On Wed, 25 Oct 2023 at 22:13, Dietmar Eggemann [off-list ref] wrote:

On 18/10/2023 18:25, Vincent Guittot wrote:

quoted

cpuinfo.max_freq can change at runtime because of boost as an example. This
implies that the value could be different than the one that has been
used when computing the capacity of a CPU.

The new arch_scale_freq_ref() returns a fixed and coherent reference
frequency that can be used when computing a frequency based on utilization.

Use this arch_scale_freq_ref() when available and fallback to
policy otherwise.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>

---
 kernel/sched/cpufreq_schedutil.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 458d359f5991..6e4030482ae8 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c

@@ -114,6 +114,28 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy)
      }
 }

+/**
+ * cpufreq_get_capacity_ref_freq - get the reference frequency of a given CPU that

s/cpufreq_get_capacity_ref_freq/get_capacity_ref_freq

s/of a given CPU/for a given cpufreq policy ? (of which the CPU managing
it is used for the arch_scale_freq_ref() call in the function.

quoted

+ * has been used to correlate frequency and compute capacity.
+ * @policy: the cpufreq policy of the CPU in question.
+ * @use_current: Fallback to current freq instead of policy->cpuinfo.max_freq.

Looks like use_current does not exists as a parameter.

Thanks for the review. I'm going to apply your comments

quoted

+ *
+ * Return: the reference CPU frequency to compute a capacity.
+ */
+static __always_inline
+unsigned long get_capacity_ref_freq(struct cpufreq_policy *policy)
+{
+     unsigned int freq = arch_scale_freq_ref(policy->cpu);
+
+     if (freq)
+             return freq;
+
+     if (arch_scale_freq_invariant())
+             return policy->cpuinfo.max_freq;
+
+     return policy->cur;
+}

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

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