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cpufreq: Max freq invariant scheduler load-tracking and cpu capacity support

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Implements cpufreq_scale_max_freq_capacity() to provide the scheduler
with a maximum frequency scaling correction factor for more accurate
load-tracking and cpu capacity handling by being able to deal with
frequency capping.

This scaling factor describes the influence of running a cpu with a
current maximum frequency lower than the absolute possible maximum
frequency on load tracking and cpu capacity.

The factor is:

	current_max_freq(cpu) << SCHED_CAPACITY_SHIFT / max_freq(cpu)

In fact, max_freq_scale should be a struct cpufreq_policy data member.
But this would require that the scheduler hot path (__update_load_avg())
would have to grab the cpufreq lock. This can be avoided by using per-cpu
data initialized to SCHED_CAPACITY_SCALE for max_freq_scale.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
This commit is contained in:
Dietmar Eggemann
2015-09-22 16:47:48 +01:00
committed by Leo Yan
parent 8296e78e5e
commit b03f1ba3d5
2 changed files with 20 additions and 0 deletions
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19
drivers/cpufreq/cpufreq.c
View File

@@ -352,12 +352,14 @@ static void adjust_jiffies(unsigned long val, struct cpufreq_freqs *ci)
*********************************************************************/
static DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
static DEFINE_PER_CPU(unsigned long, max_freq_scale) = SCHED_CAPACITY_SCALE;
static void
scale_freq_capacity(struct cpufreq_policy *policy, struct cpufreq_freqs *freqs)
{
unsigned long cur = freqs ? freqs->new : policy->cur;
unsigned long scale = (cur << SCHED_CAPACITY_SHIFT) / policy->max;
struct cpufreq_cpuinfo *cpuinfo = &policy->cpuinfo;
int cpu;
pr_debug("cpus %*pbl cur/cur max freq %lu/%u kHz freq scale %lu\n",
@@ -365,6 +367,18 @@ scale_freq_capacity(struct cpufreq_policy *policy, struct cpufreq_freqs *freqs)
for_each_cpu(cpu, policy->cpus)
per_cpu(freq_scale, cpu) = scale;
if (freqs)
return;
scale = (policy->max << SCHED_CAPACITY_SHIFT) / cpuinfo->max_freq;
pr_debug("cpus %*pbl cur max/max freq %u/%u kHz max freq scale %lu\n",
cpumask_pr_args(policy->cpus), policy->max, cpuinfo->max_freq,
scale);
for_each_cpu(cpu, policy->cpus)
per_cpu(max_freq_scale, cpu) = scale;
}
unsigned long cpufreq_scale_freq_capacity(struct sched_domain *sd, int cpu)
@@ -372,6 +386,11 @@ unsigned long cpufreq_scale_freq_capacity(struct sched_domain *sd, int cpu)
return per_cpu(freq_scale, cpu);
}
unsigned long cpufreq_scale_max_freq_capacity(int cpu)
{
return per_cpu(max_freq_scale, cpu);
}
static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
struct cpufreq_freqs *freqs, unsigned int state)
{

1
include/linux/cpufreq.h
View File

@@ -619,4 +619,5 @@ int cpufreq_generic_init(struct cpufreq_policy *policy,
struct sched_domain;
unsigned long cpufreq_scale_freq_capacity(struct sched_domain *sd, int cpu);
unsigned long cpufreq_scale_max_freq_capacity(int cpu);
#endif /* _LINUX_CPUFREQ_H */