gpu_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 collections.abc import Callable
from contextlib import AbstractContextManager, nullcontext
from types import NoneType
from typing import TYPE_CHECKING, Any, cast

import numpy as np
import torch
import torch.distributed
import torch.nn as nn

import vllm.envs as envs
from vllm.config import CUDAGraphMode, VllmConfig, set_current_vllm_config
from vllm.config.compilation import CompilationMode
from vllm.distributed import (
    ensure_model_parallel_initialized,
    init_distributed_environment,
    set_custom_all_reduce,
)
from vllm.distributed.ec_transfer import ensure_ec_transfer_initialized
from vllm.distributed.eplb.eplb_utils import override_envs_for_eplb
from vllm.distributed.kv_transfer import (
    ensure_kv_transfer_initialized,
    ensure_kv_transfer_shutdown,
    get_kv_transfer_group,
    has_kv_transfer_group,
)
from vllm.distributed.parallel_state import (
    Handle,
    get_pcp_group,
    get_pp_group,
    get_tp_group,
)
from vllm.distributed.weight_transfer import WeightTransferEngineFactory
from vllm.logger import init_logger
from vllm.lora.request import LoRARequest
from vllm.model_executor.models.interfaces import is_mixture_of_experts
from vllm.model_executor.warmup.kernel_warmup import kernel_warmup
from vllm.platforms import current_platform
from vllm.profiler.wrapper import CudaProfilerWrapper, TorchProfilerWrapper
from vllm.sequence import IntermediateTensors
from vllm.tasks import SupportedTask
from vllm.tracing import instrument
from vllm.utils.mem_utils import MemorySnapshot, format_gib, memory_profiling
from vllm.utils.torch_utils import set_random_seed
from vllm.v1.core.sched.output import GrammarOutput, SchedulerOutput
from vllm.v1.engine import ReconfigureDistributedRequest, ReconfigureRankType
from vllm.v1.kv_cache_interface import KVCacheConfig, KVCacheSpec
from vllm.v1.outputs import (
    AsyncModelRunnerOutput,
    DraftTokenIds,
    ModelRunnerOutput,
)
from vllm.v1.utils import compute_iteration_details, report_usage_stats
from vllm.v1.worker.utils import is_residual_scattered_for_sp
from vllm.v1.worker.worker_base import WorkerBase
from vllm.v1.worker.workspace import init_workspace_manager

from .utils import request_memory

logger = init_logger(__name__)

if TYPE_CHECKING:
    from vllm.model_executor.model_loader.tensorizer import TensorizerConfig
    from vllm.v1.worker.gpu_model_runner import GPUModelRunner


class AsyncIntermediateTensors(IntermediateTensors):
    """IntermediateTensors with lazy comm synchronization"""

    def __init__(
        self,
        tensors: dict[str, torch.Tensor],
        comm_handles: list[Handle] | None = None,
        comm_postprocess: list[Callable[[], None]] | None = None,
    ) -> None:
        super().__init__(tensors)
        self._comm_handles = comm_handles
        self._comm_postprocess = comm_postprocess
        self._comm_waited = False

    def wait_for_comm(self) -> None:
        if self._comm_waited:
            return
        if self._comm_handles:
            for handle in self._comm_handles:
                handle.wait()
        if self._comm_postprocess:
            for fn in self._comm_postprocess:
                fn()
        self._comm_waited = True

    def __getattribute__(self, name: str):
        # ensure `.tensors` is ready before use
        if name == "tensors" and not object.__getattribute__(self, "_comm_waited"):
            object.__getattribute__(self, "wait_for_comm")()
        return object.__getattribute__(self, name)


class Worker(WorkerBase):
    def __init__(
        self,
        vllm_config: VllmConfig,
        local_rank: int,
        rank: int,
        distributed_init_method: str,
        is_driver_worker: bool = False,
    ):
        super().__init__(
            vllm_config=vllm_config,
            local_rank=local_rank,
            rank=rank,
            distributed_init_method=distributed_init_method,
            is_driver_worker=is_driver_worker,
        )

        # configure float32 matmul precision according to vLLM env.
        precision = envs.VLLM_FLOAT32_MATMUL_PRECISION
        torch.set_float32_matmul_precision(precision)

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

        # Weight transfer engine (initialized on-demand)
        self.weight_transfer_engine = (
            WeightTransferEngineFactory.create_engine(
                self.vllm_config.weight_transfer_config,
                self.vllm_config.parallel_config,
            )
            if self.vllm_config.weight_transfer_config is not None
            else None
        )

        # Torch/CUDA profiler. Enabled and configured through profiler_config.
        # Profiler wrapper is created lazily in profile() when start is called,
        # so we have all the information needed for proper trace naming.
        self.profiler: Any | None = None
        self.profiler_config = vllm_config.profiler_config

