cudagraph_utils.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from collections.abc import Callable
from typing import Any

import numpy as np
import torch
import torch.nn as nn
from tqdm import tqdm

from vllm.config import VllmConfig
from vllm.config.compilation import CUDAGraphMode
from vllm.distributed.parallel_state import graph_capture, is_global_first_rank
from vllm.forward_context import BatchDescriptor, set_forward_context
from vllm.utils.math_utils import cdiv
from vllm.v1.attention.backend import AttentionMetadataBuilder
from vllm.v1.kv_cache_interface import KVCacheConfig
from vllm.v1.worker.gpu.attn_utils import (
    build_attn_metadata,
    build_slot_mappings_by_layer,
)
from vllm.v1.worker.gpu.block_table import BlockTables
from vllm.v1.worker.gpu.dp_utils import make_num_tokens_across_dp
from vllm.v1.worker.gpu.input_batch import InputBuffers


class CudaGraphManager:
    def __init__(self, vllm_config: VllmConfig, uses_mrope: bool, device: torch.device):
        self.vllm_config = vllm_config
        self.scheduler_config = vllm_config.scheduler_config
        self.uses_mrope = uses_mrope
        self.device = device

        self.max_model_len = vllm_config.model_config.max_model_len
        self.max_num_reqs = self.scheduler_config.max_num_seqs
        self.max_num_tokens = self.scheduler_config.max_num_batched_tokens
        self.dp_size = vllm_config.parallel_config.data_parallel_size

        self.uniform_decode_query_len = 1
        spec_config = vllm_config.speculative_config
        if spec_config is not None:
            self.uniform_decode_query_len += spec_config.num_speculative_tokens

        self.compilation_config = vllm_config.compilation_config
        assert self.compilation_config is not None
        self.cudagraph_mode = self.compilation_config.cudagraph_mode

        use_uniform_decode_cudagraph = (
            self.cudagraph_mode.decode_mode() == CUDAGraphMode.FULL
            and self.cudagraph_mode.separate_routine()
        )
        self.cudagraph_sizes, self.uniform_decode_cudagraph_sizes = get_cudagraph_sizes(
            self.compilation_config.cudagraph_capture_sizes,
            self.max_num_reqs,
            self.max_num_tokens,
            self.cudagraph_mode,
            self.uniform_decode_query_len,
            use_uniform_decode_cudagraph,
        )

        self.graphs: dict[int, torch.cuda.CUDAGraph] = {}
        self.pool = None
        if self.cudagraph_mode != CUDAGraphMode.NONE:
            self.pool = torch.cuda.graph_pool_handle()
        self.hidden_states: torch.Tensor | None = None

    def needs_capture(self) -> bool:
        return len(self.cudagraph_sizes) > 0

    def get_cudagraph_size(
        self, num_tokens: int, uniform_decode: bool = False
    ) -> int | None:
        if uniform_decode and self.uniform_decode_cudagraph_sizes:
            return self.uniform_decode_cudagraph_sizes.get(num_tokens)
        return self.cudagraph_sizes.get(num_tokens)

