linux-kernel - Re: [PATCH v1 1/3] cpufreq: CPPC: Add cppc_cpufreq_search_cpu

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Message-ID: <746641141c630dc1d02943d6133a6c8d@kernel.org>
Date:   Thu, 17 Mar 2022 14:20:42 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Pierre Gondois <Pierre.Gondois@....com>
Cc:     linux-kernel@...r.kernel.org, Ionela.Voinescu@....com,
        Lukasz.Luba@....com, Morten.Rasmussen@....com,
        Dietmar.Eggemann@....com, mka@...omium.org,
        daniel.lezcano@...aro.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Fuad Tabba <tabba@...gle.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Rob Herring <robh@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v1 1/3] cpufreq: CPPC: Add cppc_cpufreq_search_cpu_data

On 2022-03-17 13:34, Pierre Gondois wrote:
> cppc_cpufreq_get_cpu_data() allocates a new struct cppc_cpudata
> for the input CPU at each call.
> 
> To search the struct associated with a cpu without allocating
> a new one, add cppc_cpufreq_search_cpu_data().
> Also add an early prototype.
> 
> This will be used in a later patch, when generating artificial
> performance states to register an artificial Energy Model in the
> cppc_cpufreq driver and enable the Energy Aware Scheduler for ACPI
> based systems.
> 
> Signed-off-by: Pierre Gondois <Pierre.Gondois@....com>
> ---
>  drivers/cpufreq/cppc_cpufreq.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/cpufreq/cppc_cpufreq.c 
> b/drivers/cpufreq/cppc_cpufreq.c
> index 82d370ae6a4a..8f950fe72765 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -41,6 +41,8 @@
>   */
>  static LIST_HEAD(cpu_data_list);
> 
> +static struct cppc_cpudata *cppc_cpufreq_search_cpu_data(unsigned int 
> cpu);
> +
>  static bool boost_supported;
> 
>  struct cppc_workaround_oem_info {
> @@ -479,6 +481,19 @@ static void cppc_cpufreq_put_cpu_data(struct
> cpufreq_policy *policy)
>  	policy->driver_data = NULL;
>  }
> 
> +static inline struct cppc_cpudata *

Why the inline? This is hardly performance critical, and if
it is, you want something better than iterating over a list.

> +cppc_cpufreq_search_cpu_data(unsigned int cpu)
> +{
> +	struct cppc_cpudata *iter, *tmp;
> +
> +	list_for_each_entry_safe(iter, tmp, &cpu_data_list, node) {
> +		if (cpumask_test_cpu(cpu, iter->shared_cpu_map))
> +			return iter;
> +	}
> +
> +	return NULL;
> +}
> +
>  static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
>  {
>  	unsigned int cpu = policy->cpu;

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...