            GiB = lambda b: round(b / GiB_bytes, 2)
            non_kv_cache_memory = (self.model_runner.model_memory_usage +
                                   self.peak_activation_memory +
                                   self.non_torch_memory +
                                   cuda_graph_memory_bytes)

            # empirically observed that the memory profiling may
            # slightly underestimate the memory consumption.
            # So leave a small buffer (=150MiB) to avoid OOM.
            redundancy_buffer_memory = 150 * (1 << 20)
            kv_cache_memory_bytes_to_gpu_limit = (
                self.baseline_snapshot.free_memory - non_kv_cache_memory -
                redundancy_buffer_memory)
            kv_cache_memory_bytes_to_requested_limit = (
                int(self.requested_memory) - non_kv_cache_memory -
                redundancy_buffer_memory)

            msg = (
                f"Free memory on device "
                f"({GiB(self.baseline_snapshot.free_memory)}/"
                f"{GiB(self.baseline_snapshot.total_memory)} GiB) on startup. "
                f"Desired GPU memory utilization is "
                f"({self.cache_config.gpu_memory_utilization}, "
                f"{GiB(self.requested_memory)} GiB). "
                f"Actual usage is {GiB(self.model_runner.model_memory_usage)} "
                f"GiB for weight, {GiB(self.peak_activation_memory)} GiB "
                f"for peak activation, {GiB(self.non_torch_memory)} GiB "
                f"for non-torch memory, and {GiB(cuda_graph_memory_bytes)} "
                f"GiB for CUDAGraph memory. Replace gpu_memory_utilization "
                f"config with `--kv-cache-memory="
                f"{kv_cache_memory_bytes_to_requested_limit}` to fit into "
                f"requested memory, or `--kv-cache-memory="
                f"{kv_cache_memory_bytes_to_gpu_limit}` to fully "
                f"utilize gpu memory. Current kv cache memory in use is "
                f"{int(self.available_kv_cache_memory)} bytes.")
            logger.info(msg)

        # 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)

    @property
    def do_metadata_broadcast(self) -> bool:
        return self.parallel_config.tensor_parallel_size > 1

    @property
    def kv_cache(self) -> Optional[List[List[torch.Tensor]]]:
        return self.gpu_cache
    
    @property
    def cache_engines(self) -> Optional[List[CacheEngine]]:
        return self.cache_engine

    @torch.inference_mode()
    def prepare_worker_input(
            self, execute_model_req: ExecuteModelRequest) -> WorkerInput:
        virtual_engine = execute_model_req.virtual_engine
        num_steps = execute_model_req.num_steps
        num_seq_groups = len(execute_model_req.seq_group_metadata_list)
        # `blocks_to_swap_in` and `blocks_to_swap_out` are cpu tensors.
        # they contain parameters to launch cudamemcpyasync.
        blocks_to_swap_in = torch.tensor(execute_model_req.blocks_to_swap_in,
                                         device="cpu",
                                         dtype=torch.int64).view(-1, 2)
        blocks_to_swap_out = torch.tensor(execute_model_req.blocks_to_swap_out,
                                          device="cpu",
                                          dtype=torch.int64).view(-1, 2)
        # `blocks_to_copy` is a gpu tensor. The src and tgt of
        # blocks to copy are in the same device, and `blocks_to_copy`
        # can be used directly within cuda kernels.
        blocks_to_copy = torch.tensor(execute_model_req.blocks_to_copy,
                                      device=self.device,
                                      dtype=torch.int64).view(-1, 2)

        return WorkerInput(
            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,
            virtual_engine=virtual_engine,
            num_steps=num_steps,
            kvcache_slot_to_be_moved=execute_model_req.kvcache_slot_to_be_moved
        )

    @torch.inference_mode()
    def execute_worker(self, worker_input: WorkerInput) -> None:
        virtual_engine = worker_input.virtual_engine
        # Issue cache operations.
        if (worker_input.blocks_to_swap_in is not None
                and worker_input.blocks_to_swap_in.numel() > 0):
            self.cache_engine[virtual_engine].swap_in(
                worker_input.blocks_to_swap_in)
        if (worker_input.blocks_to_swap_out is not None
                and worker_input.blocks_to_swap_out.numel() > 0):
            self.cache_engine[virtual_engine].swap_out(
                worker_input.blocks_to_swap_out)
        if (worker_input.blocks_to_copy is not None
                and worker_input.blocks_to_copy.numel() > 0):
            self.cache_engine[virtual_engine].copy(worker_input.blocks_to_copy)

