linux-kernel - Re: [RFT][PATCH v1 7/8] cpufreq: intel_pstate: Align perf domains with L2 cache

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Message-ID: <b8832097-71bd-4e68-918a-1e986457d03b@arm.com>
Date: Thu, 17 Apr 2025 13:42:10 +0100
From: Christian Loehle <christian.loehle@....com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>,
 Peter Zijlstra <peterz@...radead.org>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Morten Rasmussen <morten.rasmussen@....com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
 Pierre Gondois <pierre.gondois@....com>,
 Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [RFT][PATCH v1 7/8] cpufreq: intel_pstate: Align perf domains
 with L2 cache

On 4/16/25 19:10, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> On some hybrid platforms a group of cores (referred to as a module) may
> share an L2 cache in which case they also share a voltage regulator and
> always run at the same frequency (while not in idle states).
> 
> For this reason, make hybrid_register_perf_domain() in the intel_pstate
> driver add all CPUs sharing an L2 cache to the same perf domain for EAS.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> New in v1.
> 
> ---
>  drivers/cpufreq/intel_pstate.c |   23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -999,8 +999,11 @@
>  {
>  	static const struct em_data_callback cb
>  			= EM_ADV_DATA_CB(hybrid_active_power, hybrid_get_cost);
> +	struct cpu_cacheinfo *cacheinfo = get_cpu_cacheinfo(cpu);
> +	const struct cpumask *cpumask = cpumask_of(cpu);
>  	struct cpudata *cpudata = all_cpu_data[cpu];
>  	struct device *cpu_dev;
> +	int ret;
>  
>  	/*
>  	 * Registering EM perf domains without enabling asymmetric CPU capacity
> @@ -1014,9 +1017,25 @@
>  	if (!cpu_dev)
>  		return false;
>  
> -	if (em_dev_register_perf_domain(cpu_dev, HYBRID_EM_STATE_COUNT, &cb,
> -					cpumask_of(cpu), false))
> +	if (cacheinfo) {
> +		unsigned int i;
> +
> +		/* Find the L2 cache and the CPUs sharing it. */
> +		for (i = 0; i < cacheinfo->num_leaves; i++) {
> +			if (cacheinfo->info_list[i].level == 2) {
> +				cpumask = &cacheinfo->info_list[i].shared_cpu_map;
> +				break;
> +			}
> +		}
> +	}
> +
> +	ret = em_dev_register_perf_domain(cpu_dev, HYBRID_EM_STATE_COUNT, &cb,
> +					  cpumask, false);
> +	if (ret) {
> +		cpudata->em_registered = ret == -EEXIST;
> +
>  		return false;
> +	}
>  
>  	cpudata->em_registered = true;
>  
> 

debugfs already provides a way to retrieve that information, but with more
complex perf domain constructions like here maybe this would be useful
(maybe it already is):

--->8---

Subject: [PATCH] PM: EM: Print CPUs of perf domains

In preparation for future EAS users who make the relation from CPU
to perf-domain not strictly based on cpufreq policies print the
affected CPUs when registering a perf-domain.

Signed-off-by: Christian Loehle <christian.loehle@....com>
---
 kernel/power/energy_model.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index 99a1ae324c2d..a202968b2ee9 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -627,7 +627,7 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
 	em_cpufreq_update_efficiencies(dev, em_table->state);
 
 	em_debug_create_pd(dev);
-	dev_info(dev, "EM: created perf domain\n");
+	dev_info(dev, "EM: created perf domain for CPUs %*pbl\n", cpumask_pr_args(cpus));
 
 unlock:
 	mutex_unlock(&em_pd_mutex);
-- 
2.34.1