managed_memory_resource.hpp

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/*
 * SPDX-FileCopyrightText: Copyright (c) 2019-2026, NVIDIA CORPORATION.
 * SPDX-License-Identifier: Apache-2.0
 */
#pragma once
 
#include <rmm/aligned.hpp>
#include <rmm/detail/error.hpp>
#include <rmm/detail/export.hpp>
 
#include <cuda/memory_resource>
#include <cuda/stream_ref>
 
#include <cstddef>
 
namespace RMM_NAMESPACE {
namespace mr {
class managed_memory_resource final {
 public:
  managed_memory_resource()                               = default;
  ~managed_memory_resource()                              = default;
  managed_memory_resource(managed_memory_resource const&) = default;  
  managed_memory_resource(managed_memory_resource&&)      = default;  
  managed_memory_resource& operator=(managed_memory_resource const&) =
    default;  
  managed_memory_resource& operator=(managed_memory_resource&&) =
    default;  
 
  void* allocate([[maybe_unused]] cuda::stream_ref stream,
                 std::size_t bytes,
                 [[maybe_unused]] std::size_t alignment = rmm::CUDA_ALLOCATION_ALIGNMENT)
  {
    // FIXME: Unlike cudaMalloc, cudaMallocManaged will throw an error for 0
    // size allocations.
    if (bytes == 0) { return nullptr; }
 
    void* ptr{nullptr};
    RMM_CUDA_TRY_ALLOC(cudaMallocManaged(&ptr, bytes), bytes);
    return ptr;
  }
 
  void deallocate([[maybe_unused]] cuda::stream_ref stream,
                  void* ptr,
                  [[maybe_unused]] std::size_t bytes,
                  [[maybe_unused]] std::size_t alignment = rmm::CUDA_ALLOCATION_ALIGNMENT) noexcept
  {
    RMM_ASSERT_CUDA_SUCCESS_SAFE_SHUTDOWN(cudaFree(ptr));
  }
 
  void* allocate_sync(std::size_t bytes, std::size_t alignment = rmm::CUDA_ALLOCATION_ALIGNMENT)
  {
    auto* ptr = allocate(cuda::stream_ref{cudaStream_t{nullptr}}, bytes, alignment);
    RMM_CUDA_TRY(cudaStreamSynchronize(cudaStream_t{nullptr}));
    return ptr;
  }
 
  void deallocate_sync(void* ptr,
                       std::size_t bytes,
                       std::size_t alignment = rmm::CUDA_ALLOCATION_ALIGNMENT) noexcept
  {
    deallocate(cuda::stream_ref{cudaStream_t{nullptr}}, ptr, bytes, alignment);
  }
 
  RMM_CONSTEXPR_FRIEND void get_property(managed_memory_resource const&,
                                         cuda::mr::device_accessible) noexcept
  {
  }
 
  RMM_CONSTEXPR_FRIEND void get_property(managed_memory_resource const&,
                                         cuda::mr::host_accessible) noexcept
  {
  }
 
  [[nodiscard]] bool operator==(managed_memory_resource const&) const noexcept { return true; }
 
  [[nodiscard]] bool operator!=(managed_memory_resource const&) const noexcept { return false; }
};
 
// static property checks
static_assert(cuda::mr::synchronous_resource<managed_memory_resource>);
static_assert(cuda::mr::resource<managed_memory_resource>);
static_assert(
  cuda::mr::synchronous_resource_with<managed_memory_resource, cuda::mr::device_accessible>);
static_assert(
  cuda::mr::synchronous_resource_with<managed_memory_resource, cuda::mr::host_accessible>);
static_assert(cuda::mr::resource_with<managed_memory_resource, cuda::mr::device_accessible>);
static_assert(cuda::mr::resource_with<managed_memory_resource, cuda::mr::host_accessible>);
  // end of group
}  // namespace mr
}  // namespace RMM_NAMESPACE