        # Only validate profiler config is valid, don't instantiate yet
        if self.profiler_config.profiler not in ("torch", "cuda", None):
            raise ValueError(f"Unknown profiler type: {self.profiler_config.profiler}")

        self.use_v2_model_runner = envs.VLLM_USE_V2_MODEL_RUNNER
        # pending non-blocking PP send work from the previous iteration
        self._pp_send_work: list[Handle] = []

    def sleep(self, level: int = 1) -> None:
        from vllm.device_allocator.cumem import CuMemAllocator

        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 %s GiB memory, %s GiB memory is still in use.",
            format_gib(freed_bytes),
            format_gib(used_bytes),
        )

    def wake_up(self, tags: list[str] | None = None) -> None:
        from vllm.device_allocator.cumem import CuMemAllocator

        allocator = CuMemAllocator.get_instance()
        allocator.wake_up(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 = {}

        # If the KV cache has just been woken up,
        # the internal state of cache_engine must be reset,
        # especially the FP8 scaling factor.
        if (
            (tags is None or "kv_cache" in tags)
            and self.cache_config.cache_dtype.startswith("fp8")
            and hasattr(self.model_runner, "init_fp8_kv_scales")
        ):
            self.model_runner.init_fp8_kv_scales()

    def _maybe_get_memory_pool_context(self, tag: str) -> AbstractContextManager:
        if self.vllm_config.model_config.enable_sleep_mode:
            from vllm.device_allocator.cumem import CuMemAllocator

            allocator = CuMemAllocator.get_instance()
            if tag == "weights":
                assert allocator.get_current_usage() == 0, (
                    "Sleep mode can only be used for one instance per process."
                )
            return allocator.use_memory_pool(tag=tag)
        else:
            return nullcontext()

    def initialize_cache(self, num_gpu_blocks: int, num_cpu_blocks: int) -> None:
        self.cache_config.num_gpu_blocks = num_gpu_blocks
        self.cache_config.num_cpu_blocks = num_cpu_blocks

    @instrument(span_name="Init device")
    def init_device(self):
        if self.device_config.device_type == "cuda":
            # This env var set by Ray causes exceptions with graph building.
            os.environ.pop("NCCL_ASYNC_ERROR_HANDLING", None)
            parallel_config = self.parallel_config
            if (
                parallel_config.distributed_executor_backend
                not in ("ray", "external_launcher")
                and parallel_config.data_parallel_backend != "ray"
                and parallel_config.nnodes_within_dp == 1
            ):
                # Use local DP rank if available, otherwise use global DP rank.
                dp_local_rank = self.parallel_config.data_parallel_rank_local
                if dp_local_rank is None:
                    dp_local_rank = self.parallel_config.data_parallel_index

                tp_pp_world_size = (
                    self.parallel_config.pipeline_parallel_size
                    * self.parallel_config.tensor_parallel_size
                )

                # DP_LOCAL_RANK * TP_PP_WORLD_SIZE + TP_LOCAL_RANK
                self.local_rank += dp_local_rank * tp_pp_world_size
                assert self.local_rank < torch.cuda.device_count(), (
                    f"DP adjusted local rank {self.local_rank} is out of bounds. "
                )
                visible_device_count = (
                    torch.cuda.device_count() if torch.cuda.is_available() else 0
                )
                assert self.parallel_config.local_world_size <= visible_device_count, (
                    f"local_world_size ({self.parallel_config.local_world_size}) must "
                    f"be less than or equal to the number of visible devices "
                    f"({visible_device_count})."
                )

            self.device = torch.device(f"cuda:{self.local_rank}")
            current_platform.set_device(self.device)

            current_platform.check_if_supports_dtype(self.model_config.dtype)

            # Initialize the distributed environment BEFORE taking
            # memory snapshot
            # This ensures NCCL buffers are allocated before we measure
            # available memory
            init_worker_distributed_environment(
                self.vllm_config,
                self.rank,
                self.distributed_init_method,
                self.local_rank,
                current_platform.dist_backend,
            )

            if self.use_v2_model_runner:
                logger.info_once("Using V2 Model Runner", scope="local")

            # Set random seed.
            set_random_seed(self.model_config.seed)

            # Now take memory snapshot after NCCL is initialized
            gc.collect()
            torch.cuda.empty_cache()

            # take current memory snapshot
            self.init_snapshot = init_snapshot = MemorySnapshot(device=self.device)
            self.requested_memory = request_memory(init_snapshot, self.cache_config)
            logger.debug("worker init memory snapshot: %r", self.init_snapshot)
            logger.debug(
                "worker requested memory: %sGiB", format_gib(self.requested_memory)
            )
        else:
            raise RuntimeError(f"Not support device type: {self.device_config.device}")

        # Initialize workspace manager
        num_ubatches = 2 if self.vllm_config.parallel_config.enable_dbo else 1
        init_workspace_manager(self.device, num_ubatches)

