On Thu, 14 Sept 2023 at 23:07, Dietmar Eggemann
[off-list ref] wrote:

On 01/09/2023 15:03, Vincent Guittot wrote:

[...]

quoted

diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index b9caa01dfac4..7ee07be6928e 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h

@@ -204,6 +204,20 @@ struct em_perf_state *em_pd_get_efficient_state(struct em_perf_domain *pd,
      return ps;
 }

+#ifdef arch_scale_freq_ref
+static __always_inline
+unsigned long  arch_scale_freq_ref_em(int cpu, struct em_perf_domain *pd)

Why is this function named with the arch prefix?

So far we have 5 arch functions (arch_scale_freq_tick() <->
arch_scale_freq_ref()) and e.g. Arm/Arm64 defines them with there
topology_foo implementations.

Isn't arch_scale_freq_ref_em() (as well as arch_scale_freq_ref_policy())
different in this sense and so a proper EM function which should
manifest in its name?

arch_scale_freq_ref_em() is there to handle cases where
arch_scale_freq_ref() is not defined by arch. I keep arch_ prefix
because this should be provided by architecture which wants to use EM.

In the case of EM, it's only there for allyes|randconfig on arch that
doesn't use arch_topology.c like x86_64

quoted

+{
+     return arch_scale_freq_ref(cpu);
+}
+#else
+static __always_inline
+unsigned long  arch_scale_freq_ref_em(int cpu, struct em_perf_domain *pd)
+{
+     return pd->table[pd->nr_perf_states - 1].frequency;
+}
+#endif

[...]

quoted

@@ -241,11 +255,11 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
       */
      cpu = cpumask_first(to_cpumask(pd->cpus));
      scale_cpu = arch_scale_cpu_capacity(cpu);
-     ps = &pd->table[pd->nr_perf_states - 1];
+     ref_freq = arch_scale_freq_ref_em(cpu, pd);

Why not using existing `unsigned long freq` here like in schedutil's
get_next_freq()?

Find it easier to read and understand and will not make any difference
in the compiled code

quoted

      max_util = map_util_perf(max_util);

[...]

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