EVOLUTION-MANAGER

Edit File: xla_device_context.h

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
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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,
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See the License for the specific language governing permissions and
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==============================================================================*/

#ifndef TENSORFLOW_COMPILER_JIT_XLA_DEVICE_CONTEXT_H_
#define TENSORFLOW_COMPILER_JIT_XLA_DEVICE_CONTEXT_H_

#include <memory>

#include "absl/synchronization/mutex.h"
#include "tensorflow/compiler/jit/xla_tensor.h"
#include "tensorflow/compiler/tf2xla/xla_compiler.h"
#include "tensorflow/compiler/xla/client/global_data.h"
#include "tensorflow/compiler/xla/client/local_client.h"
#include "tensorflow/core/framework/allocator.h"
#include "tensorflow/core/framework/device_base.h"
#include "tensorflow/core/lib/core/status.h"

namespace tensorflow {

// The allocator used for Tensors assigned to the XLA device. The allocator
// ignores the alignment and size of the request and always returns a new,
// empty, XlaTensor.
class XlaDeviceAllocator : public Allocator {
 public:
  XlaDeviceAllocator(se::StreamExecutor* stream_executor);
  ~XlaDeviceAllocator() override;

string Name() override;

void* AllocateRaw(size_t alignment, size_t num_bytes) override;
  void DeallocateRaw(void* ptr) override;
  absl::optional<AllocatorStats> GetStats() override;

private:
  // The stream executor of the device.
  se::StreamExecutor* stream_executor_;
};

// Helper class for managing data transfers between host and XLA devices.
class XlaDeviceContext : public DeviceContext {
 public:
  explicit XlaDeviceContext(
      std::shared_ptr<se::Stream> compute_stream,
      std::shared_ptr<se::Stream> host_to_device_stream,
      std::shared_ptr<se::Stream> device_to_host_stream,
      std::vector<std::shared_ptr<se::Stream>> device_to_device_streams,
      xla::LocalClient* client,
      XlaCompiler::ShapeRepresentationFn shape_representation_fn,
      thread::ThreadPool* thread_pool, bool use_fast_mem = false);

void CopyCPUTensorToDevice(const Tensor* cpu_tensor, Device* device,
                             Tensor* device_tensor, StatusCallback done,
                             bool sync_dst_compute) const override;
  void CopyDeviceTensorToCPU(const Tensor* device_tensor,
                             absl::string_view tensor_name, Device* device,
                             Tensor* cpu_tensor, StatusCallback done) override;
  void CopyTensorInSameDevice(const Tensor* input_tensor, Device* device,
                              Tensor* output_tensor,
                              StatusCallback done) const override;

xla::LocalClient* client() const { return client_; }
  se::Stream* stream() const override { return stream_.get(); }
  se::Stream* host_to_device_stream() const {
    return host_to_device_stream_.get();
  }
  se::Stream* device_to_device_stream(int index) const {
    return device_to_device_streams_.at(index).get();
  }
  xla::TransferManager* transfer_manager() const { return transfer_manager_; }
  const XlaCompiler::ShapeRepresentationFn& shape_representation_fn() const {
    return shape_representation_fn_;
  }

// Returns a device-to-device stream, in round-robin fashion.
  se::Stream* GetDeviceToDeviceStream();

Status ThenExecute(Device* device, stream_executor::Stream* stream,
                     std::function<void()> func) override;

private:
  bool UseMultipleStreams() const { return stream_ != host_to_device_stream_; }

// The main compute stream of the device, used to synchronize the transfer
  // streams if they are set.
  std::shared_ptr<se::Stream> stream_;
  // The stream to use for transferring data from host to device. Can be
  // idential to stream_, but must not be nullptr.
  std::shared_ptr<se::Stream> host_to_device_stream_;
  // The stream to use for transferring data from device to host. Can be
  // idential to stream_. If nullptr, borrow a stream from backend for each
  // transfer request to support out-of-order requests.
  std::shared_ptr<se::Stream> device_to_host_stream_;
  // Streams to use for transferring data directly between different devices,
  // e.g., over NVLINK.
  std::vector<std::shared_ptr<se::Stream>> device_to_device_streams_;

// For the underlying memory allocator and XLA's TransferManager.
  xla::LocalClient* client_;
  // Transfer manager, for marshalling data to and from the device.
  xla::TransferManager* transfer_manager_;

XlaCompiler::ShapeRepresentationFn shape_representation_fn_;

// Thread pool used for running closures
  thread::ThreadPool* thread_pool_;

// Whether uses TPU fast mem or not.
  bool use_fast_mem_;

absl::Mutex mu_;
  int next_stream_ TF_GUARDED_BY(mu_) = 0;
};

}  // namespace tensorflow

#endif  // TENSORFLOW_COMPILER_JIT_XLA_DEVICE_CONTEXT_H_