        # Construct the model runner
        if self.use_v2_model_runner:
            from vllm.v1.worker.gpu.model_runner import (
                GPUModelRunner as GPUModelRunnerV2,
            )

            # HACK(woosuk): This is a temporary fix to avoid type errors.
            self.model_runner: GPUModelRunner = GPUModelRunnerV2(  # type: ignore
                self.vllm_config, self.device
            )
        else:
            from vllm.v1.worker.gpu_model_runner import (
                GPUModelRunner as GPUModelRunnerV1,
            )

            self.model_runner = GPUModelRunnerV1(self.vllm_config, self.device)

        if self.rank == 0:
            # If usage stat is enabled, collect relevant info.
            report_usage_stats(self.vllm_config)

    # FIXME(youkaichao & ywang96): Use TorchDispatchMode instead of memory pool
    # to hijack tensor allocation.
    def load_model(self) -> None:
        eep_scale_up = os.environ.get("VLLM_ELASTIC_EP_SCALE_UP_LAUNCH") == "1"
        with (
            self._maybe_get_memory_pool_context(tag="weights"),
            set_current_vllm_config(self.vllm_config),
        ):
            self.model_runner.load_model(eep_scale_up=eep_scale_up)

    def update_config(self, overrides: dict[str, Any]) -> None:
        self.model_runner.update_config(overrides)

    def reload_weights(self, *args, **kwargs) -> None:
        self.model_runner.reload_weights(*args, **kwargs)

    @torch.inference_mode()
    def determine_available_memory(self) -> int:
        """Profiles the peak memory usage of the model to determine how much
        memory can be used for KV cache without OOMs.

        The engine will first conduct a profiling of the existing memory usage.
        Then, it calculates the free memory that can be used for KV cache in
        bytes.

        Tip:
            You may limit the usage of GPU memory
            by adjusting the `gpu_memory_utilization` parameter.
        """
        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()

            msg = (
                f"Initial free memory {format_gib(self.init_snapshot.free_memory)} "
                f"GiB, reserved {format_gib(kv_cache_memory_bytes)} GiB memory for "
                "KV Cache as specified by kv_cache_memory_bytes config and "
                "skipped memory profiling. This 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 kv_cache_memory_bytes

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

        self.non_torch_memory = profile_result.non_torch_increase
        self.peak_activation_memory = profile_result.torch_peak_increase

        free_gpu_memory = profile_result.after_profile.free_memory
        # NOTE(woosuk): Here we assume that the other processes using the same
        # GPU did not change their memory usage during the profiling.
        assert self.init_snapshot.free_memory >= free_gpu_memory, (
            "Error in memory profiling. "
            f"Initial free memory {format_gib(self.init_snapshot.free_memory)} GiB, "
            f"current free memory {format_gib(free_gpu_memory)} GiB. "
            "This happens when other processes sharing the same container "
            "release GPU memory while vLLM is profiling during initialization. "
            "To fix this, ensure consistent GPU memory allocation or "
            "isolate vLLM in its own container."
        )
        self.available_kv_cache_memory_bytes = (
            self.requested_memory - profile_result.non_kv_cache_memory
        )

        unrequested_memory = self.init_snapshot.free_memory - self.requested_memory
        logger.debug(
            "Initial free memory: %s GiB; Requested memory: %f (util), %s GiB",
            format_gib(self.init_snapshot.free_memory),
            self.cache_config.gpu_memory_utilization,
            format_gib(self.requested_memory),
        )
        logger.debug(
            "Free memory after profiling: %s GiB (total), %s GiB (within requested)",
            format_gib(free_gpu_memory),
            format_gib(free_gpu_memory - unrequested_memory),
        )
        logger.debug(profile_result)
        logger.info_once(
            "Available KV cache memory: %s GiB",
            format_gib(self.available_kv_cache_memory_bytes),
            scope="local",
        )

        return int(self.available_kv_cache_memory_bytes)

    def get_kv_connector_handshake_metadata(self) -> dict | None:
        """Get KV connector metadata from this worker if available."""

        if not has_kv_transfer_group():
            return None

        connector = get_kv_transfer_group()
        # Return None for connectors that don't need to exchange handshake
        # metadata across workers.
        if (metadata := connector.get_handshake_metadata()) is None:
            return None

        tp_rank = get_tp_group().rank_in_group
        return {tp_rank: metadata}

    def get_kv_cache_spec(self) -> dict[str, KVCacheSpec]:
        return self.model_runner.get_kv_cache_spec()

    def update_max_model_len(self, max_model_len: int) -> None:
        """Update max_model_len after auto-fit to GPU memory.

