Why are light apps using 8 cores?
If you look at an app like Gmail you will notice and interesting phenomenon. On a quad-core phone the core usage was evenly split between 2 and 4 cores, but on an octa-core phone the app used between 4 and 8 cores. How come Gmail can run on 2 to 4 cores on a quad-core phone but needs at least four cores on an octa-core phone? That doesn’t make sense!
The key again is to remember that on big.LITTLE phones not all the cores are equal. What we are actually seeing is how the scheduler is using the LITTLE cores then as the workload increases the big core are brought into play. For a while there is a small amount of crossover and then the LITTLE cores go to sleep. Then when the workload decreases the opposite happens. Of course this is all happening very fast, thousands of times per second. Look at this graph which shows the utilization of big vs LITTLE cores during my testing of Epic Citadel: