Dietmar Eggemann authored Nov 14, 2014 and Morten Rasmussen committed Feb 02, 2015

Apply frequency scale-invariance correction factor to load tracking.
Each segment of the sched_avg::runnable_avg_sum geometric series is now
scaled by the current frequency so the sched_avg::load_avg_contrib of each
entity will be invariant with frequency scaling. As a result,
cfs_rq::runnable_load_avg which is the sum of sched_avg::load_avg_contrib,
becomes invariant too. So the load level that is returned by
weighted_cpuload, stays relative to the max frequency of the cpu.

Then, we want the keep the load tracking values in a 32bits type, which
implies that the max value of sched_avg::{runnable|running}_avg_sum must
be lower than 2^32/88761=48388 (88761 is the max weight of a task). As
LOAD_AVG_MAX = 47742, arch_scale_freq_capacity must return a value less
than (48388/47742) << SCHED_CAPACITY_SHIFT = 1037 (SCHED_SCALE_CAPACITY =
1024). So we define the range to [0..SCHED_SCALE_CAPACITY] in order to
avoid overflow.

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