Note:
This tutorial is already outdated, from improve performance and battery life to https adaway org. It barely increases your battery life and doesn't yield any extra performance while you have to install so much stuff and configure complex stuff
Here's the new, simple tweak to replace all that, same battery life, but MUCH better performance:
For maximum performance (Battery life will not be affected):
Ktweak (download from play store, needs root), select throughput for highest performance
Smartpack (download from play store, needs root) - Set CPU minimums and maximums to the highest value possible.
Go to GPU section, and then set GPU min freq and max freq to the highest value
Go to I/O section, and then click disable I/O stats.
NOTE: APPLY ON BOOT MUST BE ENABLED ON BOTH KTWEAK AND SMARTPACK !!! (FOR SMARTPACK, APPLY ON BOOT OPTION IS IN SETTINGS AND THEN SELECT 15 SECONDS FOR THE DELAY AND THEN GO TO CPU GPU AND THEN I/O AND TAP ON APPLY ON BOOT)