linux-kernel - Re: [PATCH v5 4/8] x86/resctrl: Add comments on RFTYPE flags hierarchy

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Date:   Tue, 11 Jul 2023 18:19:06 -0500
From:   "Moger, Babu" <babu.moger@....com>
To:     Reinette Chatre <reinette.chatre@...el.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 v5 4/8] x86/resctrl: Add comments on RFTYPE flags
 hierarchy

Hi Reinette,

On 7/7/23 16:39, Reinette Chatre wrote:
> Hi Babu,
> 
> On 6/1/2023 12:01 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>
>> ---
>>  arch/x86/kernel/cpu/resctrl/internal.h |   45 ++++++++++++++++++++++++++++++++
>>  1 file changed, 45 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 2051179a3b91..c20cd6acb7a3 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -240,6 +240,51 @@ struct rdtgroup {
>>  
>>  /*
>>   * Define the file type flags for base and info directories.
>> + *
>> + * RESCTRL filesystem has two main components
>> + *   a. info
>> + *   b. base
>> + *
>> + * /sys/fs/resctrl/
>> + *     |
>> + *     --> info (directory and provides details on control
>> + *     |         and monitoring resources)
>> + *     |
>> + *     --> base (Lists the files and information to interact with control
>> + *               or monitor groups. Provides details on default control
>> + *               group when filesystem is created. There is no directory
>> + *               with name base)
>> + *
> 
> In the above I think it may help to split the comment into two parts:
> (a) which directory/directories are referred to, and (b) which files can be
> found in the directory/directories.
> 
> For example,
> 
> --> info (Top level directory named "info". Contains files that provide
>           details on control and monitoring resources.)
> 
> --> base (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.)
> 
> Please feel free to improve.

Looks good.

> 
>> + *     info structure
>> + *    -------------------------------------------------------------
>> + *    --> RFTYPE_INFO
>> + *        --> <info> directory
>> + *            --> RFTYPE_TOP_INFO
>> + *                Files: last_cmd_status
>> + *
>> + *        --> RFTYPE_MON_INFO
>> + *            --> <L3_MON> directory
>> + *                 Files: max_threshold_occupancy, mbm_local_bytes_config,
>> + *                        mbm_total_bytes_config, mon_features, num_rmids
>> + *
>> + *        --> RFTYPE_CTRL_INFO
>> + *            --> RFTYPE_RES_CACHE
>> + *                --> <L2/L3> directory
> 
> Maybe a nitpick but I wonder if it should be "L2,L3" to not create impression
> that it is either/or?

Sure.
> 
>> + *                     Files: bit_usage, cbm_mask, min_cbm_bits,
>> + *                            num_closids, shareable_bits
>> + *
>> + *            --> RFTYPE_RES_MB
>> + *                --> <MB/SMBA> directory
> 
> Same here ... perhaps "MB,SMBA"

Sure.
> 
>> + *                     Files: bandwidth_gran, delay_linear, min_bandwidth,
>> + *                            num_closids
> 
> Missing thread_throttle_mode

Will add it.
> 
>> + *
>> + *     base structure
>> + *     -----------------------------------------------------------
>> + *     --> RFTYPE_BASE (Files common for both MON and CTRL groups)
>> + *         Files: cpus, cpus_list, tasks
>> + *
>> + *     --> RFTYPE_CTRL_BASE (Files only for CTRL group)
>> + *         Files: mode, schemata, size
>>   */
>>  #define RFTYPE_INFO			BIT(0)
>>  #define RFTYPE_BASE			BIT(1)
>>
>>
> 
> I think this is a helpful addition. Thanks for doing this.

Sure. Welcome.Thanks
Babu Moger