    def capture_graph(
        self,
        num_tokens: int,
        capture_cg_mode: CUDAGraphMode,
        model: nn.Module,
        input_buffers: InputBuffers,
        mrope_positions: torch.Tensor | None,
        inputs_embeds: torch.Tensor | None,
        block_tables: BlockTables,
        attn_metadata_builders: list[AttentionMetadataBuilder],
        kv_cache_config: KVCacheConfig,
        has_lora: bool = False,
        uniform_decode: bool = False,
    ) -> None:
        # select and check capture function
        assert capture_cg_mode in [CUDAGraphMode.PIECEWISE, CUDAGraphMode.FULL], (
            f"Invalid capture_cudagraph_mode for capture: {capture_cg_mode}"
        )
        if capture_cg_mode == CUDAGraphMode.PIECEWISE:
            capture_fn = self._capture_piecewise_graph
        else:
            capture_fn = self._capture_full_graph
        # prepare inputs
        if uniform_decode:
            num_reqs = min(
                cdiv(num_tokens, self.uniform_decode_query_len),
                self.max_num_reqs,
            )
        else:
            num_reqs = min(num_tokens, self.max_num_reqs)
        input_ids = input_buffers.input_ids[:num_tokens]
        positions = input_buffers.positions[:num_tokens]
        if self.uses_mrope:
            assert mrope_positions is not None
            positions = mrope_positions[:, :num_tokens]
        if inputs_embeds is not None:
            inputs_embeds = inputs_embeds[:num_tokens]
        attn_metadata, slot_mappings = prepare_inputs_to_capture(
            num_reqs,
            num_tokens,
            input_buffers,
            block_tables,
            attn_metadata_builders,
            self.max_model_len,
            kv_cache_config,
            uniform_decode_query_len=(
                self.uniform_decode_query_len if uniform_decode else 0
            ),
        )
        num_tokens_across_dp = make_num_tokens_across_dp(self.dp_size, num_tokens)

        # Warm up.
        with set_forward_context(
            attn_metadata,
            self.vllm_config,
            num_tokens=num_tokens,
            cudagraph_runtime_mode=CUDAGraphMode.NONE,
            num_tokens_across_dp=num_tokens_across_dp,
            slot_mapping=slot_mappings,
        ):
            hidden_states = model(
                input_ids=input_ids,
                positions=positions,
                inputs_embeds=inputs_embeds,
            )
            if self.hidden_states is None:
                self.hidden_states = torch.empty_like(hidden_states)

        capture_fn(
            num_tokens=num_tokens,
            num_reqs=num_reqs,
            model=model,
            input_ids=input_ids,
            positions=positions,
            inputs_embeds=inputs_embeds,
            num_tokens_across_dp=num_tokens_across_dp,
            attn_metadata=attn_metadata,
            slot_mappings=slot_mappings,
            has_lora=has_lora,
        )

    def _capture_full_graph(
        self,
        num_tokens: int,
        num_reqs: int,
        model: nn.Module,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        inputs_embeds: torch.Tensor | None,
        num_tokens_across_dp: torch.Tensor,
        attn_metadata: dict[str, Any] | None,
        slot_mappings: dict[str, torch.Tensor] | None,
        has_lora: bool = False,
    ) -> None:
        assert attn_metadata is not None
        # Capture the graph.
        assert num_tokens not in self.graphs
        graph = torch.cuda.CUDAGraph()
        with (
            set_forward_context(
                attn_metadata=attn_metadata,
                vllm_config=self.vllm_config,
                num_tokens=num_tokens,
                cudagraph_runtime_mode=CUDAGraphMode.NONE,
                num_tokens_across_dp=num_tokens_across_dp,
                slot_mapping=slot_mappings,
            ),
            torch.cuda.graph(graph, self.pool),
        ):
            hidden_states = model(
                input_ids=input_ids,
                positions=positions,
                inputs_embeds=inputs_embeds,
            )
            assert self.hidden_states is not None
            self.hidden_states[:num_tokens] = hidden_states
        self.graphs[num_tokens] = graph

    def _capture_piecewise_graph(
        self,
        num_tokens: int,
        num_reqs: int,
        model: nn.Module,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        inputs_embeds: torch.Tensor | None,
        num_tokens_across_dp: torch.Tensor,
        attn_metadata: dict[str, Any] | None,
        slot_mappings: dict[str, torch.Tensor] | None,
        has_lora: bool = False,
    ) -> None:
        # create batch descriptor for piecewise cudagraph dispatch key
        batch_descriptor = BatchDescriptor(num_tokens=num_tokens, has_lora=has_lora)

