linux-kernel - [RFC v2 PATCH 6/7] x86/resctrl: Display the RMID and COSID for resctrl groups

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Date:   Thu, 2 Feb 2023 15:47:31 -0600
From:   Babu Moger <babu.moger@....com>
To:     <fenghua.yu@...el.com>, <reinette.chatre@...el.com>
CC:     <babu.moger@....com>, <tglx@...utronix.de>, <mingo@...hat.com>,
        <bp@...en8.de>, <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
        <hpa@...or.com>, <corbet@....net>, <linux-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <eranian@...gle.com>,
        <peternewman@...gle.com>
Subject: [RFC v2 PATCH 6/7] x86/resctrl: Display the RMID and COSID for
 resctrl groups

When a user creates a control or monitor group, the CLOSID or RMID
are not visible to the user. These are architecturally defined entities.
There is no harm in displaying these in resctrl groups. Sometimes it
can help to debug the issues.

Add CLOSID and RMID to the control/monitor groups display in resctrl
interface.

$cat /sys/fs/resctrl/clos1/closid
1
$cat /sys/fs/resctrl/mon_groups/mon1/rmid
3

Signed-off-by: Babu Moger <babu.moger@....com>
---
 Documentation/x86/resctrl.rst          |   17 ++++++++++++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |   44 ++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/Documentation/x86/resctrl.rst b/Documentation/x86/resctrl.rst
index 2c013c5d45fd..de332c242523 100644
--- a/Documentation/x86/resctrl.rst
+++ b/Documentation/x86/resctrl.rst
@@ -321,6 +321,15 @@ All groups contain the following files:
 	Just like "cpus", only using ranges of CPUs instead of bitmasks.
 
 
+"rmid":
+        Available only with debug option.Reading this file shows the
+        resource monitoring id (RMID) for monitoring the resource
+        utilization. Monitoring is performed by tagging each core(or
+        thread) or process via a Resource Monitoring ID (RMID). Kernel
+        assigns a new RMID when a group is created depending on the
+        available RMIDs. Multiple cores(or threads) or processes can
+        share a same RMID in a resctrl domain.
+
 When control is enabled all CTRL_MON groups will also contain:
 
 "schemata":
@@ -342,6 +351,14 @@ When control is enabled all CTRL_MON groups will also contain:
 	file. On successful pseudo-locked region creation the mode will
 	automatically change to "pseudo-locked".
 
+"closid":
+        Available only with debug option. Reading this file shows the
+        Class of Service (CLOS) id which acts as a resource control tag
+        on which the resources can be throttled. Kernel assigns a new
+        CLOSID a control group is created depending on the available
+        CLOSIDs. Multiple cores(or threads) or processes can share a
+        same CLOSID in a resctrl domain.
+
 When monitoring is enabled all MON groups will also contain:
 
 "mon_data":
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 9b7813aa6baf..c35d91b04de6 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -760,6 +760,38 @@ static int rdtgroup_tasks_show(struct kernfs_open_file *of,
 	return ret;
 }
 
+static int rdtgroup_closid_show(struct kernfs_open_file *of,
+				struct seq_file *s, void *v)
+{
+	struct rdtgroup *rdtgrp;
+	int ret = 0;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (rdtgrp)
+		seq_printf(s, "%u\n", rdtgrp->closid);
+	else
+		ret = -ENOENT;
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret;
+}
+
+static int rdtgroup_rmid_show(struct kernfs_open_file *of,
+			      struct seq_file *s, void *v)
+{
+	struct rdtgroup *rdtgrp;
+	int ret = 0;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (rdtgrp)
+		seq_printf(s, "%u\n", rdtgrp->mon.rmid);
+	else
+		ret = -ENOENT;
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret;
+}
+
 #ifdef CONFIG_PROC_CPU_RESCTRL
 
 /*
@@ -1844,6 +1876,18 @@ static struct rftype res_common_files[] = {
 		.seq_show	= rdtgroup_size_show,
 		.fflags		= RFTYPE_BASE_CTRL,
 	},
+	{
+		.name		= "closid",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdtgroup_closid_show,
+	},
+	{
+		.name		= "rmid",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdtgroup_rmid_show,
+	},
 
 };