Notice how at first the big cores are being used and the LITTLE cores are inactive. Then, at around the 12 second mark, the big cores start to be used less and the LITTLE cores spring to life. At the 20 second mark the big cores increase their activity again and the LITTLE cores go back down to almost zero usage. You can see this again at the 30 second mark, the 45 second mark, and at the 52 second mark.
At these points the number of cores being used fluctuates. For example, in the first 10 seconds only 3 or 4 cores are being used (big cores), and then at the 12 second mark the core usage peaks at 6 and then drops again to 4, and so on.
This is big.LITTLE in action. A big.LITTLE processor isn’t designed like the octa-core processors for PCs. The extra cores allows the scheduler to pick the right core for the right job. In all my tests I did not see any real-world apps that used all 8 cores at 100%, and that is how it should be.