https://qooah.com/2013/10/31/%e5%82%b3%e8%81%9e-android-4-4-%e5%b0%87%e9%87%8d%e9%bb%9e%e5%84%aa%e5%8c%96%e4%bb%a5%e9%85%8d%e5%90%88-512-mb-ram-%e6%a9%9f%e7%a8%ae/