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

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Message-ID: <20231217175923.wxmfocgckpaytptb@airbuntu>
Date: Sun, 17 Dec 2023 17:59:23 +0000
From: Qais Yousef <qyousef@...alina.io>
To: Lukasz Luba <lukasz.luba@....com>
Cc: linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	rafael@...nel.org, dietmar.eggemann@....com, rui.zhang@...el.com,
	amit.kucheria@...durent.com, amit.kachhap@...il.com,
	daniel.lezcano@...aro.org, viresh.kumar@...aro.org,
	len.brown@...el.com, pavel@....cz, mhiramat@...nel.org,
	wvw@...gle.com
Subject: Re: [PATCH v5 09/23] PM: EM: Use runtime modified EM for CPUs energy
 estimation in EAS

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@....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
>