Hi Reinette,
On 10/15/2024 10:36 PM, Reinette Chatre wrote:
Hi Babu,
On 10/9/24 10:39 AM, Babu Moger wrote:
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 will reset when mbm_assign_mode is changed.
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
...
---
Documentation/arch/x86/resctrl.rst | 15 ++++++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 75 +++++++++++++++++++++++++-
2 files changed, 89 insertions(+), 1 deletion(-)
diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 99ee9c87952b..d9574078f735 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -291,6 +291,21 @@ with the following files:
that case reading the mbm_total_bytes and mbm_local_bytes may report
'Unavailable' if there is no counter associated with that group.
+ * To enable "mbm_cntr_assign" mode:
+ ::
+
+ # echo "mbm_cntr_assign" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
extra spaces
Sure.
+
+ * To enable default monitoring mode:
+ ::
+
+ # echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
extra spaces
Sure
+
+ The MBM events (mbm_total_bytes and/or mbm_local_bytes) associated counters
I did ask you not to copy the text verbatim
https://lore.kernel.org/all/b38c93bf-4650-45d1-9aca-8b4c4d425886@xxxxxxxxx/
Outch Yea.
The MBM events (mbm_total_bytes and/or mbm_local_bytes) associated with
counters may reset when mbm_assign_mode is changed.
+ may reset when the mode is changed. Moving to mbm_cntr_assign mode will
+ require users to assign the counters to the events. Otherwise, the MBM
"will require" -> "require"
+ event counters will return "Unassigned" when read.
+
"num_mbm_cntrs":
The number of monitoring counters available for assignment when the
architecture supports mbm_cntr_assign mode.
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index cb2c60c0319e..88eda3cf5c82 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -888,6 +888,78 @@ static int rdtgroup_mbm_assign_mode_show(struct kernfs_open_file *of,
return 0;
}
+static void mbm_cntr_reset(struct rdt_resource *r)
+{
+ struct rdtgroup *prgrp, *crgrp;
+ struct rdt_mon_domain *dom;
+
+ /*
+ * Hardware counters will reset after switching the monitor mode.
+ * Reset the architectural state so that reading of hardware
+ * counter is not considered as an overflow in the next update.
+ * Also reset the domain counter bitmap.
+ */
+ list_for_each_entry(dom, &r->mon_domains, hdr.list) {
+ bitmap_zero(dom->mbm_cntr_map, r->mon.num_mbm_cntrs);
+ resctrl_arch_reset_rmid_all(r, dom);
+ }
+
+ /* Reset global MBM counter map */
+ bitmap_fill(r->mon.mbm_cntr_free_map, r->mon.num_mbm_cntrs);
+
+ /* Reset the cntr_id's for all the monitor groups */
+ list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
+ prgrp->mon.cntr_id[0] = MON_CNTR_UNSET;
+ prgrp->mon.cntr_id[1] = MON_CNTR_UNSET;
+ list_for_each_entry(crgrp, &prgrp->mon.crdtgrp_list,
+ mon.crdtgrp_list) {
+ crgrp->mon.cntr_id[0] = MON_CNTR_UNSET;
+ crgrp->mon.cntr_id[1] = MON_CNTR_UNSET;
+ }
Please use MBM_EVENT_ARRAY_INDEX
Sure.
+ }
+}
+
+static ssize_t rdtgroup_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")) {
+ enable = 1;
+ } else {
+ ret = -EINVAL;
+ rdt_last_cmd_puts("Unsupported assign mode\n");
+ goto write_exit;
+ }
Please keep two things in mind:
* this file is always accessible, whether platform supports assignable
counters or not.
* this is resctrl fs code.
So, considering above, how should user interpret the "Unsupported assign mode"?
Shouldn't it also return this error if a user attempts to enable
"mbm_cntr_assign" on a platform that does not support this mode?
+
+ if (enable != resctrl_arch_mbm_cntr_assign_enabled(r)) {
resctrl_arch_mbm_cntr_assign_enabled() returns true if mbm_cntr_assign
mode is enabled, but when it returns false it could mean different things:
platform supports mbm_cntr_assign mode, but it is disabled, or platform
does not support mbm_cntr_assign mode.
resctrl fs should not rely on all archs to duplicate the all the checking done
in resctrl_arch_mbm_cntr_assign_set(). It should never ask arch to enable a mode
that it knows the platform is not capable of.
Agree. This should take care of it. Good catch.
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;
}
+ 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;
+}
+
static int rdtgroup_num_mbm_cntrs_show(struct kernfs_open_file *of,
struct seq_file *s, void *v)
{
@@ -2115,9 +2187,10 @@ static struct rftype res_common_files[] = {
},
{
.name = "mbm_assign_mode",
- .mode = 0444,
+ .mode = 0644,
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = rdtgroup_mbm_assign_mode_show,
+ .write = rdtgroup_mbm_assign_mode_write,
.fflags = RFTYPE_MON_INFO,
},
{
Reinette
--
- Babu Moger
