How to get the Android L performance boost on your phone now (swap Dalvik with ART tutorial)
The tutorial below will work with Android 4.4 KitKat (and newer) devices - earlier ones simply did not have that option. Luckily, this includes not just the Google Nexus series, but also popular phones like the Samsung Galaxy S5, HTC One (M8), the LG G3, and so on.
How to do it? First, go into Settings, scroll to the bottom, and tap on "About phone." There, you'd see the "Build number" field - tap on it seven consecutive times, and this will enable 'Developer options'. The second step is to now go back to the Settings menu and find the newly-appeared 'Developer options' menu where you should look for 'Select runtime'.