system_allocator.h

/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.

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 <stddef.h>    // for size_t
#include <sys/mman.h>  // for mlock and munlock
#include <cstdlib>     // for malloc and free

#include <gflags/gflags.h>
#include "paddle/platform/assert.h"
#include "paddle/platform/cuda.h"

DEFINE_bool(uses_pinned_memory, false,
            "If set, allocate cpu/gpu pinned memory.");

namespace paddle {
namespace memory {
namespace detail {

// If uses_pinned_memory is true, CPUAllocator calls mlock, which
// returns pinned and locked memory as staging areas for data exchange
// between host and device.  Allocates too much would reduce the amount
// of memory available to the system for paging.  So, by default, we
// should set false to uses_pinned_memory.
class CPUAllocator {
 public:
  static void* Alloc(size_t size) {
    void* p = std::malloc(size);
    if (p != nullptr && FLAGS_uses_pinned_memory) {
      mlock(p, size);
    }
    return p;
  }

  static void Free(void* p, size_t size) {
    if (p != nullptr && FLAGS_uses_pinned_memory) {
      munlock(p, size);
    }
    std::free(p);
  }
};

#ifndef PADDLE_ONLY_CPU  // The following code are for CUDA.

// GPUAllocator<staging=true> calls cudaHostMalloc, which returns
// pinned and locked memory as staging areas for data exchange
// between host and device.  Allocates too much would reduce the
// amount of memory available to the system for paging.  So, by
// default, we should use GPUAllocator<staging=false>.
class GPUAllocator {
 public:
  static void* Alloc(size_t size) {
    void* p = 0;
    cudaError_t result = FLAGS_uses_pinned_memory ? cudaMallocHost(&p, size)
                                                  : cudaMalloc(&p, size);
    if (result != cudaSuccess) {
      cudaGetLastError();  // clear error if there is any.
    }
    return result == cudaSuccess ? p : nullptr;
  }

  static void Free(void* p, size_t size) {
    // Purposefully allow cudaErrorCudartUnloading, because
    // that is returned if you ever call cudaFree after the
    // driver has already shutdown. This happens only if the
    // process is terminating, in which case we don't care if
    // cudaFree succeeds.
    cudaError_t err = FLAGS_uses_pinned_memory ? cudaFreeHost(p) : cudaFree(p);
    if (err != cudaErrorCudartUnloading) {
      platform::throw_on_error(err, "cudaFree{Host} failed");
    }
  }
};

#endif  // PADDLE_ONLY_CPU

}  // namespace detail
}  // namespace memory
}  // namespace paddle