[PATCH v11 6/8] x86/resctrl: Add "mba_MBps_event" file to CTRL_MON directories

Tony Luck
2024-12-06T16:31:58Z

The "mba_MBps" mount option provides an alternate method to
control memory bandwidth. Instead of specifying allowable
bandwidth as a percentage of maximum possible, the user
provides a MiB/s limit value.

In preparation to allow the user to pick the memory bandwidth
monitoring event used as input to the feedback loop, provide
a file in each CTRL_MON group directory that shows the event
currently in use. Note that this file is only visible when
the "mba_MBps" mount option is in use.

Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
arch/x86/kernel/cpu/resctrl/internal.h | 2 ++
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 30 +++++++++++++++++++++++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 10 ++++++++
3 files changed, 42 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 485800055a7d..ce10a883ecf8 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -609,6 +609,8 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off);
int rdtgroup_schemata_show(struct kernfs_open_file *of,
struct seq_file *s, void *v);
+int rdtgroup_mba_mbps_event_show(struct kernfs_open_file *of,
+ struct seq_file *s, void *v);
bool rdtgroup_cbm_overlaps(struct resctrl_schema *s, struct rdt_ctrl_domain *d,
unsigned long cbm, int closid, bool exclusive);
unsigned int rdtgroup_cbm_to_size(struct rdt_resource *r, struct rdt_ctrl_domain *d,
diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 200d89a64027..5fa37b4ecc7a 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -518,6 +518,36 @@ static int smp_mon_event_count(void *arg)
return 0;
}

+int rdtgroup_mba_mbps_event_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) {
+ switch (rdtgrp->mba_mbps_event) {
+ case QOS_L3_MBM_LOCAL_EVENT_ID:
+ seq_puts(s, "mbm_local_bytes\n");
+ break;
+ case QOS_L3_MBM_TOTAL_EVENT_ID:
+ seq_puts(s, "mbm_total_bytes\n");
+ break;
+ default:
+ pr_warn_once("Bad event %d\n", rdtgrp->mba_mbps_event);
+ ret = -EINVAL;
+ break;
+ }
+ } else {
+ ret = -ENOENT;
+ }
+
+ rdtgroup_kn_unlock(of->kn);
+
+ return ret;
+}
+
void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
cpumask_t *cpumask, int evtid, int first)
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 0659b8e2a71b..6eb930b8bdfd 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1950,6 +1950,12 @@ static struct rftype res_common_files[] = {
.seq_show = rdtgroup_schemata_show,
.fflags = RFTYPE_CTRL_BASE,
},
+ {
+ .name = "mba_MBps_event",
+ .mode = 0444,
+ .kf_ops = &rdtgroup_kf_single_ops,
+ .seq_show = rdtgroup_mba_mbps_event_show,
+ },
{
.name = "mode",
.mode = 0644,
@@ -2355,6 +2361,7 @@ static int set_mba_sc(bool mba_sc)
struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
u32 num_closid = resctrl_arch_get_num_closid(r);
struct rdt_ctrl_domain *d;
+ unsigned long fflags;
int i;

if (!supports_mba_mbps() || mba_sc == is_mba_sc(r))
@@ -2369,6 +2376,9 @@ static int set_mba_sc(bool mba_sc)
d->mbps_val[i] = MBA_MAX_MBPS;
}

+ fflags = mba_sc ? RFTYPE_CTRL_BASE | RFTYPE_MON_BASE : 0;
+ resctrl_file_fflags_init("mba_MBps_event", fflags);
+
return 0;
}

--
2.47.0