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drivers base/arch_topology: provide frequency-invariant accounting support 

Implements the arch-specific (arm and arm64) frequency-invariance setter
function arch_set_freq_scale() which provides the following frequency
scaling factor:

  current_freq(cpu) << SCHED_CAPACITY_SHIFT / max_supported_freq(cpu)

One possible consumer of the frequency-invariance getter function
topology_get_freq_scale() is the Per-Entity Load Tracking (PELT)
mechanism of the task scheduler.

Allow inlining of topology_get_freq_scale() into the task scheduler
fast path (e.g. __update_load_avg_se()) by coding it as a static inline
function in the arch topology header file.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Dietmar Eggemann 2017-09-26 17:41:10 +01:00 committed by Rafael J. Wysocki
parent 400ec74d3b
commit 0e27c567d1
2 changed files with 23 additions and 0 deletions
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14
drivers/base/arch_topology.c
View File

@ -22,6 +22,20 @@
#include <linux/string.h>
#include <linux/sched/topology.h>
DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
unsigned long max_freq)
{
unsigned long scale;
int i;
scale = (cur_freq << SCHED_CAPACITY_SHIFT) / max_freq;
for_each_cpu(i, cpus)
per_cpu(freq_scale, i) = scale;
}
static DEFINE_MUTEX(cpu_scale_mutex);
static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;

9
include/linux/arch_topology.h
View File

@ -5,6 +5,7 @@
#define _LINUX_ARCH_TOPOLOGY_H_
#include <linux/types.h>
#include <linux/percpu.h>
void topology_normalize_cpu_scale(void);
@ -16,4 +17,12 @@ unsigned long topology_get_cpu_scale(struct sched_domain *sd, int cpu);
void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity);
DECLARE_PER_CPU(unsigned long, freq_scale);
static inline
unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu)
{
return per_cpu(freq_scale, cpu);
}
#endif /* _LINUX_ARCH_TOPOLOGY_H_ */