        This is called when max_model_len=-1 is used and the engine
        automatically determines the maximum context length that fits
        in GPU memory. Workers need to update their cached max_model_len
        to match the engine's decision.
        """
        self.model_config.max_model_len = max_model_len
        if self.model_runner is not None:
            self.model_runner.update_max_model_len(max_model_len)
        logger.debug("Updated max_model_len to %d", max_model_len)

    @instrument(span_name="Allocate KV cache")
    def initialize_from_config(self, kv_cache_config: KVCacheConfig) -> None:
        """Allocate GPU KV cache with the specified kv_cache_config."""

        # Init kv cache connector here, because it requires
        # `kv_cache_config`.
        # NOTE(Kuntai): This need to be done before `initialize_kv_cache`,
        # because `initialize_kv_cache` will inject kv cache groups not
        # related to kv cache connector (e.g. kv cache sharing layers).
        ensure_kv_transfer_initialized(self.vllm_config, kv_cache_config)

        if self.vllm_config.model_config.enable_sleep_mode:
            from vllm.device_allocator.cumem import CuMemAllocator

            allocator = CuMemAllocator.get_instance()
            with allocator.use_memory_pool(tag="kv_cache"):
                self.model_runner.initialize_kv_cache(kv_cache_config)
        else:
            self.model_runner.initialize_kv_cache(kv_cache_config)

    @instrument(span_name="Warmup (GPU)")
    def compile_or_warm_up_model(self) -> None:
        warmup_sizes = []

        if self.vllm_config.compilation_config.mode == CompilationMode.VLLM_COMPILE:
            # 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.
            compile_sizes = self.vllm_config.compilation_config.compile_sizes
            warmup_sizes = compile_sizes.copy() if compile_sizes is not None else []
            cg_capture_sizes: list[int] = []

            if self.vllm_config.compilation_config.cudagraph_mode != CUDAGraphMode.NONE:
                cg_sizes = self.vllm_config.compilation_config.cudagraph_capture_sizes
                cg_capture_sizes = [] if cg_sizes is None else cg_sizes
                warmup_sizes = [x for x in warmup_sizes if x not in cg_capture_sizes]

            compile_ranges = self.vllm_config.compilation_config.get_compile_ranges()
            # For each compile_range, if none of the batch sizes
            # in warmup_sizes or cudagraph_capture_sizes are in the range,
            # add the end of the range to ensure compilation/warmup.
            all_sizes = set(cg_capture_sizes)
            all_sizes.update([x for x in warmup_sizes if isinstance(x, int)])
            for compile_range in compile_ranges:
                if not any(x in compile_range for x in all_sizes):
                    warmup_sizes.append(compile_range.end)

        # We skip EPLB here since we don't want to record dummy metrics
        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, skip_eplb=True, remove_lora=False)
        self.model_runner.maybe_remove_all_loras(self.model_runner.lora_config)

        # Warmup and tune the kernels used during model execution before
        # cuda graph capture.
        kernel_warmup(self)

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

        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.

            # 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)
            non_kv_cache_memory = (
                self.model_runner.model_memory_usage
                + self.peak_activation_memory
                + self.non_torch_memory
                + cuda_graph_memory_bytes
            )
            kv_cache_memory_bytes_to_gpu_limit = (
                self.init_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"({format_gib(self.init_snapshot.free_memory)}/"
                f"{format_gib(self.init_snapshot.total_memory)} GiB) on startup. "
                f"Desired GPU memory utilization is "
                f"({self.cache_config.gpu_memory_utilization}, "
                f"{format_gib(self.requested_memory)} GiB). "
                f"Actual usage is {format_gib(self.model_runner.model_memory_usage)} "
                f"GiB for weight, {format_gib(self.peak_activation_memory)} GiB "
                f"for peak activation, {format_gib(self.non_torch_memory)} GiB "
                f"for non-torch memory, and {format_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}` "
                f"({format_gib(kv_cache_memory_bytes_to_requested_limit)} GiB) to fit "
                f"into requested memory, or `--kv-cache-memory="
                f"{kv_cache_memory_bytes_to_gpu_limit}` "
                f"({format_gib(kv_cache_memory_bytes_to_gpu_limit)} GiB) to fully "
                f"utilize gpu memory. Current kv cache memory in use is "
                f"{format_gib(self.available_kv_cache_memory_bytes)} GiB."
            )

            logger.debug(msg)

        # Warm up sampler and preallocate memory buffer for logits and other
        # sampling related tensors of max possible shape to avoid memory
        # fragmentation issue.
        # NOTE: This is called after `capture_model` on purpose to prevent
        # memory buffers from being cleared by `torch.cuda.empty_cache`.
        if get_pp_group().is_last_rank:
            max_num_reqs = min(
                self.scheduler_config.max_num_seqs,
                self.scheduler_config.max_num_batched_tokens,
            )

