linux-kernel - Re: [PATCH v7 4/8] x86/resctrl: Add comments on RFTYPE flags hierarchy

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Date:   Wed, 16 Aug 2023 10:34:55 -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 v7 4/8] x86/resctrl: Add comments on RFTYPE flags
 hierarchy

Hi Reinette,

On 8/15/23 17:45, Reinette Chatre wrote:
> Hi Babu,
> 
> On 8/11/2023 1:09 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 |   49 ++++++++++++++++++++++++++++++++
>>  1 file changed, 49 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 2051179a3b91..37800724e002 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -240,6 +240,55 @@ 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 (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.)
>> + *
>> + *	info directory structure
>> + *	------------------------------------------------------------------
>> + *	--> RFTYPE_INFO
>> + *	--> <info> directory
>> + *		--> RFTYPE_TOP_INFO
>> + *		    Files: last_cmd_status
>> + *
>> + *		--> RFTYPE_MON_INFO
>> + *		--> <L3_MON> directory
>> + *		    Files: max_threshold_occupancy, mon_features,
>> + *			   num_rmids, mbm_total_bytes_config,
>> + *			   mbm_local_bytes_config
>> + *
> 
> I think the monitor files need the same split as what you did for
> control files in this version. That is, there are some files
> that depend on RFTYPE_MON_INFO and others that depend on
> RFTYPE_MON_INFO | RFTYPE_RES_CACHE. In above it appears that
> all files depend on RFTYPE_MON_INFO only.

ok. Sure.


>> + *		--> RFTYPE_CTRL_INFO
>> + *		    Files: num_closids
>> + *
> 
> Looking at this closer I can see some potential confusion about where these
> files appear. A note saying that these files appear in all sub-directories
> may be helpful because at this point it appears that this file is at the
> same level as the directories.

Sure..

With both these changes. Here is the diff on top of current patch.

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h
b/arch/x86/kernel/cpu/resctrl/internal.h
index 37800724e002..412a9ef98171 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -264,12 +264,16 @@ struct rdtgroup {
  *
  *             --> RFTYPE_MON_INFO
  *             --> <L3_MON> directory
- *                 Files: max_threshold_occupancy, mon_features,
- *                        num_rmids, mbm_total_bytes_config,
- *                        mbm_local_bytes_config
+ *                 Files: mon_features, num_rmids
+ *
+ *                     --> RFTYPE_RES_CACHE
+ *                         Files: max_threshold_occupancy,
+ *                                mbm_total_bytes_config,
+ *                                mbm_local_bytes_config
  *
  *             --> RFTYPE_CTRL_INFO
  *                 Files: num_closids
+ *                        These files appear in all the sub-directories.
  *
  *                     --> RFTYPE_RES_CACHE
  *                     --> <L2,L3> directories


Thanks
Babu

> 
>> + *			--> RFTYPE_RES_CACHE
>> + *			--> <L2,L3> directories
>> + *			    Files: bit_usage, cbm_mask, min_cbm_bits,
>> + *				   shareable_bits
>> + *
>> + *			--> RFTYPE_RES_MB
>> + *			--> <MB,SMBA> directories
>> + *			    Files: bandwidth_gran, delay_linear,
>> + *				   min_bandwidth, thread_throttle_mode
>> + *
>> + *	base directory 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)
>>
>>
> 
> Reinette

-- 
Thanks
Babu Moger