linux-kernel - Re: [PATCH 5/7] x86/resctrl: Add a new "snc_ways" file to the monitoring info directory.

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Date:   Tue, 28 Feb 2023 17:13:32 +0000
From:   James Morse <james.morse@....com>
To:     Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        Jonathan Corbet <corbet@....net>, x86@...nel.org
Cc:     Shaopeng Tan <tan.shaopeng@...itsu.com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Babu Moger <babu.moger@....com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH 5/7] x86/resctrl: Add a new "snc_ways" file to the
 monitoring info directory.

Hi Tony,

On 26/01/2023 18:41, Tony Luck wrote:
> Make it easy for the user to tell if Sub-NUMA Cluster is enabled by
> providing an info/ file.

I think what this is conveying to user-space is 'domain_id_is_numa_node'.

Does user-space need to know the number of ways?

Will this always be a single number, or will it ever be possible to have an SNC=2 and
SNC=1 package in the same system?


Thanks,

James

> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index a0dc64a70d01..392e7a08d083 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -997,6 +997,14 @@ static int rdt_num_rmids_show(struct kernfs_open_file *of,
>  	return 0;
>  }
>  
> +static int rdt_snc_ways_show(struct kernfs_open_file *of,
> +			     struct seq_file *seq, void *v)
> +{
> +	seq_printf(seq, "%d\n", snc_ways);
> +
> +	return 0;
> +}
> +
>  static int rdt_mon_features_show(struct kernfs_open_file *of,
>  				 struct seq_file *seq, void *v)
>  {
> @@ -1451,6 +1459,13 @@ static struct rftype res_common_files[] = {
>  		.seq_show	= rdt_num_rmids_show,
>  		.fflags		= RF_MON_INFO,
>  	},
> +	{
> +		.name		= "snc_ways",
> +		.mode		= 0444,
> +		.kf_ops		= &rdtgroup_kf_single_ops,
> +		.seq_show	= rdt_snc_ways_show,
> +		.fflags		= RF_MON_INFO,
> +	},
>  	{
>  		.name		= "cbm_mask",
>  		.mode		= 0444,