[PATCH v4 1/5] cpufreq: Add a cpufreq pressure feedback for the scheduler

Vincent Guittot
2024-01-09T16:47:02Z

Provide to the scheduler a feedback about the temporary max available
capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
filtered as the pressure will happen for dozens ms or more.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
drivers/cpufreq/cpufreq.c | 36 ++++++++++++++++++++++++++++++++++++
include/linux/cpufreq.h | 10 ++++++++++
2 files changed, 46 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 44db4f59c4cc..f4eee3d107f1 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2563,6 +2563,40 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
}
EXPORT_SYMBOL(cpufreq_get_policy);

+DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
+
+/**
+ * cpufreq_update_pressure() - Update cpufreq pressure for CPUs
+ * @policy: cpufreq policy of the CPUs.
+ *
+ * Update the value of cpufreq pressure for all @cpus in the policy.
+ */
+static void cpufreq_update_pressure(struct cpufreq_policy *policy)
+{
+ unsigned long max_capacity, capped_freq, pressure;
+ u32 max_freq;
+ int cpu;
+
+ cpu = cpumask_first(policy->related_cpus);
+ max_freq = arch_scale_freq_ref(cpu);
+ capped_freq = policy->max;
+
+ /*
+ * Handle properly the boost frequencies, which should simply clean
+ * the cpufreq pressure value.
+ */
+ if (max_freq <= capped_freq) {
+ pressure = 0;
+ } else {
+ max_capacity = arch_scale_cpu_capacity(cpu);
+ pressure = max_capacity -
+ mult_frac(max_capacity, capped_freq, max_freq);
+ }
+
+ for_each_cpu(cpu, policy->related_cpus)
+ WRITE_ONCE(per_cpu(cpufreq_pressure, cpu), pressure);
+}
+
/**
* cpufreq_set_policy - Modify cpufreq policy parameters.
* @policy: Policy object to modify.
@@ -2618,6 +2652,8 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
trace_cpu_frequency_limits(policy);

+ cpufreq_update_pressure(policy);
+
policy->cached_target_freq = UINT_MAX;

pr_debug("new min and max freqs are %u - %u kHz\n",
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index afda5f24d3dd..b1d97edd3253 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -241,6 +241,12 @@ struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);
void cpufreq_enable_fast_switch(struct cpufreq_policy *policy);
void cpufreq_disable_fast_switch(struct cpufreq_policy *policy);
bool has_target_index(void);
+
+DECLARE_PER_CPU(unsigned long, cpufreq_pressure);
+static inline unsigned long cpufreq_get_pressure(int cpu)
+{
+ return per_cpu(cpufreq_pressure, cpu);
+}
#else
static inline unsigned int cpufreq_get(unsigned int cpu)
{
@@ -263,6 +269,10 @@ static inline bool cpufreq_supports_freq_invariance(void)
return false;
}
static inline void disable_cpufreq(void) { }
+static inline unsigned long cpufreq_get_pressure(int cpu)
+{
+ return 0;
+}
#endif

#ifdef CONFIG_CPU_FREQ_STAT
--
2.34.1