code: function getCpuUsage(previousValue, start) {
    if (!previousValue) {
      return null;
    }
    const usage = process.cpuUsage(previousValue);
    const delta = process.hrtime(start);
    const total = Math.ceil(((delta[0] * 1e9) + delta[1]) / 1000);
    const usedPercent = Math.round(((usage.user + usage.system) / total) * 100);
    usage.usedPercent = usedPercent;
    usage.userUsedPercent = Math.round((usage.user / total) * 100);
    usage.systemUsedPercent = Math.round((usage.system / total) * 100);
    usage.total = total;
    return usage;
  }
docs: Get the cpu usage
  @param {Object} previousValue The previous cpu usage
  @param {Array} start The previous process.hrtime
  @returns {Object} The cpu usage {
  user: Number,
  system: Number,
  usedPercent: Number,
  userUsedPercent: Number,
  systemUsedPercent: Number,
  total: total
  }