linux-kernel - Re: [PATCH 10/24] x86/resctrl: Move the schema names into struct resctrl

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Date:   Tue, 17 Nov 2020 15:11:21 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        shameerali.kolothum.thodi@...wei.com,
        Jamie Iles <jamie@...iainc.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>
Subject: Re: [PATCH 10/24] x86/resctrl: Move the schema names into struct
 resctrl_schema

Hi James,

On 10/30/2020 9:11 AM, James Morse wrote:
> Move the names used for the schemata file out of the resource and
> into struct resctrl_schema. This allows one resource to have two
> different names, based on the other schema properties.
> 
> This patch copies the names, eventually resctrl will generate them.

Please remove "This patch".

> 
> Remove the arch code's max_name_width, this is now resctrl's
> problem.
> 
> Signed-off-by: James Morse <james.morse@....com>
> ---
>   arch/x86/kernel/cpu/resctrl/core.c        |  9 ++-------
>   arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 10 +++-------
>   arch/x86/kernel/cpu/resctrl/internal.h    |  2 +-
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 17 ++++++++++++-----
>   include/linux/resctrl.h                   |  7 +++++++
>   5 files changed, 25 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 1ed5e04031e6..cda071009fed 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -37,10 +37,10 @@ DEFINE_MUTEX(rdtgroup_mutex);
>   DEFINE_PER_CPU(struct resctrl_pqr_state, pqr_state);
>   
>   /*
> - * Used to store the max resource name width and max resource data width
> + * Used to store the max resource data width
>    * to display the schemata in a tabular format
>    */
> -int max_name_width, max_data_width;
> +int max_data_width;
>   
>   /*
>    * Global boolean for rdt_alloc which is true if any
> @@ -776,13 +776,8 @@ static int resctrl_offline_cpu(unsigned int cpu)
>   static __init void rdt_init_padding(void)
>   {
>   	struct rdt_resource *r;
> -	int cl;
>   
>   	for_each_alloc_capable_rdt_resource(r) {
> -		cl = strlen(r->name);
> -		if (cl > max_name_width)
> -			max_name_width = cl;
> -
>   		if (r->data_width > max_data_width)
>   			max_data_width = r->data_width;
>   	}

The original code determines the maximum width based on resources 
supported by the platform.

> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index a65ff53394ed..28d69c78c29e 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c

...

> @@ -391,7 +389,7 @@ static void show_doms(struct seq_file *s, struct resctrl_schema *schema, int clo
>   	bool sep = false;
>   	u32 ctrl_val;
>   
> -	seq_printf(s, "%*s:", max_name_width, r->name);
> +	seq_printf(s, "%*s:", RESCTRL_NAME_LEN, schema->name);

 From what I understand this changes what some users will see. In the 
original code the "max_name_width" is computed based on the maximum 
length of resources supported. Systems that only support MBA would thus 
show a schemata of:

MB:0=100;1=100

I expect the above change would change the output to:
     MB:0=100;1=100


>   	list_for_each_entry(dom, &r->domains, list) {
>   		hw_dom = resctrl_to_arch_dom(dom);
>   		if (sep)

...


> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 8a12f4128209..9f71f0238239 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -15,6 +15,11 @@ int proc_resctrl_show(struct seq_file *m,
>   
>   #endif
>   
> +/*
> + * The longest name we expect in the schemata file:
> + */
> +#define RESCTRL_NAME_LEN	7
> +
>   enum resctrl_conf_type {
>   	CDP_BOTH,
>   	CDP_CODE,
> @@ -172,12 +177,14 @@ struct rdt_resource {
>   
>   /**
>    * @list:	Member of resctrl's schema list
> + * @names:	Name to use in "schemata" file

s/names/name/?

>    * @conf_type:	Type of configuration, e.g. code/data/both
>    * @res:	The rdt_resource for this entry
>    * @num_closid	Number of CLOSIDs available for this resource
>    */
>   struct resctrl_schema {
>   	struct list_head		list;
> +	char				name[RESCTRL_NAME_LEN];
>   	enum resctrl_conf_type		conf_type;
>   	struct rdt_resource		*res;
>   	u32				num_closid;
> 


Reinette