            # We skip EPLB here since we don't want to record dummy metrics
            hidden_states, last_hidden_states = self.model_runner._dummy_run(
                num_tokens=max_num_reqs,
                skip_eplb=True,
                cudagraph_runtime_mode=CUDAGraphMode.NONE,
            )
            if self.model_runner.is_pooling_model:
                self.model_runner._dummy_pooler_run(hidden_states)
            else:
                self.model_runner._dummy_sampler_run(hidden_states=last_hidden_states)

        # 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 reset_mm_cache(self) -> None:
        self.model_runner.reset_mm_cache()

    def reset_encoder_cache(self) -> None:
        self.model_runner.reset_encoder_cache()

    def get_model(self) -> nn.Module:
        return self.model_runner.get_model()

    def get_supported_tasks(self) -> tuple[SupportedTask, ...]:
        return self.model_runner.get_supported_tasks()

    def get_encoder_timing_stats(self) -> dict[str, dict[str, float | int]]:
        """Get encoder timing stats from model runner."""
        return self.model_runner.get_encoder_timing_stats()

    def annotate_profile(self, scheduler_output):
        # add trace annotation so that we can easily distinguish
        # context/generation request numbers in each iteration.
        # A context request is a request that has not yet generated any tokens
        if not self.profiler:
            return nullcontext()

        self.profiler.step()

        iteration_details = compute_iteration_details(scheduler_output)

        annotation = "".join(
            [
                "execute_context_",
                str(iteration_details.num_ctx_requests),
                "(",
                str(iteration_details.num_ctx_tokens),
                ")_generation_",
                str(iteration_details.num_generation_requests),
                "(",
                str(iteration_details.num_generation_tokens),
                ")",
            ]
        )
        return self.profiler.annotate_context_manager(annotation)

    @torch.inference_mode()
    def sample_tokens(
        self, grammar_output: "GrammarOutput | None"
    ) -> ModelRunnerOutput | AsyncModelRunnerOutput:
        return self.model_runner.sample_tokens(grammar_output)

    @torch.inference_mode()
    def execute_model(
        self, scheduler_output: "SchedulerOutput"
    ) -> ModelRunnerOutput | AsyncModelRunnerOutput | None:
        # ensure any previous non-blocking PP sends are complete
        if self._pp_send_work:
            for handle in self._pp_send_work:
                handle.wait()
            self._pp_send_work = []

        intermediate_tensors = None
        forward_pass = scheduler_output.total_num_scheduled_tokens > 0
        num_scheduled_tokens = scheduler_output.total_num_scheduled_tokens
        all_gather_tensors = {}
        compilation_config = self.vllm_config.compilation_config
        parallel_config = self.vllm_config.parallel_config

        if (
            parallel_config.pipeline_parallel_size > 1
            and compilation_config.pass_config.enable_sp
            and forward_pass
        ):
            # currently only supported by V1 GPUModelRunner
            assert not self.use_v2_model_runner
            num_scheduled_tokens_np = np.array(
                list(scheduler_output.num_scheduled_tokens.values()),
                dtype=np.int32,
            )
            # TODO(lucas): This is pretty gross; ideally we should only ever call
            # `_determine_batch_execution_and_padding` once (will get called again
            # in `execute_model`) but this requires a larger refactor of PP.
            _, batch_desc, _, _, _ = (
                self.model_runner._determine_batch_execution_and_padding(
                    num_tokens=num_scheduled_tokens,
                    num_reqs=len(num_scheduled_tokens_np),
                    num_scheduled_tokens_np=num_scheduled_tokens_np,
                    max_num_scheduled_tokens=num_scheduled_tokens_np.max(),
                    use_cascade_attn=False,  # TODO(lucas): Handle cascade attention
                )
            )
            all_gather_tensors = {
                "residual": not is_residual_scattered_for_sp(
                    self.vllm_config, batch_desc.num_tokens
                )
            }

        if forward_pass and not get_pp_group().is_first_rank:
            tensor_dict, comm_handles, comm_postprocess = (
                get_pp_group().irecv_tensor_dict(
                    all_gather_group=get_tp_group(),
                    all_gather_tensors=all_gather_tensors,
                )
            )
            assert tensor_dict is not None
            intermediate_tensors = AsyncIntermediateTensors(
                tensor_dict,
                comm_handles=comm_handles,
                comm_postprocess=comm_postprocess,
            )

        with self.annotate_profile(scheduler_output):
            output = self.model_runner.execute_model(
                scheduler_output, intermediate_tensors
            )
            if isinstance(
                output, ModelRunnerOutput | AsyncModelRunnerOutput | NoneType
            ):
                return output

        assert isinstance(output, IntermediateTensors)
        parallel_config = self.vllm_config.parallel_config
        assert (
            parallel_config.distributed_executor_backend != "external_launcher"
            and not get_pp_group().is_last_rank
        )

