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fs/resctrl: Add resctrl file to display number of assignable counters

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The "mbm_event" counter assignment mode allows users to assign a hardware
counter to an RMID, event pair and monitor bandwidth usage as long as it is
assigned.  The hardware continues to track the assigned counter until it is
explicitly unassigned by the user.

Create 'num_mbm_cntrs' resctrl file that displays the number of counters
supported in each domain. 'num_mbm_cntrs' is only visible to user space when
the system supports "mbm_event" mode.

Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com
This commit is contained in:
Babu Moger
2025-09-05 16:34:10 -05:00
committed by Borislav Petkov (AMD)
parent 3b497c3f4f
commit 8c793336ea
4 changed files with 45 additions and 0 deletions
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11
Documentation/filesystems/resctrl.rst
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@@ -288,6 +288,17 @@ with the following files:
result in misleading values or display "Unavailable" if no counter is assigned
to the event.
"num_mbm_cntrs":
The maximum number of counters (total of available and assigned counters) in
each domain when the system supports mbm_event mode.
For example, on a system with maximum of 32 memory bandwidth monitoring
counters in each of its L3 domains:
::
# cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
0=32;1=32
"max_threshold_occupancy":
Read/write file provides the largest value (in
bytes) at which a previously used LLC_occupancy

2
fs/resctrl/internal.h
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@@ -386,6 +386,8 @@ void *rdt_kn_parent_priv(struct kernfs_node *kn);
int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of, struct seq_file *s, void *v);
int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of, struct seq_file *s, void *v);
#ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);

26
fs/resctrl/monitor.c
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@@ -912,6 +912,30 @@ int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of,
return 0;
}
int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of,
struct seq_file *s, void *v)
{
struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
struct rdt_mon_domain *dom;
bool sep = false;
cpus_read_lock();
mutex_lock(&rdtgroup_mutex);
list_for_each_entry(dom, &r->mon_domains, hdr.list) {
if (sep)
seq_putc(s, ';');
seq_printf(s, "%d=%d", dom->hdr.id, r->mon.num_mbm_cntrs);
sep = true;
}
seq_putc(s, '\n');
mutex_unlock(&rdtgroup_mutex);
cpus_read_unlock();
return 0;
}
/**
* resctrl_mon_resource_init() - Initialise global monitoring structures.
*
@@ -957,6 +981,8 @@ int resctrl_mon_resource_init(void)
resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID);
if (!resctrl_is_mon_event_enabled(QOS_L3_MBM_LOCAL_EVENT_ID))
resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID);
resctrl_file_fflags_init("num_mbm_cntrs",
RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
}
return 0;

6
fs/resctrl/rdtgroup.c
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@@ -1836,6 +1836,12 @@ static struct rftype res_common_files[] = {
.seq_show = rdt_default_ctrl_show,
.fflags = RFTYPE_CTRL_INFO | RFTYPE_RES_CACHE,
},
{
.name = "num_mbm_cntrs",
.mode = 0444,
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = resctrl_num_mbm_cntrs_show,
},
{
.name = "min_cbm_bits",
.mode = 0444,