[PATCH v1 2/2] cpufreq: update capacity_freq_ref when the boost state changes
Oleg Keri
okerixx at gmail.com
Sun Sep 6 09:37:15 PDT 2026
capacity_freq_ref is latched from policy->cpuinfo.max_freq by
init_cpu_capacity_callback() on CPUFREQ_CREATE_POLICY, and never
updated afterwards.
cpufreq_frequency_table_cpuinfo() excludes CPUFREQ_BOOST_FREQ entries
while boost is disabled, so on a system that boots with boost off the
latched value is the non-boost maximum. Enabling boost later raises
policy->cpuinfo.max_freq but leaves capacity_freq_ref behind.
Two things then go wrong on arm64, where the AMU drives frequency
invariance. amu_scale_freq_tick() caps the computed scale at
SCHED_CAPACITY_SCALE, so a CPU running above capacity_freq_ref
saturates at 1024: the scheduler cannot tell a boosted CPU from one at
the sustained maximum, and utilisation is underestimated. And
arch_freq_get_on_cpu(), which reverses that computation, cannot report
more than capacity_freq_ref, so cpuinfo_avg_freq is pinned to the
non-boost maximum.
On a Snapdragon X2 Elite (Glymur) laptop with a 4032000 kHz sustained
and a 4723200 kHz boost OPP, cpuinfo_avg_freq reads exactly 4032000
while the CPU runs at 4723200; a fixed workload completes in 1.72 s
rather than the 2.01 s that frequency would imply.
Factor the update out of init_cpu_capacity_callback() into
topology_update_freq_ref() and call it from policy_set_boost(), which
is the common path for the global boost knob, the per-policy one, and
the CPU online path.
Signed-off-by: Oleg Keri <okerixx at gmail.com>
---
arch/arm/include/asm/topology.h | 1 +
arch/arm64/include/asm/topology.h | 1 +
arch/riscv/include/asm/topology.h | 1 +
drivers/base/arch_topology.c | 19 +++++++++++++------
drivers/cpufreq/cpufreq.c | 2 ++
include/linux/arch_topology.h | 1 +
include/linux/cpufreq.h | 7 +++++++
7 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
index ad36b6570067..a776a79885ee 100644
--- a/arch/arm/include/asm/topology.h
+++ b/arch/arm/include/asm/topology.h
@@ -11,6 +11,7 @@
#ifndef CONFIG_BL_SWITCHER
/* Replace task scheduler's default frequency-invariant accounting */
#define arch_set_freq_scale topology_set_freq_scale
+#define arch_update_freq_ref topology_update_freq_ref
#define arch_scale_freq_capacity topology_get_freq_scale
#define arch_scale_freq_invariant topology_scale_freq_invariant
#define arch_scale_freq_ref topology_get_freq_ref
diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
index b9eaf4ad7085..a4b96a7ee4a5 100644
--- a/arch/arm64/include/asm/topology.h
+++ b/arch/arm64/include/asm/topology.h
@@ -22,6 +22,7 @@ void update_freq_counters_refs(void);
/* Replace task scheduler's default frequency-invariant accounting */
#define arch_scale_freq_tick topology_scale_freq_tick
#define arch_set_freq_scale topology_set_freq_scale
+#define arch_update_freq_ref topology_update_freq_ref
#define arch_scale_freq_capacity topology_get_freq_scale
#define arch_scale_freq_invariant topology_scale_freq_invariant
#define arch_scale_freq_ref topology_get_freq_ref
diff --git a/arch/riscv/include/asm/topology.h b/arch/riscv/include/asm/topology.h
index fe1a8bf6902d..a363d72c174f 100644
--- a/arch/riscv/include/asm/topology.h
+++ b/arch/riscv/include/asm/topology.h
@@ -11,6 +11,7 @@
/* Replace task scheduler's default frequency-invariant accounting */
#define arch_scale_freq_tick topology_scale_freq_tick
#define arch_set_freq_scale topology_set_freq_scale
+#define arch_update_freq_ref topology_update_freq_ref
#define arch_scale_freq_capacity topology_get_freq_scale
#define arch_scale_freq_invariant topology_scale_freq_invariant
#define arch_scale_freq_ref topology_get_freq_ref
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 8c5e47c28d9a..79eb1681065d 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -317,6 +317,18 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
return !ret;
}
+void topology_update_freq_ref(const struct cpumask *cpus, unsigned int max_freq)
+{
+ int cpu;
+
+ for_each_cpu(cpu, cpus) {
+ per_cpu(capacity_freq_ref, cpu) = max_freq;
+ freq_inv_set_max_ratio(cpu,
+ per_cpu(capacity_freq_ref, cpu) * HZ_PER_KHZ);
+ }
+}
+EXPORT_SYMBOL_GPL(topology_update_freq_ref);
+
void __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
{
}
@@ -392,7 +404,6 @@ init_cpu_capacity_callback(struct notifier_block *nb,
void *data)
{
struct cpufreq_policy *policy = data;
- int cpu;
if (val != CPUFREQ_CREATE_POLICY)
return 0;
@@ -403,11 +414,7 @@ init_cpu_capacity_callback(struct notifier_block *nb,
cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus);
- for_each_cpu(cpu, policy->related_cpus) {
- per_cpu(capacity_freq_ref, cpu) = policy->cpuinfo.max_freq;
- freq_inv_set_max_ratio(cpu,
- per_cpu(capacity_freq_ref, cpu) * HZ_PER_KHZ);
- }
+ topology_update_freq_ref(policy->related_cpus, policy->cpuinfo.max_freq);
if (cpumask_empty(cpus_to_visit)) {
if (raw_capacity) {
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 0d0df986fa3d..289649baa061 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -594,6 +594,8 @@ static int policy_set_boost(struct cpufreq_policy *policy, bool enable)
return ret;
}
+ arch_update_freq_ref(policy->related_cpus, policy->cpuinfo.max_freq);
+
return 0;
}
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index ebd7f8935f96..4974f5e1a7fe 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -31,6 +31,7 @@ static inline unsigned long topology_get_freq_scale(int cpu)
void topology_set_freq_scale(const struct cpumask *cpus, unsigned long cur_freq,
unsigned long max_freq);
+void topology_update_freq_ref(const struct cpumask *cpus, unsigned int max_freq);
bool topology_scale_freq_invariant(void);
enum scale_freq_source {
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 35ce665edfd8..5b904e13eb21 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -1235,6 +1235,13 @@ void arch_set_freq_scale(const struct cpumask *cpus,
}
#endif
+#ifndef arch_update_freq_ref
+static __always_inline
+void arch_update_freq_ref(const struct cpumask *cpus, unsigned int max_freq)
+{
+}
+#endif
+
/* the following are really really optional */
extern struct freq_attr cpufreq_freq_attr_scaling_available_freqs;
extern struct freq_attr cpufreq_freq_attr_scaling_boost_freqs;
--
2.55.0
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