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

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Message-ID: <20231013202602.2492645-5-babu.moger@amd.com>
Date:   Fri, 13 Oct 2023 15:25:56 -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>,
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        <sandipan.das@....com>, <tony.luck@...el.com>,
        <james.morse@....com>, <linux-doc@...r.kernel.org>,
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        <jarkko@...nel.org>, <adrian.hunter@...el.com>,
        <quic_jiles@...cinc.com>, <peternewman@...gle.com>
Subject: [PATCH v13 04/10] 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>
---
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
+
+	   (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
+
+	-> 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
+
+	-> 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
 -------------------------
 
-- 
2.34.1