ANDROID: cpufreq: Frequency invariant scheduler load-tracking support
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>
Signed-off-by: Andres Oportus <andresoportus@google.com>
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index c910111..6f2dae7 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -301,6 +301,31 @@
#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)
{
@@ -405,6 +430,8 @@
spin_unlock(&policy->transition_lock);
+ scale_freq_capacity(policy, freqs);
+
cpufreq_notify_transition(policy, freqs, CPUFREQ_PRECHANGE);
}
EXPORT_SYMBOL_GPL(cpufreq_freq_transition_begin);
@@ -2192,6 +2219,8 @@
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;
trace_cpu_frequency_limits(policy->max, policy->min, policy->cpu);