Fixing a corner case in asymmetric CPU packing

Linux supports processor architectures where CPUs in the same system might have different processing capacities; for example, the Arm big.LITTLE systems combine fast, power-hungry CPUs with slower, more efficient ones. Linux has also run for years on simultaneous multithreading (SMT) architectures, where one CPU executes multiple independent execution threads and is seen as if it were multiple cores. There are architectures that mix both approaches. A recent discussion on a patch set submitted by Ricardo Neri shows that, on these systems, the scheduler might distribute tasks in an inefficient way.

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