Resctrl subsystem can support two monitoring modes, 'mbm_cntr_assign' or
'default'. In mbm_cntr_assign, monitoring event can only accumulate data
while it is backed by a hardware counter. In 'default' mode, resctrl
assumes there is a hardware counter for each event within every CTRL_MON
and MON group.
Introduce interface to switch between mbm_cntr_assign and default modes.
$ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
[mbm_cntr_assign]
default
To enable the "mbm_cntr_assign" mode:
$ echo "mbm_cntr_assign" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
To enable the default monitoring mode:
$ echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
MBM event counters are automatically reset as part of changing the mode.
Clear both architectural and non-architectural event states to prevent
overflow conditions during the next event read.
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v11: Changed the name of the function rdtgroup_mbm_assign_mode_write() to
resctrl_mbm_assign_mode_write().
Rewrote the commit message with context.
Added few more details in resctrl.rst about mbm_cntr_assign mode.
Re-arranged the text in resctrl.rst file.
v10: The call mbm_cntr_reset() has been moved to earlier patch.
Minor documentation update.
v9: Fixed extra spaces in user documentation.
Fixed problem changing the mode to mbm_cntr_assign mode when it is
not supported. Added extra checks to detect if systems supports it.
Used the rdtgroup_cntr_id_init to initialize cntr_id.
v8: Reset the internal counters after mbm_cntr_assign mode is changed.
Renamed rdtgroup_mbm_cntr_reset() to mbm_cntr_reset()
Updated the documentation to make text generic.
v7: Changed the interface name to mbm_assign_mode.
Removed the references of ABMC.
Added the changes to reset global and domain bitmaps.
Added the changes to reset rmid.
v6: Changed the mode name to mbm_cntr_assign.
Moved all the FS related code here.
Added changes to reset mbm_cntr_map and resctrl group counters.
v5: Change log and mode description text correction.
v4: Minor commit text changes. Keep the default to ABMC when supported.
Fixed comments to reflect changed interface "mbm_mode".
v3: New patch to address the review comments from upstream.
---
Documentation/arch/x86/resctrl.rst | 25 ++++++++++++-
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 50 +++++++++++++++++++++++++-
2 files changed, 73 insertions(+), 2 deletions(-)
diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 072b15550ff7..5d18c4c8bc48 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -259,7 +259,10 @@ with the following files:
"mbm_assign_mode":
Reports the list of monitoring modes supported. The enclosed brackets
- indicate which mode is enabled.
+ indicate which mode is enabled. The MBM events (mbm_total_bytes and/or
+ mbm_local_bytes) associated with counters may reset when "mbm_assign_mode"
+ is changed.
+
::
# cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
@@ -275,6 +278,16 @@ with the following files:
available is described in the "num_mbm_cntrs" file. Changing the mode
may cause all counters on a resource to reset.
+ Moving to mbm_cntr_assign mode require users to assign the counters to
+ the events. Otherwise, the MBM event counters will return "Unassigned"
+ when read.
+
+ The mode is beneficial for AMD platforms that support more CTRL_MON
+ and MON groups than available hardware counters. By default, this
+ feature is enabled on AMD platforms with the ABMC (Assignable Bandwidth
+ Monitoring Counters) capability, ensuring counters remain assigned even
+ when the corresponding RMID is not actively used by any processor.
+
"default":
In default mode, resctrl assumes there is a hardware counter for each
@@ -283,6 +296,16 @@ with the following files:
"mbm_total_bytes" or "mbm_local_bytes" will report 'Unavailable' if
there is no counter associated with that event.
+ * To enable "mbm_cntr_assign" mode:
+ ::
+
+ # echo "mbm_cntr_assign" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
+
+ * To enable default monitoring mode:
+ ::
+
+ # echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
+
"num_mbm_cntrs":
The number of monitoring counters available for assignment when the
system supports mbm_cntr_assign mode.
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index f61f0cd032ef..6922173c4f8f 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -928,6 +928,53 @@ static int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of,
return ret;
}
+static ssize_t resctrl_mbm_assign_mode_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct rdt_resource *r = of->kn->parent->priv;
+ int ret = 0;
+ bool enable;
+
+ /* Valid input requires a trailing newline */
+ if (nbytes == 0 || buf[nbytes - 1] != '\n')
+ return -EINVAL;
+
+ buf[nbytes - 1] = '\0';
+
+ cpus_read_lock();
+ mutex_lock(&rdtgroup_mutex);
+
+ rdt_last_cmd_clear();
+
+ if (!strcmp(buf, "default")) {
+ enable = 0;
+ } else if (!strcmp(buf, "mbm_cntr_assign")) {
+ if (r->mon.mbm_cntr_assignable) {
+ enable = 1;
+ } else {
+ ret = -EINVAL;
+ rdt_last_cmd_puts("mbm_cntr_assign mode is not supported\n");
+ goto write_exit;
+ }
+ } else {
+ ret = -EINVAL;
+ rdt_last_cmd_puts("Unsupported assign mode\n");
+ goto write_exit;
+ }
+
+ if (enable != resctrl_arch_mbm_cntr_assign_enabled(r)) {
+ ret = resctrl_arch_mbm_cntr_assign_set(r, enable);
+ if (!ret)
+ mbm_cntr_reset(r);
+ }
+
+write_exit:
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+
+ return ret ?: nbytes;
+}
+
#ifdef CONFIG_PROC_CPU_RESCTRL
/*
@@ -1945,9 +1992,10 @@ static struct rftype res_common_files[] = {
},
{
.name = "mbm_assign_mode",
- .mode = 0444,
+ .mode = 0644,
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = resctrl_mbm_assign_mode_show,
+ .write = resctrl_mbm_assign_mode_write,
.fflags = RFTYPE_MON_INFO,
},
{
--
2.34.1
