text: /*
   * Copyright (C) 2016 The Android Open Source Project
   *
   * 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.
   */
  #include "perfd/cpu/cpu_collector.h"
  
  #include <unistd.h>
  #include <atomic>
  #include <thread>
  
  #include "utils/clock.h"
  #include "utils/stopwatch.h"
  #include "utils/thread_name.h"
  #include "utils/trace.h"
  
  namespace profiler {
  
  CpuCollector::~CpuCollector() {
    if (is_running_.load()) {
      Stop();
    }
  }
  
  void CpuCollector::Start() {
    if (!is_running_.exchange(true)) {
      sampler_thread_ = std::thread(&CpuCollector::Collect, this);
    }
  }
  
  void CpuCollector::Stop() {
    if (is_running_.exchange(false)) {
      sampler_thread_.join();
    }
  }
  
  void CpuCollector::Collect() {
    SetThreadName("Studio:PollCpu");
  
    Stopwatch stopwatch;
    while (is_running_.load()) {
      Trace::Begin("CPU:Collect");
      stopwatch.Start();
      usage_sampler_.Sample();
      thread_monitor_.Monitor();
      int64_t elapsed_time_us = Clock::ns_to_us(stopwatch.GetElapsed());
      Trace::End();
      if (sampling_interval_in_us_ > elapsed_time_us) {
        usleep(sampling_interval_in_us_ - elapsed_time_us);
      } else {
        // Do not sleep. Read data for the next round immediately.
      }
    }
  }
  
  }  // namespace profiler
  