如何改进react 16.4中数组状态的慢更新

我使用的是react 16.4,我有一个setState,它占用了将近800毫秒,我不知道为什么。

      let shown_wbs = [...this.state.shown_wbs];
      console.log(shown_wbs);

      // and reset the line item value
      console.log("before set");
      let current = new Date().getTime();
      let difference = current - last_known;
      console.log(difference);
      last_known = current;
      shown_wbs.push("somestring");
      console.log("set state");
      current = new Date().getTime();
      difference = current - last_known;
      console.log(difference);
      last_known = current;
      this.setState({
        shown_wbs: shown_wbs,
      });
      console.log("after set state");
      current = new Date().getTime();
      difference = current - last_known;
      console.log(difference);
      last_known = current;

本例中的数组只是一个字符串数组。

如何提高设置状态的速度?