Tweaking CPU settings can be a very safe and easy way for rooted Android users to save a bit of that precious battery juice. More often than not, this can only be achieved by downloading a third party app, as only very few OEMs offer CPU speed controls in their built-in software. But if you own a Sony Xperia device and are up for a bit of coding, check out XDA Senior Member Pandemic’s tutorial on adding CPU settings into the native settings menu.
The process explained in the tutorial is very straightforward with not many complexities, perfect for the beginner looking to dip his or her toes in the pool but not yet ready to dive into the deep end of Android development. After downloading the attached files from the guide, you need decompile the settings.apk, navigate to the specified XML files which you then must add a few lines of code to, and recompile it. Once this is done, all you have to do is either make a flashable zip folder with the two APKs provided and the edited settings.apk and flash it through a custom recovery, or simply push these files manually to the system folder.
When you’re done, you’ll end up with a settings menu that has a new sub menu that enables you to change the CPU clock speeds, as well as view statistics regarding your device’s CPU such as the total run time and how long your CPU spends running at certain clock speeds.
If you would like to give this a whirl, visit the original thread for more information.