Re: [PATCH v5 09/23] PM: EM: Use runtime modified EM for CPUs energy estimation in EAS

Qais Yousef
2023-12-17T17:59:26Z

On 11/29/23 11:08, Lukasz Luba wrote:
> The new Energy Model (EM) supports runtime modification of the performance
> state table to better model the power used by the SoC. Use this new
> feature to improve energy estimation and therefore task placement in
> Energy Aware Scheduler (EAS).

nit: you moved the code to use the new runtime em table instead of the one
parsed at boot.

>
> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
> ---
> include/linux/energy_model.h | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
> index 1e618e431cac..94a77a813724 100644
> --- a/include/linux/energy_model.h
> +++ b/include/linux/energy_model.h
> @@ -238,6 +238,7 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
> unsigned long max_util, unsigned long sum_util,
> unsigned long allowed_cpu_cap)
> {
> + struct em_perf_table *runtime_table;
> unsigned long freq, scale_cpu;
> struct em_perf_state *ps;
> int cpu, i;
> @@ -255,7 +256,14 @@ 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];
> +
> + /*
> + * No rcu_read_lock() since it's already called by task scheduler.
> + * The runtime_table is always there for CPUs, so we don't check.
> + */

WARN_ON(rcu_read_lock_held()) instead?

Cheers

--
Qais Yousef

> + runtime_table = rcu_dereference(pd->runtime_table);
> +
> + ps = &runtime_table->state[pd->nr_perf_states - 1];
>
> max_util = map_util_perf(max_util);
> max_util = min(max_util, allowed_cpu_cap);
> @@ -265,9 +273,9 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
> * Find the lowest performance state of the Energy Model above the
> * requested frequency.
> */
> - i = em_pd_get_efficient_state(pd->table, pd->nr_perf_states, freq,
> - pd->flags);
> - ps = &pd->table[i];
> + i = em_pd_get_efficient_state(runtime_table->state, pd->nr_perf_states,
> + freq, pd->flags);
> + ps = &runtime_table->state[i];
>
> /*
> * The capacity of a CPU in the domain at the performance state (ps)
> --
> 2.25.1
>