        # launch non-blocking send of intermediate tensors
        self._pp_send_work = get_pp_group().isend_tensor_dict(
            output.tensors,
            all_gather_group=get_tp_group(),
            all_gather_tensors=all_gather_tensors,
        )

        return None

    def take_draft_token_ids(self) -> DraftTokenIds | None:
        return self.model_runner.take_draft_token_ids()

    def profile(self, is_start: bool = True, profile_prefix: str | None = None):
        # Check if profiling is enabled
        if self.profiler_config is None or self.profiler_config.profiler is None:
            raise RuntimeError(
                "Profiling is not enabled. Please set --profiler-config to enable "
                "profiling. Example: "
                "'--profiler-config.profiler=torch --profiler-config.torch_profiler_dir"
                "=YOUR_DIR_PATH_TO_DUMP_TRACE'"
            )

        if is_start:
            # Generate the trace name by combining prefix with comprehensive rank suffix
            from vllm.distributed.utils import get_worker_rank_suffix

            rank_suffix = get_worker_rank_suffix(global_rank=self.rank)

            # Build the full trace name
            if profile_prefix:
                trace_name = f"{profile_prefix}_{rank_suffix}"
            else:
                trace_name = rank_suffix

            # Create the profiler wrapper only on the first start call
            if self.profiler is None:
                if self.profiler_config.profiler == "torch":
                    self.profiler = TorchProfilerWrapper(
                        self.profiler_config,
                        worker_name=trace_name,
                        local_rank=self.local_rank,
                        activities=["CPU", "CUDA"],
                    )
                    logger.debug(
                        "Starting torch profiler with trace name: %s", trace_name
                    )
                elif self.profiler_config.profiler == "cuda":
                    self.profiler = CudaProfilerWrapper(self.profiler_config)
                    logger.debug("Starting CUDA profiler")
                self.profiler.start()
            else:
                # Profiler already initialized. Restart profiling but keep
                # the original trace name from the first initialization.
                self.profiler.start()
        else:
            if self.profiler is None:
                logger.warning("Profiler was not started, nothing to stop.")
                return
            self.profiler.stop()

    def execute_dummy_batch(self) -> None:
        self.model_runner._dummy_run(1, uniform_decode=True)

    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()

    def pin_lora(self, lora_id: int) -> bool:
        return self.model_runner.pin_lora(lora_id)

    def check_health(self) -> None:
        # worker will always be healthy as long as it's running.
        return

    def _eplb_before_scale_down(self, old_ep_size: int, new_ep_size: int) -> None:
        from vllm.distributed.parallel_state import get_ep_group

        if get_ep_group().rank == 0:
            logger.info(
                "[Elastic EP] Starting expert resharding before scaling down..."
            )
        rank_mapping = {
            old_ep_rank: old_ep_rank if old_ep_rank < new_ep_size else -1
            for old_ep_rank in range(old_ep_size)
        }
        assert self.model_runner.eplb_state is not None
        self.model_runner.eplb_state.rearrange(
            execute_shuffle=True,
            global_expert_loads=None,
            rank_mapping=rank_mapping,
        )
        torch.cuda.synchronize()
        if get_ep_group().rank == 0:
            logger.info("[Elastic EP] Expert resharding completed!")

    def _eplb_after_scale_up(
        self,
        old_ep_size: int,
        new_ep_size: int,
        global_expert_loads: list[torch.Tensor] | None,
    ) -> None:
        from vllm.distributed.parallel_state import get_ep_group

        if get_ep_group().rank == 0:
            logger.info("[Elastic EP] Starting expert resharding after scaling up...")
        rank_mapping = {old_ep_rank: old_ep_rank for old_ep_rank in range(old_ep_size)}
        assert self.model_runner.eplb_state is not None
        self.model_runner.eplb_state.rearrange(
            execute_shuffle=True,
            global_expert_loads=global_expert_loads,
            rank_mapping=rank_mapping,
        )
        if get_ep_group().rank == 0:
            logger.info("[Elastic EP] Expert resharding completed!")

    def _reconfigure_parallel_config(
        self, reconfig_request: ReconfigureDistributedRequest
    ) -> None:
        """
        Update parallel config with provided reconfig_request
        """
        parallel_config = self.vllm_config.parallel_config
        parallel_config.data_parallel_size = reconfig_request.new_data_parallel_size
        if (
            reconfig_request.new_data_parallel_rank
            != ReconfigureRankType.KEEP_CURRENT_RANK
        ):
            parallel_config.data_parallel_rank = reconfig_request.new_data_parallel_rank
        if (
            reconfig_request.new_data_parallel_rank_local
            != ReconfigureRankType.KEEP_CURRENT_RANK
        ):
            parallel_config.data_parallel_rank_local = (
                reconfig_request.new_data_parallel_rank_local
            )
        parallel_config.data_parallel_master_ip = (
            reconfig_request.new_data_parallel_master_ip
        )
        parallel_config.data_parallel_master_port = (
            reconfig_request.new_data_parallel_master_port
        )

    def _reconfigure_moe(
        self, old_ep_size: int, new_ep_size: int
    ) -> list[torch.Tensor] | None:
        """
        Reconfigure MoE modules with provided reconfig_request