        # Capture run - CUDAGraphWrapper inside torch.compile will auto capture.
        with set_forward_context(
            attn_metadata=None,  # piecewise no need attn_metadata
            vllm_config=self.vllm_config,
            num_tokens=num_tokens,
            cudagraph_runtime_mode=CUDAGraphMode.PIECEWISE,
            num_tokens_across_dp=num_tokens_across_dp,
            batch_descriptor=batch_descriptor,
            slot_mapping=slot_mappings,
        ):
            hidden_states = model(
                input_ids=input_ids,
                positions=positions,
                inputs_embeds=inputs_embeds,
            )
            assert self.hidden_states is not None
            self.hidden_states[:num_tokens] = hidden_states

    @torch.inference_mode()
    def capture(
        self,
        model: nn.Module,
        input_buffers: InputBuffers,
        mrope_positions: torch.Tensor | None,
        inputs_embeds: torch.Tensor | None,
        block_tables: BlockTables,
        attn_metadata_builders: list[AttentionMetadataBuilder],
        kv_cache_config: KVCacheConfig,
        has_lora: bool = False,
    ) -> None:
        common_kwargs = dict(
            device=self.device,
            capture_fn=self.capture_graph,
            model=model,
            input_buffers=input_buffers,
            mrope_positions=mrope_positions,
            inputs_embeds=inputs_embeds,
            block_tables=block_tables,
            attn_metadata_builders=attn_metadata_builders,
            kv_cache_config=kv_cache_config,
            has_lora=has_lora,
        )

        # Phase 1: Capture for mixed prefill-decode batches if needed.
        mixed_mode = self.cudagraph_mode.mixed_mode()
        if mixed_mode != CUDAGraphMode.NONE:
            capture_graphs(
                cudagraph_sizes=self.cudagraph_sizes,
                capture_cudagraph_mode=mixed_mode,
                desc=f"Capturing CUDA graphs (mixed, {mixed_mode.name})",
                uniform_decode=False,
                **common_kwargs,
            )

        # Phase 2: Capture FULL graphs for uniform decode batches if needed.
        # This is only needed if we use a separate routine for decode batches
        # and the decode_mode is FULL.
        if self.uniform_decode_cudagraph_sizes:
            capture_graphs(
                cudagraph_sizes=self.uniform_decode_cudagraph_sizes,
                capture_cudagraph_mode=CUDAGraphMode.FULL,
                desc="Capturing CUDA graphs (decode, FULL)",
                uniform_decode=True,
                **common_kwargs,
            )

    def get_cudagraph_runtime_mode(
        self, num_reqs: int, num_tokens: int, max_query_len: int
    ) -> tuple[CUDAGraphMode, int | None]:
        is_uniform_decode = (max_query_len == self.uniform_decode_query_len) and (
            num_tokens == max_query_len * num_reqs
        )

        cudagraph_size = self.get_cudagraph_size(num_tokens, is_uniform_decode)
        if cudagraph_size is None:
            cudagraph_mode = CUDAGraphMode.NONE
        elif is_uniform_decode:
            cudagraph_mode = self.cudagraph_mode.decode_mode()
        else:
            cudagraph_mode = self.cudagraph_mode.mixed_mode()
        return cudagraph_mode, cudagraph_size

    def run_fullgraph(self, num_tokens: int) -> torch.Tensor:
        assert num_tokens in self.graphs, f"No cudagraph for {num_tokens} tokens"
        self.graphs[num_tokens].replay()
        assert self.hidden_states is not None
        return self.hidden_states[:num_tokens]


def get_cudagraph_sizes(
    capture_sizes: list[int] | None,
    max_num_reqs: int,
    max_num_tokens: int,
    cudagraph_mode: CUDAGraphMode,
    uniform_decode_query_len: int = 1,
    uniform_decode_cudagraph: bool = False,
) -> tuple[dict[int, int], dict[int, int]]:
    # Support both FULL and PIECEWISE cudagraph modes
    if cudagraph_mode == CUDAGraphMode.NONE:
        return {}, {}
    if not capture_sizes:
        return {}, {}

