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cpufreq: Frequency invariant scheduler load-tracking support

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Implements cpufreq_scale_freq_capacity() to provide the scheduler with a
frequency scaling correction factor for more accurate load-tracking.

The factor is:

	current_freq(cpu) << SCHED_CAPACITY_SHIFT / max_freq(cpu)

In fact, 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 freq_scale.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
This commit is contained in:
Dietmar Eggemann
2015-09-17 16:10:56 +01:00
committed by Leo Yan
parent 0ecbd590a7
commit 259bd4cd8a
2 changed files with 32 additions and 0 deletions
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29
drivers/cpufreq/cpufreq.c
View File

@@ -347,6 +347,31 @@ static void adjust_jiffies(unsigned long val, struct cpufreq_freqs *ci)
#endif
}
/*********************************************************************
* FREQUENCY INVARIANT CPU CAPACITY *
*********************************************************************/
static DEFINE_PER_CPU(unsigned long, 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;
int cpu;
pr_debug("cpus %*pbl cur/cur max freq %lu/%u kHz freq scale %lu\n",
cpumask_pr_args(policy->cpus), cur, policy->max, scale);
for_each_cpu(cpu, policy->cpus)
per_cpu(freq_scale, cpu) = scale;
}
unsigned long cpufreq_scale_freq_capacity(struct sched_domain *sd, int cpu)
{
return per_cpu(freq_scale, cpu);
}
static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
struct cpufreq_freqs *freqs, unsigned int state)
{
@@ -450,6 +475,8 @@ wait:
spin_unlock(&policy->transition_lock);
scale_freq_capacity(policy, freqs);
cpufreq_notify_transition(policy, freqs, CPUFREQ_PRECHANGE);
}
EXPORT_SYMBOL_GPL(cpufreq_freq_transition_begin);
@@ -2126,6 +2153,8 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
CPUFREQ_NOTIFY, new_policy);
scale_freq_capacity(new_policy, NULL);
policy->min = new_policy->min;
policy->max = new_policy->max;

3
include/linux/cpufreq.h
View File

@@ -616,4 +616,7 @@ unsigned int cpufreq_generic_get(unsigned int cpu);
int cpufreq_generic_init(struct cpufreq_policy *policy,
struct cpufreq_frequency_table *table,
unsigned int transition_latency);
struct sched_domain;
unsigned long cpufreq_scale_freq_capacity(struct sched_domain *sd, int cpu);
#endif /* _LINUX_CPUFREQ_H */