https://blog.toright.com/posts/12/%e5%9c%a8-linux-%e5%8f%96%e5%be%97%e7%b3%bb%e7%b5%b1-cpu-%e8%b3%87%e8%a8%8a%e8%88%87-cpu-%e4%bd%8d%e5%85%83%e8%b3%87%e8%a8%8a