Dietmar Eggemann posted a patch from Quentin Perret to take advantage of energy-efficient CPUs on asymmetric multiprocessor (AMP) systems. AMP is distinguished from SMP (symmetric multiprocessor) systems in that an SMP system uses several instances of only one type of CPU, while an AMP system might use CPUs of differing speeds, feature-sets and so on.
Quentin's patch was an effort to take advantage of differences in power consumption between the CPUs on an AMP system. It attempted to identify the most efficient CPU that was not already saturated with processes and assign newly awakened processes to it. If no CPUs fit the bill, standard SMP-type methods of processor assignment would be used instead.