From 25fd93de74994e4bdcec2ec4ed0814207a8e0e4b Mon Sep 17 00:00:00 2001
From: Dietmar Eggemann <dietmar.eggemann@arm.com>
Date: Tue, 22 Sep 2015 16:47:48 +0100
Subject: [PATCH] cpufreq: Max freq invariant scheduler load-tracking and cpu
capacity support
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>
---
drivers/cpufreq/cpufreq.c | 19 +++++++++++++++++++
include/linux/cpufreq.h | 1 +
2 files changed, 20 insertions(+)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 46a7d62c8174..96f1a8860819 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -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)
{
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 11c65f536b6c..9b1d61e1f1d7 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -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 */
--
2.34.1