stream.hpp

/*
 * Copyright (c) 2023-2024, NVIDIA CORPORATION.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once
 
#include <sys/types.h>
#include <algorithm>
#include <cstdlib>
#include <kvikio/error.hpp>
#include <kvikio/shim/cuda.hpp>
#include <kvikio/shim/cufile.hpp>
#include <tuple>
 
namespace kvikio {
 
class StreamFuture {
 private:
  struct ArgByVal {
    std::size_t size;
    off_t file_offset;
    off_t devPtr_offset;
    ssize_t bytes_done;
  };
 
  void* _devPtr_base{nullptr};
  CUstream _stream{nullptr};
  ArgByVal* _val{nullptr};
  bool _stream_synchronized{false};
 
 public:
  StreamFuture() noexcept = default;
 
  StreamFuture(
    void* devPtr_base, std::size_t size, off_t file_offset, off_t devPtr_offset, CUstream stream)
    : _devPtr_base{devPtr_base}, _stream{stream}
  {
    // Notice, we allocate the arguments using malloc() as specified in the cuFile docs:
    // <https://docs.nvidia.com/gpudirect-storage/api-reference-guide/index.html#cufilewriteasync>
    if ((_val = static_cast<ArgByVal*>(std::malloc(sizeof(ArgByVal)))) == nullptr) {
      throw std::bad_alloc{};
    }
    *_val = {
      .size = size, .file_offset = file_offset, .devPtr_offset = devPtr_offset, .bytes_done = 0};
  }
 
  StreamFuture(const StreamFuture&)        = delete;
  StreamFuture& operator=(StreamFuture& o) = delete;
  StreamFuture(StreamFuture&& o) noexcept
    : _devPtr_base{std::exchange(o._devPtr_base, nullptr)},
      _stream{std::exchange(o._stream, nullptr)},
      _val{std::exchange(o._val, nullptr)},
      _stream_synchronized{o._stream_synchronized}
  {
  }
  StreamFuture& operator=(StreamFuture&& o) noexcept
  {
    _devPtr_base         = std::exchange(o._devPtr_base, nullptr);
    _stream              = std::exchange(o._stream, nullptr);
    _val                 = std::exchange(o._val, nullptr);
    _stream_synchronized = o._stream_synchronized;
    return *this;
  }
 
  std::tuple<void*, std::size_t*, off_t*, off_t*, ssize_t*, CUstream> get_args() const
  {
    if (_val == nullptr) {
      throw kvikio::CUfileException("cannot get arguments from an uninitialized StreamFuture");
    }
    return {_devPtr_base,
            &_val->size,
            &_val->file_offset,
            &_val->devPtr_offset,
            &_val->bytes_done,
            _stream};
  }
 
  std::size_t check_bytes_done()
  {
    if (_val == nullptr) {
      throw kvikio::CUfileException("cannot check bytes done on an uninitialized StreamFuture");
    }
 
    if (!_stream_synchronized) {
      _stream_synchronized = true;
      CUDA_DRIVER_TRY(cudaAPI::instance().StreamSynchronize(_stream));
    }
 
    CUFILE_CHECK_BYTES_DONE(_val->bytes_done);
    // At this point, we know `_val->bytes_done` is a positive value otherwise
    // CUFILE_CHECK_BYTES_DONE() would have raised an exception.
    return static_cast<std::size_t>(_val->bytes_done);
  }
 
  ~StreamFuture() noexcept
  {
    if (_val != nullptr) {
      try {
        check_bytes_done();
      } catch (const kvikio::CUfileException& e) {
        std::cerr << e.what() << std::endl;
      }
      std::free(_val);
    }
  }
};
 
}  // namespace kvikio