net_async_scheduling.cc

#include "caffe2/core/net_async_scheduling.h"

#include "caffe2/core/net_async_tracing.h"

namespace caffe2 {

AsyncSchedulingNet::AsyncSchedulingNet(
    const std::shared_ptr<const NetDef>& net_def,
    Workspace* ws)
    : AsyncNetBase(net_def, ws), running_(false) {}

void AsyncSchedulingNet::reset() {
  AsyncNetBase::reset();
  processed_tasks_num_ = 0;
}

void AsyncSchedulingNet::Wait() {
  std::unique_lock<std::mutex> lock(running_mutex_);
  while (running_) {
    running_cv_.wait(lock);
  }
}

bool AsyncSchedulingNet::isInlineTask(int parent_id, int child_id) const {
  if (!options_.use_dfs_scheduling_) {
    return false;
  }
  const auto* last_parent_op = lastTaskOp(parent_id);
  const auto* first_child_op = firstTaskOp(child_id);
  // check that we do not cross device boundary
  return IsSameDevice(
      last_parent_op->device_option(), first_child_op->device_option());
}

// schedule() is not supposed to throw, all exceptions in the ops are caught
// and reported in the end of the graph's execution, the full graph of tasks
// is expected to be scheduled
void AsyncSchedulingNet::schedule(int task_id, bool run_inline) noexcept {
  if (!testAndSetScheduled(task_id)) {
    return;
  }
  auto schedule_func = [this, task_id]() {
    try {
      if (success_) {
        int stream_id = 0;
        if (options_.streams_per_gpu_ > 1) {
          try {
            stream_id = stream(task_id);
          } catch (const std::exception& e) {
            C10_LOG_EVERY_MS(ERROR, 1000)
                << "Failed to select a stream: " << e.what();
          }
        }
        if (!run(task_id, stream_id)) {
          success_ = false;
        }
      }

      if (options_.report_stats_) {
        try {
          auto last_op_id = lastTaskOpId(task_id);
          auto* last_op = lastTaskOp(task_id);
          if (last_op->device_option().device_type() == PROTO_CPU &&
              last_op->HasAsyncPart()) {
            last_op->event().SetCallback([this, last_op_id] {
              counters_.AddPerOpAsyncEndTime(last_op_id);
            });
          }
        } catch (const std::exception& e) {
          C10_LOG_EVERY_MS(ERROR, 1000)
              << "Failed to report operator stats: " << e.what();
        }
      }

      for (auto child_id : children(task_id)) {
        int parent_count = updateParentCount(child_id);
        if (parent_count == 0) {
          // Schedule a child if:
          // - there is failure, we skip an op execution and finish the job
          // - forced scheduling though always_schedule_child_
          // - finish_chain_ is set, in this case parents are
          //   guaranteed to be finished
          // - in all other cases, check parents with canSchedule
          if (!success_ || options_.always_schedule_child_ ||
              options_.finish_chain_ || canSchedule(child_id)) {
            // if DFS scheduling is enabled, run children inline,
            // ignore DFS scheduling in callbacks
            schedule(child_id, isInlineTask(task_id, child_id));
          } else {
            bool parent_failed = false;
            bool parent_needs_polling = false;
            std::vector<int> parents_with_callback;

            for (auto parent_id : parents(child_id)) {
              auto& parent_event = event(parent_id);
              auto parent_status = parent_event.Query();

              if (parent_status == EventStatus::EVENT_FAILED) {
                parent_failed = true;
                break;
              } else if (parent_status == EventStatus::EVENT_SCHEDULED) {
                // parent is not finished yet, check if this is blocking us
                // from scheduling a child
                if (!canSchedule(parent_id, child_id)) {
                  // we can't schedule a child because of this parent,
                  // check if parent supports callback
                  if (parent_event.SupportsCallback()) {
                    parents_with_callback.push_back(parent_id);
                  } else {
                    parent_needs_polling = true;
                    break;
                  }
                }
              } else if (parent_status != EventStatus::EVENT_SUCCESS) {
                VLOG(1) << "Unexpected parent task state: " << parent_status
                        << ", task id: " << child_id
                        << ", parent task id: " << parent_id;
                parent_failed = true;
                break;
              }
            }

            if (parent_failed) {
              // one of parents failed, set failure flag and wrap up execution
              success_ = false;
              schedule(child_id, isInlineTask(task_id, child_id));
            } else if (parent_needs_polling) {
              // some parents are blocking us from scheduling a child and don't
              // support callbacks, using polling
              const auto& child_device_option =
                  event(child_id).GetDeviceOption();
              pool(child_device_option)
                  ->run(std::bind(
                      &AsyncSchedulingNet::pollAndSchedule, this, child_id));
            } else if (!parents_with_callback.empty()) {
              // some parents are blocking us from scheduling a child and they
              // support callbacks
              for (auto parent_id : parents_with_callback) {
                event(parent_id).SetCallback(std::bind(
                    &AsyncSchedulingNet::parentCallback, this, parent_id));
              }
            } else {
              // we're ready to schedule a child
              schedule(child_id, isInlineTask(task_id, child_id));
            }
          }
        }
      }

