Commit 8f485542 authored Sep 25, 2015 by Dietmar Eggemann Committed by Dmitry Shmidt Jan 31, 2017

ANDROID: arm64: Enable max freq invariant scheduler load-tracking and capacity support



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.

Including <linux/cpufreq.h> in topology.h like for the arm arch doesn't
work because of CONFIG_COMPAT=y (Kernel support for 32-bit EL0).
That's why cpufreq_scale_max_freq_capacity() has to be declared extern
in topology.h.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Andres Oportus <andresoportus@google.com>

parent 568913e2

arch/arm64/include/asm/topology.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -35,6 +35,7 @@ struct sched_domain;
		#ifdef CONFIG_CPU_FREQ
		#define arch_scale_freq_capacity cpufreq_scale_freq_capacity
		extern unsigned long cpufreq_scale_freq_capacity(struct sched_domain *sd, int cpu);
		extern unsigned long cpufreq_scale_max_freq_capacity(int cpu);
		#endif
		#define arch_scale_cpu_capacity scale_cpu_capacity
		extern unsigned long scale_cpu_capacity(struct sched_domain *sd, int cpu);

arch/arm64/kernel/topology.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -29,7 +29,13 @@ static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;

		unsigned long scale_cpu_capacity(struct sched_domain *sd, int cpu)
		{
		#ifdef 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)