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arm: Enable max freq invariant scheduler load-tracking and capacity support

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Maximum Frequency Invariance has to be part of Cpu Invariance because
Frequency Invariance deals only with differences in load-tracking
introduces by Dynamic Frequency Scaling and not with limiting the
possible range of cpu frequency.

By placing Maximum Frequency Invariance into Cpu Invariance,
load-tracking is scaled via arch_scale_cpu_capacity()
in __update_load_avg() and cpu capacity is scaled via
arch_scale_cpu_capacity() in update_cpu_capacity().

To be able to save the extra multiplication in the scheduler hotpath
(__update_load_avg()) we could:

 1 Inform cpufreq about base cpu capacity at boot and let it handle
   scale_cpu_capacity() as well.
 2 Use the cpufreq policy callback which would update a per-cpu current
   cpu_scale and this value would be return in scale_cpu_capacity().
 3 Use per-cpu current max_freq_scale and current cpu_scale with the
   current patch.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
This commit is contained in:
Dietmar Eggemann
2015-09-23 17:59:55 +01:00
committed by Leo Yan
parent 05a773bfc9
commit 5414a72fc3
1 changed files with 6 additions and 0 deletions
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6
arch/arm/kernel/topology.c
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@@ -44,7 +44,13 @@ static DEFINE_PER_CPU(unsigned long, cpu_scale);
unsigned long scale_cpu_capacity(struct sched_domain *sd, int cpu)
{
#if CONFIG_CPU_FREQ
unsigned long max_freq_scale = cpufreq_scale_max_freq_capacity(cpu);
return per_cpu(cpu_scale, cpu) * max_freq_scale >> SCHED_CAPACITY_SHIFT;
#else
return per_cpu(cpu_scale, cpu);
#endif
}
static void set_capacity_scale(unsigned int cpu, unsigned long capacity)