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

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Date:   Fri, 11 Aug 2023 15:09:45 -0500
From:   Babu Moger <babu.moger@....com>
To:     <corbet@....net>, <reinette.chatre@...el.com>,
        <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>, <babu.moger@....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>,
        <pawan.kumar.gupta@...ux.intel.com>, <jarkko@...nel.org>,
        <adrian.hunter@...el.com>, <quic_jiles@...cinc.com>,
        <peternewman@...gle.com>, <babu.moger@....com>
Subject: [PATCH v7 4/8] x86/resctrl: Add comments on RFTYPE flags hierarchy

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
+ *
+ *		--> RFTYPE_CTRL_INFO
+ *		    Files: num_closids
+ *
+ *			--> 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)