cuda_wrapper.py

"""This file is a pure Python wrapper for the cudart library.
It avoids the need to compile a separate shared library, and is
convenient for use when we just need to call a few functions.
"""

import ctypes
import glob
import os
import sys
from dataclasses import dataclass
from typing import Any, Dict, List, Optional

# this line makes it possible to directly load `libcudart.so` using `ctypes`
import torch  # noqa

from vllm.logger import init_logger

logger = init_logger(__name__)

# === export types and functions from cudart to Python ===
# for the original cudart definition, please check
# https://docs.nvidia.com/cuda/cuda-runtime-api/index.html

cudaError_t = ctypes.c_int
cudaMemcpyKind = ctypes.c_int


class cudaIpcMemHandle_t(ctypes.Structure):
    _fields_ = [("internal", ctypes.c_byte * 128)]


@dataclass
class Function:
    name: str
    restype: Any
    argtypes: List[Any]


def get_pytorch_default_cudart_library_path() -> str:
    # code borrowed from https://github.com/pytorch/pytorch/blob/1cae60a87e5bdda8bcf55724a862eeed98a9747e/torch/__init__.py#L284 # noqa
    lib_folder = "cuda_runtime"
    lib_name = "libcudart.so.*[0-9]"
    lib_path = None
    for path in sys.path:
        nvidia_path = os.path.join(path, "nvidia")
        if not os.path.exists(nvidia_path):
            continue
        candidate_lib_paths = glob.glob(
            os.path.join(nvidia_path, lib_folder, "lib", lib_name))
        if candidate_lib_paths and not lib_path:
            lib_path = candidate_lib_paths[0]
        if lib_path:
            break
    if not lib_path:
        raise ValueError(f"{lib_name} not found in the system path {sys.path}")
    return lib_path


class CudaRTLibrary:
    exported_functions = [
        # ​cudaError_t cudaSetDevice ( int  device )
        Function("cudaSetDevice", cudaError_t, [ctypes.c_int]),
        # cudaError_t 	cudaDeviceSynchronize ( void )
        Function("cudaDeviceSynchronize", cudaError_t, []),
        # ​cudaError_t cudaDeviceReset ( void )
        Function("cudaDeviceReset", cudaError_t, []),

        # const char* 	cudaGetErrorString ( cudaError_t error )
        Function("cudaGetErrorString", ctypes.c_char_p, [cudaError_t]),

        # ​cudaError_t 	cudaMalloc ( void** devPtr, size_t size )
        Function("cudaMalloc", cudaError_t,
                 [ctypes.POINTER(ctypes.c_void_p), ctypes.c_size_t]),
        # ​cudaError_t 	cudaFree ( void* devPtr )
        Function("cudaFree", cudaError_t, [ctypes.c_void_p]),
        # ​cudaError_t cudaMemset ( void* devPtr, int  value, size_t count )
        Function("cudaMemset", cudaError_t,
                 [ctypes.c_void_p, ctypes.c_int, ctypes.c_size_t]),
        # ​cudaError_t cudaMemcpy ( void* dst, const void* src, size_t count, cudaMemcpyKind kind ) # noqa
        Function("cudaMemcpy", cudaError_t, [
            ctypes.c_void_p, ctypes.c_void_p, ctypes.c_size_t, cudaMemcpyKind
        ]),

        # cudaError_t cudaIpcGetMemHandle ( cudaIpcMemHandle_t* handle, void* devPtr ) # noqa
        Function("cudaIpcGetMemHandle", cudaError_t,
                 [ctypes.POINTER(cudaIpcMemHandle_t), ctypes.c_void_p]),
        # ​cudaError_t cudaIpcOpenMemHandle ( void** devPtr, cudaIpcMemHandle_t handle, unsigned int  flags ) # noqa
        Function("cudaIpcOpenMemHandle", cudaError_t, [
            ctypes.POINTER(ctypes.c_void_p), cudaIpcMemHandle_t, ctypes.c_uint
        ]),
    ]

    # class attribute to store the mapping from the path to the library
    # to avoid loading the same library multiple times
    path_to_library_cache: Dict[str, Any] = {}

    # class attribute to store the mapping from library path
    #  to the corresponding dictionary
    path_to_dict_mapping: Dict[str, Dict[str, Any]] = {}

    def __init__(self, so_file: Optional[str] = None):
        if so_file is None:
            so_file = get_pytorch_default_cudart_library_path()
        if so_file not in CudaRTLibrary.path_to_library_cache:
            lib = ctypes.CDLL(so_file)
            CudaRTLibrary.path_to_library_cache[so_file] = lib
        self.lib = CudaRTLibrary.path_to_library_cache[so_file]

        if so_file not in CudaRTLibrary.path_to_dict_mapping:
            _funcs = {}
            for func in CudaRTLibrary.exported_functions:
                f = getattr(self.lib, func.name)
                f.restype = func.restype
                f.argtypes = func.argtypes
                _funcs[func.name] = f
            CudaRTLibrary.path_to_dict_mapping[so_file] = _funcs
        self.funcs = CudaRTLibrary.path_to_dict_mapping[so_file]

    def CUDART_CHECK(self, result: cudaError_t) -> None:
        if result != 0:
            error_str = self.cudaGetErrorString(result)
            raise RuntimeError(f"CUDART error: {error_str}")

    def cudaGetErrorString(self, error: cudaError_t) -> str:
        return self.funcs["cudaGetErrorString"](error).decode("utf-8")

    def cudaSetDevice(self, device: int) -> None:
        self.CUDART_CHECK(self.funcs["cudaSetDevice"](device))

    def cudaDeviceSynchronize(self) -> None:
        self.CUDART_CHECK(self.funcs["cudaDeviceSynchronize"]())

    def cudaDeviceReset(self) -> None:
        self.CUDART_CHECK(self.funcs["cudaDeviceReset"]())

    def cudaMalloc(self, size: int) -> ctypes.c_void_p:
        devPtr = ctypes.c_void_p()
        self.CUDART_CHECK(self.funcs["cudaMalloc"](ctypes.byref(devPtr), size))
        return devPtr

    def cudaFree(self, devPtr: ctypes.c_void_p) -> None:
        self.CUDART_CHECK(self.funcs["cudaFree"](devPtr))

    def cudaMemset(self, devPtr: ctypes.c_void_p, value: int,
                   count: int) -> None:
        self.CUDART_CHECK(self.funcs["cudaMemset"](devPtr, value, count))

    def cudaMemcpy(self, dst: ctypes.c_void_p, src: ctypes.c_void_p,
                   count: int) -> None:
        cudaMemcpyDefault = 4
        kind = cudaMemcpyDefault
        self.CUDART_CHECK(self.funcs["cudaMemcpy"](dst, src, count, kind))

    def cudaIpcGetMemHandle(self,
                            devPtr: ctypes.c_void_p) -> cudaIpcMemHandle_t:
        handle = cudaIpcMemHandle_t()
        self.CUDART_CHECK(self.funcs["cudaIpcGetMemHandle"](
            ctypes.byref(handle), devPtr))
        return handle

    def cudaIpcOpenMemHandle(self,
                             handle: cudaIpcMemHandle_t) -> ctypes.c_void_p:
        cudaIpcMemLazyEnablePeerAccess = 1
        devPtr = ctypes.c_void_p()
        self.CUDART_CHECK(self.funcs["cudaIpcOpenMemHandle"](
            ctypes.byref(devPtr), handle, cudaIpcMemLazyEnablePeerAccess))
        return devPtr