    capture_sizes = sorted(capture_sizes)
    if not capture_sizes:
        return {}, {}

    cudagraph_sizes: dict[int, int] = {}
    for i in range(1, capture_sizes[-1] + 1):
        for x in capture_sizes:
            if i <= x:
                cudagraph_sizes[i] = x
                break

    uniform_decode_cudagraph_sizes: dict[int, int] = {}
    if uniform_decode_cudagraph:
        max_num_tokens = max_num_reqs * uniform_decode_query_len
        uniform_decode_cudagraph_sizes = {
            k: v
            for k, v in cudagraph_sizes.items()
            if v <= max_num_tokens and v >= uniform_decode_query_len
        }
    return cudagraph_sizes, uniform_decode_cudagraph_sizes


def capture_graphs(
    cudagraph_sizes: dict[int, int],
    device: torch.device,
    capture_fn: Callable,
    capture_cudagraph_mode: CUDAGraphMode,
    desc: str = "Capturing CUDA graphs",
    **capture_kwargs,
) -> None:
    # Capture larger graphs first.
    sizes_to_capture = sorted(set(cudagraph_sizes.values()), reverse=True)
    if is_global_first_rank():
        sizes_to_capture = tqdm(sizes_to_capture, desc=desc)

    with graph_capture(device=device):
        for size in sizes_to_capture:
            capture_fn(size, capture_cudagraph_mode, **capture_kwargs)


def prepare_inputs_to_capture(
    num_reqs: int,
    num_tokens: int,
    input_buffers: InputBuffers,
    block_tables: BlockTables,
    attn_metadata_builders: list[AttentionMetadataBuilder],
    max_model_len: int,
    kv_cache_config: KVCacheConfig,
    uniform_decode_query_len: int = 0,
) -> tuple[dict[str, Any], dict[str, torch.Tensor]]:
    if uniform_decode_query_len > 0:
        num_tokens_per_req = uniform_decode_query_len
    else:
        num_tokens_per_req = num_tokens // num_reqs

    query_start_loc_np = np.arange(num_reqs + 1, dtype=np.int32) * num_tokens_per_req
    query_start_loc_np[-1] = num_tokens
    query_start_loc_cpu = torch.from_numpy(query_start_loc_np)
    input_buffers.query_start_loc[: num_reqs + 1] = query_start_loc_cpu
    input_buffers.query_start_loc[num_reqs + 1 :] = num_tokens
    query_start_loc = input_buffers.query_start_loc[: num_reqs + 1]

    # HACK(woosuk): For faster warmup, we set seq_lens (GPU) to num_tokens
    # rather than max_model_len.
    input_buffers.seq_lens[:num_reqs] = num_tokens
    input_buffers.seq_lens[num_reqs:] = 0

    input_buffers.dcp_local_seq_lens[:num_reqs] = num_tokens
    input_buffers.dcp_local_seq_lens[num_reqs:] = 0

    input_block_tables = [x[:num_reqs] for x in block_tables.input_block_tables]
    slot_mappings = block_tables.slot_mappings[:, :num_tokens]
    slot_mappings_by_layer = build_slot_mappings_by_layer(
        slot_mappings, kv_cache_config
    )

    attn_metadata = build_attn_metadata(
        attn_metadata_builders=attn_metadata_builders,
        num_reqs=num_reqs,
        num_tokens=num_tokens,
        query_start_loc_gpu=query_start_loc,
        query_start_loc_cpu=query_start_loc_cpu,
        max_query_len=num_tokens_per_req,
        seq_lens=input_buffers.seq_lens,
        max_seq_len=max_model_len,
        block_tables=input_block_tables,
        slot_mappings=slot_mappings,
        kv_cache_config=kv_cache_config,
        dcp_local_seq_lens=input_buffers.dcp_local_seq_lens,
    )
    return attn_metadata, slot_mappings_by_layer