linux-kernel - Re: [PATCH 06/24] x86/resctrl: Store the effective num

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Message-ID: <14fa276a-ce44-07f4-203e-d1c8f5967b0b@intel.com>
Date:   Tue, 17 Nov 2020 14:04:29 -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 06/24] x86/resctrl: Store the effective num_closid in the
 schema

Hi James,

On 10/30/2020 9:11 AM, James Morse wrote:
> resctrl_schema holds properties that vary with the style of configuration
> that resctrl applies to a resource.
> 
> Once the arch code has a single resource per cache that can be configured,
> resctrl will need to keep track of the num_closid itself.
> 
> Add num_closid to resctrl_schema. Change callers like
> rdtgroup_schemata_show() to walk the schema instead.

This is a significant patch in that it introduces a second num_closid 
available for code to use. Even so, the commit message is treating it 
quite nonchalantly ... essentially stating that "here is a new closid 
and change some code to use it".

Could you please elaborate how the callers needing to "walk the schema 
instead" were chosen?

This seems almost a revert of the earlier patch that introduced the 
helper and I wonder if it may not make this easier to understand if 
these areas do not receive the temporary change to use that helper.

> 
> Signed-off-by: James Morse <james.morse@....com>
> ---
>   arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 13 ++++++++-----
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 11 +++++------
>   include/linux/resctrl.h                   |  2 ++
>   3 files changed, 15 insertions(+), 11 deletions(-)
> 

...

> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index de6cbc725753..b32152968bca 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -166,10 +166,12 @@ struct rdt_resource {
>   /**
>    * @list:	Member of resctrl's schema list
>    * @res:	The rdt_resource for this entry
> + * @num_closid	Number of CLOSIDs available for this resource

Missing a ":"?

>    */
>   struct resctrl_schema {
>   	struct list_head		list;
>   	struct rdt_resource		*res;
> +	u32				num_closid;
>   };
>   
>   /* The number of closid supported by this resource regardless of CDP */
> 

Reinette