        Return the global expert load if new_ep_size > old_ep_size,
        otherwise None
        """
        from vllm.distributed.parallel_state import (
            get_dp_group,
            get_ep_group,
            prepare_communication_buffer_for_model,
        )
        from vllm.model_executor.layers.fused_moe.layer import (
            FusedMoE,
            FusedMoEParallelConfig,
        )

        parallel_config = self.vllm_config.parallel_config

        def get_moe_modules(model: torch.nn.Module) -> list[FusedMoE]:
            return [
                module
                for module in model.modules()
                if (
                    module.__class__.__name__ == "FusedMoE"
                    or module.__class__.__name__ == "SharedFusedMoE"
                )
            ]

        def update_moe_modules(moe_modules: list[FusedMoE], num_local_experts: int):
            assert all(
                module.moe_config.num_local_experts == num_local_experts
                for module in moe_modules
            ), "All MoE modules must have the same number of experts"
            for module in moe_modules:
                module.moe_config.num_experts = num_local_experts * new_ep_size
                module.global_num_experts = module.moe_config.num_experts
                tp_size = get_tp_group().world_size
                is_sequence_parallel = parallel_config.use_sequence_parallel_moe
                sp_size = tp_size if is_sequence_parallel else 1
                module.moe_parallel_config = FusedMoEParallelConfig.make(
                    tp_size_=tp_size,
                    pcp_size_=get_pcp_group().world_size,
                    dp_size_=get_dp_group().world_size,
                    sp_size_=sp_size,
                    vllm_parallel_config=parallel_config,
                )
                module.moe_config.moe_parallel_config = module.moe_parallel_config
            return moe_modules

        model_moe_modules = get_moe_modules(self.model_runner.model)
        num_local_experts = model_moe_modules[0].moe_config.num_local_experts

        update_moe_modules(model_moe_modules, num_local_experts)
        drafter_model = None
        if hasattr(self.model_runner, "drafter") and hasattr(
            self.model_runner.drafter, "model"
        ):
            drafter_model = self.model_runner.drafter.model
        if drafter_model is not None and is_mixture_of_experts(drafter_model):
            drafter_moe_modules = get_moe_modules(drafter_model)
            # Check if drafter and model have matching configs
            assert (
                drafter_moe_modules[0].moe_config.num_local_experts == num_local_experts
            ), "Drafter and model configs should be the same"
            update_moe_modules(drafter_moe_modules, num_local_experts)

        if new_ep_size < old_ep_size:
            num_local_physical_experts = num_local_experts
            assert self.model_runner.eplb_state is not None
            new_physical_experts = (
                self.model_runner.eplb_state.physical_to_logical_map.shape[1]  # type: ignore[attr-defined]
            )
            parallel_config.eplb_config.num_redundant_experts = (
                new_physical_experts
                - self.model_runner.eplb_state.logical_replica_count.shape[1]  # type: ignore[attr-defined]
            )
            global_expert_loads = None
        else:
            num_local_physical_experts_tensor = torch.tensor(
                [num_local_experts], dtype=torch.int32, device="cpu"
            )
            torch.distributed.broadcast(
                num_local_physical_experts_tensor,
                group=get_ep_group().cpu_group,
                group_src=0,
            )
            num_local_physical_experts = int(num_local_physical_experts_tensor.item())
            new_physical_experts = num_local_physical_experts * new_ep_size
            assert self.model_runner.eplb_state is not None
            global_expert_loads_any = self.model_runner.eplb_state.rearrange(
                execute_shuffle=False
            )
            global_expert_loads = cast(list[torch.Tensor], global_expert_loads_any)
            parallel_config.eplb_config.num_redundant_experts = (
                new_physical_experts - global_expert_loads[0].shape[1]
            )
        prepare_communication_buffer_for_model(self.model_runner.model)
        if drafter_model is not None:
            prepare_communication_buffer_for_model(drafter_model)
        self.model_runner.model.update_physical_experts_metadata(
            num_physical_experts=new_physical_experts,
            num_local_physical_experts=num_local_physical_experts,
        )
        return global_expert_loads

    def reinitialize_distributed(
        self, reconfig_request: ReconfigureDistributedRequest
    ) -> None:
        from vllm.config import set_current_vllm_config
        from vllm.distributed.parallel_state import (
            cleanup_dist_env_and_memory,
            get_ep_group,
        )

