linux-kernel - Re: [RFC PATCH v2 2/3] sched: Introduce cpus_share

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Date:   Tue, 22 Aug 2023 15:58:01 +0800
From:   Aaron Lu <aaron.lu@...el.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC:     Peter Zijlstra <peterz@...radead.org>,
        <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        "Mel Gorman" <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Swapnil Sapkal <Swapnil.Sapkal@....com>,
        "Julien Desfossez" <jdesfossez@...italocean.com>, <x86@...nel.org>
Subject: Re: [RFC PATCH v2 2/3] sched: Introduce cpus_share_l2c

On Sat, Aug 19, 2023 at 08:31:55AM -0400, Mathieu Desnoyers wrote:
> +#ifdef TOPOLOGY_CLUSTER_SYSFS
> +static int cpu_get_l2c_info(int cpu, int *l2c_size, int *l2c_id)
> +{
> +	const struct cpumask *cluster_mask = topology_cluster_cpumask(cpu);
> +
> +	*l2c_size = cpumask_weight(cluster_mask);
> +	*l2c_id = cpumask_first(cluster_mask);
> +	return 0;
> +}
> +#else
> +static int cpu_get_l2c_info(int cpu, int *l2c_size, int *l2c_id)
> +{
> +	return -1;
> +}
> +#endif
> +
>  static void update_top_cache_domain(int cpu)
>  {
>  	struct sched_domain_shared *sds = NULL;
>  	struct sched_domain *sd;
> -	int id = cpu;
> -	int size = 1;
> +	int id = cpu, size = 1, l2c_id, l2c_size;
>  
>  	sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
>  	if (sd) {
> @@ -686,6 +704,14 @@ static void update_top_cache_domain(int cpu)
>  		sds = sd->shared;
>  	}
>  
> +	if (cpu_get_l2c_info(cpu, &l2c_id, &l2c_size)) {

Should be:  cpu_get_l2c_info(cpu, &l2c_size, &l2c_id)

> +		/* Fallback on using LLC. */
> +		l2c_size = size;
> +		l2c_id = id;
> +	}
> +	per_cpu(sd_l2c_size, cpu) = l2c_size;
> +	per_cpu(sd_l2c_id, cpu) = l2c_id;
> +
>  	rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
>  	per_cpu(sd_llc_size, cpu) = size;
>  	per_cpu(sd_llc_id, cpu) = id;
> -- 
> 2.39.2
>