mac OS get cpu usage by pid

• (float)getCpuUsage:(unsigned int)pid
  {
  kern_return_t kr;
  thread_array_t thread_list;
  mach_msg_type_number_t thread_count;
  thread_info_data_t thinfo;
  mach_msg_type_number_t thread_info_count;
  thread_basic_info_t basic_info_th;

  mach_port_name_t task;
  int error = task_for_pid(mach_task_self(), pid, &task);
  if (error)
  {
  printf(“task_for_pid return error:\n %s\n”, mach_error_string(error));
  } else {
  printf(“Get the process %d’s task port : %x\n”, pid, task);
  }

  kr = task_threads(task, &thread_list, &thread_count);
  if (kr != KERN_SUCCESS) {
  return -1;
  }
  float cpu_usage = 0;

  for (int i = 0; i < thread_count; i++)
  {
  thread_info_count = THREAD_INFO_MAX;
  kr = thread_info(thread_list[i], THREAD_BASIC_INFO,(thread_info_t)thinfo, &thread_info_count);
  if (kr != KERN_SUCCESS) {
  return -1;
  }

    basic_info_th = (thread_basic_info_t)thinfo;
    
    if (!(basic_info_th->flags & TH_FLAGS_IDLE))
    {
        cpu_usage += basic_info_th->cpu_usage;
    }
  

  }
  cpu_usage = cpu_usage / (float)TH_USAGE_SCALE * 100.0;

  vm_deallocate((mach_port_t)pid, (vm_offset_t)thread_list, thread_count * sizeof(thread_t));

  return cpu_usage;
  }

获取子进程的CPU使用率需要在子进程中运行上面程序，然后通过IPC获得