        old_ep_size = get_ep_group().world_size
        old_ep_rank = get_ep_group().rank
        new_ep_size = (
            reconfig_request.new_data_parallel_size
            * get_tp_group().world_size
            * get_pp_group().world_size
        )
        if new_ep_size < old_ep_size:
            self._eplb_before_scale_down(old_ep_size, new_ep_size)

        cleanup_dist_env_and_memory()

        if (
            reconfig_request.new_data_parallel_rank
            == ReconfigureRankType.SHUTDOWN_CURRENT_RANK
        ):
            assert old_ep_rank >= new_ep_size
            # shutdown
            return

        self._reconfigure_parallel_config(reconfig_request)

        with set_current_vllm_config(self.vllm_config):
            init_worker_distributed_environment(
                self.vllm_config,
                self.rank,
                self.distributed_init_method,
                self.local_rank,
            )

        global_expert_loads = self._reconfigure_moe(old_ep_size, new_ep_size)

        if new_ep_size > old_ep_size:
            assert global_expert_loads is not None
            self._eplb_after_scale_up(old_ep_size, new_ep_size, global_expert_loads)

    def save_sharded_state(
        self,
        path: str,
        pattern: str | None = None,
        max_size: int | None = None,
    ) -> None:
        from vllm.model_executor.model_loader import ShardedStateLoader

        ShardedStateLoader.save_model(
            self.model_runner.model,
            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,
        )

    def init_weight_transfer_engine(self, init_info: dict) -> None:
        """
        Initialize weight transfer mechanism.
        For NCCL backend, this creates a process group with the trainer.

        Args:
            init_info: Dictionary containing backend-specific initialization info
        """
        if self.weight_transfer_engine is None:
            raise RuntimeError(
                "Weight transfer not configured. "
                "Please set weight_transfer_config to enable weight transfer."
            )
        # Parse dict into backend-specific typed dataclass
        typed_init_info = self.weight_transfer_engine.parse_init_info(init_info)
        self.weight_transfer_engine.init_transfer_engine(typed_init_info)

    def update_weights(self, update_info: dict) -> None:
        """
        Batched weight update from the trainer.

        Args:
            update_info: Dictionary containing backend-specific update info
        """
        if self.weight_transfer_engine is None:
            raise RuntimeError(
                "Weight transfer not configured. "
                "Please set weight_transfer_config to enable weight transfer."
            )

        # Parse dict into backend-specific typed dataclass
        typed_update_info = self.weight_transfer_engine.parse_update_info(update_info)

        model = self.model_runner.model

        if typed_update_info.is_checkpoint_format:
            from vllm.model_executor.model_loader.reload import (
                finalize_layerwise_reload,
                initialize_layerwise_reload,
            )

            # Use layerwise reload pattern for checkpoint format weights
            with torch.device(self.device):
                initialize_layerwise_reload(model)
                self.weight_transfer_engine.receive_weights(
                    typed_update_info,
                    load_weights=model.load_weights,
                )
                finalize_layerwise_reload(model, self.model_config)
        else:
            # Weights are already in kernel format, copy directly
            def load_weights_direct(
                weights: list[tuple[str, torch.Tensor]],
            ) -> None:
                for name, weight in weights:
                    param = model.get_parameter(name)
                    param.copy_(weight)

            self.weight_transfer_engine.receive_weights(
                typed_update_info,
                load_weights=load_weights_direct,
            )

    def shutdown(self) -> None:
        # has_kv_transfer_group can be None during interpreter shutdown.
        if ensure_kv_transfer_shutdown is not None:
            ensure_kv_transfer_shutdown()
        if self.profiler is not None:
            self.profiler.shutdown()

        if weight_transfer_engine := getattr(self, "weight_transfer_engine", None):
            weight_transfer_engine.shutdown()


def init_worker_distributed_environment(
    vllm_config: VllmConfig,
    rank: int,
    distributed_init_method: str | None = None,
    local_rank: int = -1,
    backend: str = "nccl",
) -> None:
    """Initialize the distributed environment."""
    attention_config = vllm_config.attention_config
    parallel_config = vllm_config.parallel_config
    from vllm.model_executor.layers.batch_invariant import init_batch_invariance

    init_batch_invariance(attention_config.backend)
    override_envs_for_eplb(parallel_config)
    set_custom_all_reduce(not parallel_config.disable_custom_all_reduce)

    init_method = distributed_init_method or "env://"
    init_distributed_environment(
        parallel_config.world_size, rank, init_method, local_rank, backend
    )

    ensure_model_parallel_initialized(
        parallel_config.tensor_parallel_size,
        parallel_config.pipeline_parallel_size,
        parallel_config.prefill_context_parallel_size,
        parallel_config.decode_context_parallel_size,
    )

    # Init ec connector here before KV caches caches init
    # NOTE: We do not init KV caches for Encoder-only instance in EPD disagg mode
    ensure_ec_transfer_initialized(vllm_config)