      // In case of net's failure, make sure all pending tasks are finished
      if (!success_) {
        CancelAndFinishAsyncTasks();
      }

      // finishRun may cause waiters to wake up and destroy the net,
      // before we call finishRun we need to make sure all other (finishing)
      // tasks are done;
      // Bumping and checking the counter after the task's job is done
      auto tasks_num = tasksNum();
      auto cur_processed_tasks = ++processed_tasks_num_;
      if (cur_processed_tasks == tasks_num) {
        finishRun();
      }
    } catch (const std::exception& e) {
      // error of core scheduling and/or logic, will call terminate
      LOG(FATAL) << "Unexpected error during graph scheduling run: "
                 << e.what();
    } catch (...) {
      LOG(FATAL) << "Unknown error during graph scheduling run";
    }
  };

  if (run_inline) {
    schedule_func();
  } else {
    const auto& device_option = event(task_id).GetDeviceOption();
    pool(device_option)->run(schedule_func);
  }
}

void AsyncSchedulingNet::parentCallback(int parent_id) {
  if (event(parent_id).Query() != EventStatus::EVENT_SUCCESS) {
    success_ = false;
  }
  for (auto child_id : children(parent_id)) {
    int parent_count = getParentCount(child_id);
    if (parent_count == 0) {
      if (!success_ || canSchedule(child_id)) {
        schedule(child_id);
      }
    }
  }
}

void AsyncSchedulingNet::pollAndSchedule(int task_id) {
  bool parent_failed = false;
  bool can_schedule = canSchedule(task_id, nullptr, &parent_failed);
  if (parent_failed) {
    success_ = false;
  }
  // schedule the task if:
  //  - parents are ready
  //  - we failed / cleanup started (no ops will run)

  if (can_schedule || !success_ || parent_failed) {
    schedule(task_id);
  } else {
    const auto& device_option = event(task_id).GetDeviceOption();
    pool(device_option)
        ->run(std::bind(&AsyncSchedulingNet::pollAndSchedule, this, task_id));
  }
}

void AsyncSchedulingNet::finishRun() {
  std::unique_lock<std::mutex> lock(running_mutex_);
  // wait for scheduled ops and make sure all events are marked as finished
  finalizeEvents();
  if (options_.report_stats_) {
    counters_.ReportRunEnd();
  }
  // notify observers and waiters
  StopAllObservers();
  running_ = false;
  running_cv_.notify_all();
}

bool AsyncSchedulingNet::RunAsync() {
  try {
    std::unique_lock<std::mutex> lock(running_mutex_);
    if (running_) {
      LOG(ERROR) << "Detected concurrent runs";
      return false;
    }
    running_ = true;
    reset();

    StartAllObservers();
    tracing::startIter(tracer_);
    if (options_.report_stats_) {
      counters_.ReportRunStart();
    }
  } catch (const std::exception& e) {
    LOG(ERROR) << "Exception while starting an async run: " << e.what();
    finishRun();
    throw;
  } catch (...) {
    LOG(ERROR) << "Exception while starting an async run: unknown error";
    finishRun();
    throw;
  }

  // schedule() is not expected to throw, at this moment all the initial tasks
  // will be scheduled and the full graph of tasks will be executed
  for (auto task_id = 0; task_id < tasksNum(); ++task_id) {
    if (parents(task_id).empty()) {
      schedule(task_id, options_.run_root_tasks_inline_);
    }
  }

  if (tasksNum() == 0) {
    finishRun();
  }

  if (options_.is_blocking_) {
    Wait();
  }

  return true;
}

void AsyncSchedulingNet::Cancel() {
  success_ = false;
  CancelAndFinishAsyncTasks();
}

void AsyncSchedulingNet::CancelAndFinishAsyncTasks() {
  for (auto tid = 0; tid < tasksNum(); ++tid) {
    if (event(tid).Query() == EventStatus::EVENT_SCHEDULED) {
      // SetFinished may throw, e.g. when we call it on already finished
      // event, and in some other cases (CUDA)
      try {
        lastTaskOp(tid)->CancelAsyncCallback();

        // throw and catch exception to preserve stack trace
        try {
          throw AsyncNetCancelled();
        } catch (const AsyncNetCancelled& e) {
          event(tid).SetFinishedWithException(e.what());
        }
      } catch (const EnforceNotMet&) {
        // ignore
      }
    }
  }
}

AsyncSchedulingNet::~AsyncSchedulingNet() {
  Wait();
}

REGISTER_NET(async_scheduling, AsyncSchedulingNet);

} // namespace caffe2