linux-kernel - Re: [PATCH v13 04/10] x86/resctrl: Add comments on RFTYPE flags hierarchy

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Message-ID: <d4a33013-0448-4c36-a168-b3a953024962@intel.com>
Date:   Fri, 13 Oct 2023 14:23:56 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Babu Moger <babu.moger@....com>, <corbet@....net>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <fenghua.yu@...el.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <akpm@...ux-foundation.org>, <quic_neeraju@...cinc.com>,
        <rdunlap@...radead.org>, <damien.lemoal@...nsource.wdc.com>,
        <songmuchun@...edance.com>, <peterz@...radead.org>,
        <jpoimboe@...nel.org>, <pbonzini@...hat.com>,
        <chang.seok.bae@...el.com>, <pawan.kumar.gupta@...ux.intel.com>,
        <jmattson@...gle.com>, <daniel.sneddon@...ux.intel.com>,
        <sandipan.das@....com>, <tony.luck@...el.com>,
        <james.morse@....com>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bagasdotme@...il.com>,
        <eranian@...gle.com>, <christophe.leroy@...roup.eu>,
        <jarkko@...nel.org>, <adrian.hunter@...el.com>,
        <quic_jiles@...cinc.com>, <peternewman@...gle.com>
Subject: Re: [PATCH v13 04/10] x86/resctrl: Add comments on RFTYPE flags
 hierarchy

Hi Babu,

On 10/13/2023 1:25 PM, Babu Moger wrote:
> resctrl uses RFTYPE flags for creating resctrl directory structure.
> 
> Definitions and directory structures are not documented. Add
> comments to improve the readability and help future additions.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v13: Fixed the format issues in the documentation. Needed few minor format
>      changes to address the syntax issues.(Reinette)
>      Removed "Reviewed-by and Tested-by" flags as the patch has changed.
> 
> v12: Moved the comments from arch/x86/kernel/cpu/resctrl/internal.h
>      to Documentation/arch/x86/resctrl.rst. (Boris)
> ---
>  Documentation/arch/x86/resctrl.rst | 64 ++++++++++++++++++++++++++++++
>  1 file changed, 64 insertions(+)
> 
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 178ab1d8f747..1163da74f734 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -369,6 +369,70 @@ When monitoring is enabled all MON groups will also contain:
>  	the sum for all tasks in the CTRL_MON group and all tasks in
>  	MON groups. Please see example section for more details on usage.
>  
> +RESCTRL filesystem implementation notes
> +=======================================
> +RESCTRL filesystem has two main components
> +	a. info
> +	b. base
> +
> +	/sys/fs/resctrl/
> +	|
> +	-> info
> +	|
> +	|  (Top level directory named "info". Contains files that
> +	|   provide details on control and monitoring resources")
> +	|
> +	-> base
> +

Could you please do a "make htmldocs" and then ensure that the output looks sane?
The resulting output does not look right to me. For example, the above turns into
a single line that looks like:

/sys/fs/resctrl/ | -> info | | (Top level directory named "info". Contains files that | provide details on control and monitoring resources") | -> base


The spacing also looks off when viewing this in html.

> +	   (Root directory associated with default resource group as
> +	    well as directories created by user for MON and CTRL groups.
> +	    Contains files to interact with MON and CTRL groups)
> +
> +	Note: resctrl uses flags for files, not for directories.
> +	      Directories are created based on the resource type. Added
> +	      directories below for better understanding. The RFTYPE flags
> +	      are defined in arch/x86/kernel/cpu/resctrl/internal.h.
> +
> +	info directory structure
> +

You removed the separator in order to pass the syntax issue but now there is
no indication that this is a heading and the content becomes harder to understand.

> +	-> RFTYPE_INFO
> +	   Directory: info
> +
> +	-> RFTYPE_TOP (Files in top level of info directory)
> +	   File: last_cmd_status
> +
> +	-> RFTYPE_MON (Files for all monitoring resources)
> +	   Directory: L3_MON
> +	       Files: mon_features, num_rmids
> +
> +		-> RFTYPE_RES_CACHE (Files for cache monitoring resources)
> +		   Directory: L3_MON
> +		       Files: max_threshold_occupancy,
> +		              mbm_total_bytes_config,
> +		              mbm_local_bytes_config
> +
> +	-> RFTYPE_CTRL (Files for all control resources)
> +	   Directories: L2, L3, MB, SMBA, L2CODE, L2DATA, L3CODE, L3DATA
> +	          File: num_closids
> +
> +		-> RFTYPE_RES_CACHE (Files for cache control resources)
> +		   Directories: L2, L3, L2CODE, L2DATA, L3CODE, L3DATA
> +		         Files: bit_usage, cbm_mask, min_cbm_bits,
> +		                 shareable_bits
> +
> +		-> RFTYPE_RES_MB (Files for memory control resources)
> +		   Directories: MB, SMBA
> +		         Files: bandwidth_gran, delay_linear,
> +		                 min_bandwidth, thread_throttle_mode
> +
> +	base directory structure
> +

Same here.

> +	-> RFTYPE_BASE (Files common for both MON and CTRL groups)
> +	   Files: cpus, cpus_list, tasks
> +
> +		-> RFTYPE_CTRL (Files for CTRL group)
> +		   Files: mode, schemata, size
> +
>  Resource allocation rules
>  -------------------------
>  

Reinette