        # tree-style generation need to move kvcache to correct position
        if worker_input.kvcache_slot_to_be_moved is not None:
            self.cache_engine[virtual_engine].move_caches(self.kv_cache[virtual_engine], 
                                                          worker_input.kvcache_slot_to_be_moved)

    def _get_cached_seq_group_metadata(
            self,
            seq_group_metadata_list: List[Union[SequenceGroupMetadata,
                                                SequenceGroupMetadataDelta]],
            finished_request_ids: List[str]) -> List[SequenceGroupMetadata]:
        """Return a list of cached Sequence Group Metadata after updating its
        state.

        It is used because scheduler only sends delta to workers to reduce
        the data payload size. The function also cleans up cache based on
        a given `finished_request_ids`.
        """
        new_seq_group_metadata_list = []
        for metadata_or_delta in seq_group_metadata_list:
            request_id = metadata_or_delta.request_id
            if request_id not in self._seq_group_metadata_cache:
                # The first prefill.
                assert isinstance(metadata_or_delta, SequenceGroupMetadata)
                self._seq_group_metadata_cache[request_id] = metadata_or_delta
            else:
                # The first prefill is already cached.
                if isinstance(metadata_or_delta, SequenceGroupMetadataDelta):
                    self._seq_group_metadata_cache[request_id].apply_delta(
                        metadata_or_delta)
                else:
                    # If metadata snapshot is sent again, it is
                    # preempted. Reset the cache because we need to start
                    # from scratch.
                    assert isinstance(metadata_or_delta, SequenceGroupMetadata)
                    self._seq_group_metadata_cache[
                        request_id] = metadata_or_delta

            new_seq_group_metadata_list.append(
                self._seq_group_metadata_cache[request_id])

        # Clean up finished ids
        for finished_id in finished_request_ids:
            del self._seq_group_metadata_cache[finished_id]

        return new_seq_group_metadata_list

    def _execute_model_spmd(
        self,
        execute_model_req: ExecuteModelRequest,
        intermediate_tensors: Optional[IntermediateTensors] = None,
    ) -> Optional[List[SamplerOutput]]:
        if execute_model_req is not None:
            new_seq_group_metadata_list = self._get_cached_seq_group_metadata(
                execute_model_req.seq_group_metadata_list,
                execute_model_req.finished_requests_ids)

            execute_model_req.seq_group_metadata_list = (
                new_seq_group_metadata_list)
        output = super()._execute_model_spmd(execute_model_req,
                                             intermediate_tensors)
        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 pin_lora(self, lora_id: int) -> bool:
        return self.model_runner.pin_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(
    vllm_config: VllmConfig,
    rank: int,
    distributed_init_method: Optional[str] = None,
    local_rank: int = -1,
) -> None:
    """Initialize the distributed environment."""
    parallel_config = vllm_config.parallel_config
    set_custom_all_reduce(not parallel_config.disable_custom_all_reduce)

    init_distributed_environment(parallel_config.world_size, rank,
                                 distributed_init_method, local_rank,
                                 current_platform.dist_backend)
    ensure_model_parallel_initialized(
        parallel_config.tensor_parallel_size,
        parallel_config.pipeline_parallel_size,
        parallel_config.decode_context_parallel_size)

    ensure_kv_transfer_initialized(vllm_config)


def _check_if_gpu_supports_dtype(torch_dtype: torch.dtype):
    # Check if the GPU supports the dtype.
    if torch_dtype == torch.bfloat16:  # noqa: SIM102
        if not current_platform.has_device_capability(80):
            capability = current_platform.get_device_capability()
            gpu_name = current_platform.get_device_name()

            if capability is None:
                compute_str = "does not have a compute capability"
            else:
                version_str = capability.as_version_str()
                compute_str = f"has compute capability {version_str}"

            raise ValueError(
                "Bfloat16 is only supported on GPUs with compute capability "
                f"of at least 8.0. Your {gpu_name} GPU {compute_str}. "
                "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, is_attention_free,
                                max_model_len, pipeline_parallel_size) -> None:
    if is_attention_free and num_gpu_blocks != 0:
        raise ValueError("No memory should be allocated for the cache blocks "
                         f"for an attention-free model, but {num_gpu_blocks} "
                         "blocks are allocated.")
    if not is_attention_free and 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 // pipeline_parallel_size)
    if not is_attention_free and 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.")