On Mon, 23 Oct 2023 at 22:58, Ionela Voinescu [off-list ref] wrote:

Hi,

On Wednesday 18 Oct 2023 at 18:25:40 (+0200), Vincent Guittot wrote:

quoted

Use the new capacity_ref_freq to set the ratio that is used by AMU for
computing the arch_scale_freq_capacity().
This helps to keep everything aligned using the same reference for
computing CPUs capacity.

The default value of the ratio ensures that arch_scale_freq_capacity()
returns max capacity until it is set to its correct value with the
cpu capacity and capacity_ref_freq.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
 arch/arm64/kernel/topology.c  | 18 ++++++++++--------
 drivers/base/arch_topology.c  | 14 ++++++++++++--
 include/linux/arch_topology.h |  1 +
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 817d788cd866..0f8f6e90c46d 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c

@@ -82,7 +82,12 @@ int __init parse_acpi_topology(void)
 #undef pr_fmt
 #define pr_fmt(fmt) "AMU: " fmt

-static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale);
+/*
+ * Ensure that amu_scale_freq_tick() will return SCHED_CAPACITY_SHIFT until
+ * the CPU capacity and its assosciated frequency have been correctly
+ * initialized.

s/SCHED_CAPACITY_SHIFT/SCHED_CAPACITY_SCALE

quoted

+ */
+static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = (2 * SCHED_CAPACITY_SHIFT);

It should be 1UL << (2 * SCHED_CAPACITY_SHIFT).

yes

quoted

 static DEFINE_PER_CPU(u64, arch_const_cycles_prev);
 static DEFINE_PER_CPU(u64, arch_core_cycles_prev);
 static cpumask_var_t amu_fie_cpus;

@@ -112,9 +117,9 @@ static inline bool freq_counters_valid(int cpu)
      return true;
 }

-static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
+int freq_inv_set_max_ratio(int cpu, u64 max_rate)
 {
-     u64 ratio;
+     u64 ratio, ref_rate = arch_timer_get_rate();

      if (unlikely(!max_rate || !ref_rate)) {
              pr_debug("CPU%d: invalid maximum or reference frequency.\n",

@@ -142,7 +147,7 @@ static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
              return -EINVAL;
      }

The return value is no longer used so it might be worth declaring it to
return void and WARN_ONCE for unlikely(!max_rate || !ref_rate).

quoted

-     per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
+     WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);

      return 0;
 }

@@ -195,10 +200,7 @@ static void amu_fie_setup(const struct cpumask *cpus)
              return;

      for_each_cpu(cpu, cpus) {
-             if (!freq_counters_valid(cpu) ||
-                 freq_inv_set_max_ratio(cpu,
-                                        cpufreq_get_hw_max_freq(cpu) * 1000ULL,
-                                        arch_timer_get_rate()))
+             if (!freq_counters_valid(cpu))
                      return;
      }

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 2372ce791bb4..3a604b77b12d 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c

@@ -344,6 +344,11 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
      return !ret;
 }

+int __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
+{
+     return 0;
+}
+
 #ifdef CONFIG_ACPI_CPPC_LIB
 #include <acpi/cppc_acpi.h>

@@ -369,7 +374,6 @@ void topology_init_cpu_capacity_cppc(void)
                      capacity_scale = max_t(u64, capacity_scale, raw_capacity[cpu]);

                      per_cpu(capacity_ref_freq, cpu) = cppc_perf_to_khz(&perf_caps, raw_capacity[cpu]);
-
                      pr_debug("cpu_capacity: CPU%d cpu_capacity=%u (raw).\n",
                               cpu, raw_capacity[cpu]);
                      continue;

@@ -381,6 +385,9 @@ void topology_init_cpu_capacity_cppc(void)
      }

      for_each_possible_cpu(cpu) {
+             freq_inv_set_max_ratio(cpu,
+                                    per_cpu(capacity_ref_freq, cpu));
+
              capacity = raw_capacity[cpu];
              capacity = div64_u64(capacity << SCHED_CAPACITY_SHIFT,
                                   capacity_scale);

@@ -422,8 +429,11 @@ 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)
+     for_each_cpu(cpu, policy->related_cpus) {
              per_cpu(capacity_ref_freq, cpu) = policy->cpuinfo.max_freq;
+             freq_inv_set_max_ratio(cpu,
+                                    per_cpu(capacity_ref_freq, cpu));

capacity_ref_freq is in KHz while arch_timer_get_rate() is in Hz. One or
the other needs to be scaled.

The same in topology_init_cpu_capacity_cppc().

Thanks,
Ionela.

quoted

+     }

      if (cpumask_empty(cpus_to_visit)) {
              topology_normalize_cpu_scale();

diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 38ca6c76af56..b6e95d763279 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h

@@ -99,6 +99,7 @@ void update_siblings_masks(unsigned int cpu);
 void remove_cpu_topology(unsigned int cpuid);
 void reset_cpu_topology(void);
 int parse_acpi_topology(void);
+int freq_inv_set_max_ratio(int cpu, u64 max_rate);
 #endif

 #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
--

2.34.1

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