Dietmar Eggemann authored Jan 30, 2015 and Morten Rasmussen committed Feb 02, 2015

Besides the existing frequency scale-invariance correction factor, apply
cpu scale-invariance correction factor to usage tracking.

Cpu scale-invariance takes cpu performance deviations due to
micro-architectural differences (i.e. instructions per seconds) between
cpus in HMP systems (e.g. big.LITTLE) and differences in the frequency
value of the highest OPP between cpus in SMP systems into consideration.

Each segment of the sched_avg::running_avg_sum geometric series is now
scaled by the cpu performance factor too so the
sched_avg::utilization_avg_contrib of each entity will be invariant from
the particular cpu of the HMP/SMP system it is gathered on.

So the usage level that is returned by get_cpu_usage stays relative to
the max cpu performance of the system.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>