Hi Babu,
On 6/13/25 2:05 PM, Babu Moger wrote:
> Resctrl subsystem can support two monitoring modes, "mbm_event" or
> "default". In mbm_event mode, 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_event and default modes.
"Introduce interface" -> "Introduce mbm_assign_mode resctrl file"
>
> Example:
> To list the MBM monitor modes supported:
> $ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> [mbm_event]
> default
>
> To enable the "mbm_event" monitoring mode:
> $ echo "mbm_event" > /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. Also clear assignable
> counter configuration on all the domains.
>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
...
> ---
> Documentation/filesystems/resctrl.rst | 23 +++++++-
> fs/resctrl/internal.h | 2 +
> fs/resctrl/monitor.c | 27 ++++++++++
> fs/resctrl/rdtgroup.c | 78 +++++++++++++++++++++++++--
> 4 files changed, 126 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index cd82c2966ed7..7e62c7fdcefa 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -259,7 +259,9 @@ with the following files:
>
> "mbm_assign_mode":
> The supported monitoring modes. The enclosed brackets indicate which mode
> - is enabled.
> + is enabled. The MBM events (mbm_total_bytes and/or mbm_local_bytes) associated
Since there may be more events in future I think the "(mbm_total_bytes and/or
mbm_local_bytes)" can be dropped.
> + with counters may reset when "mbm_assign_mode" is changed.
> +
> ::
>
> # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> @@ -279,6 +281,15 @@ with the following files:
> of counters available is described in the "num_mbm_cntrs" file. Changing the
> mode may cause all counters on the resource to reset.
>
> + Moving to mbm_event mode require users to assign the counters to the events.
"Moving to mbm_event mode require" -> "mbm_event counter assignment mode requires"
> + 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
> @@ -288,6 +299,16 @@ with the following files:
> result in misleading values or display "Unavailable" if no counter is assigned
> to the event.
>
> + * To enable "mbm_event" monitoring mode:
> + ::
> +
> + # echo "mbm_event" > /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 maximum number of counter IDs (total of available and assigned counters)
> in each domain when the system supports mbm_event mode.
> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
> index 14d99c723ea5..adc9ff3efdfd 100644
> --- a/fs/resctrl/internal.h
> +++ b/fs/resctrl/internal.h
> @@ -414,6 +414,8 @@ void resctrl_unassign_cntr_event(struct rdt_resource *r, struct rdt_mon_domain *
> struct rdtgroup *rdtgrp, struct mon_evt *mevt);
> int mbm_cntr_get(struct rdt_resource *r, struct rdt_mon_domain *d,
> struct rdtgroup *rdtgrp, enum resctrl_event_id evtid);
> +void resctrl_reset_rmid_all(struct rdt_resource *r, struct rdt_mon_domain *d);
> +void mbm_cntr_free_all(struct rdt_resource *r, struct rdt_mon_domain *d);
>
> #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
> int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index 618c94cd1ad8..504b869570e6 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -1045,6 +1045,33 @@ static void mbm_cntr_free(struct rdt_mon_domain *d, int cntr_id)
> memset(&d->cntr_cfg[cntr_id], 0, sizeof(struct mbm_cntr_cfg));
> }
>
> +/**
> + * mbm_cntr_free_all() - Clear all the counter ID configuration details in the
> + * domain @d. Called when mbm_assign_mode is changed.
> + */
> +void mbm_cntr_free_all(struct rdt_resource *r, struct rdt_mon_domain *d)
> +{
> + memset(d->cntr_cfg, 0, sizeof(*d->cntr_cfg) * r->mon.num_mbm_cntrs);
> +}
> +
> +/**
> + * resctrl_reset_rmid_all() - Reset all non-architecture states for all the
> + * supported RMIDs.
> + */
> +void resctrl_reset_rmid_all(struct rdt_resource *r, struct rdt_mon_domain *d)
struct rdt_resource *r is unused? At this time it seems unnecessary to check if
an MBM event belongs to particular resource since at this point I expect only L3
is possible. Even so, to be consistent and robust I think it would make flows
easier to understand by always ensureing that mon_evt::rid matches
expected resource.
> +{
> + u32 idx_limit = resctrl_arch_system_num_rmid_idx();
> + enum resctrl_event_id evt;
> + int idx;
> +
> + for_each_mbm_event_id(evt) {
> + if (!resctrl_is_mon_event_enabled(evt))
> + continue;
> + idx = MBM_STATE_IDX(evt);
> + memset(d->mbm_states[idx], 0, sizeof(struct mbm_state) * idx_limit);
sizeof(*d->mbm_states[0])?
> + }
> +}
> +
> /**
> * resctrl_alloc_config_cntr() - Allocate a counter ID and configure it for the
> * event pointed to by @mevt and the resctrl group @rdtgrp within the domain @d.
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index 8c67e0897f25..6bb61fcf8673 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -1876,6 +1876,77 @@ static int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of,
> return 0;
> }
>
> +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 = rdt_kn_parent_priv(of->kn);
> + struct rdt_mon_domain *d;
> + 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_event")) {
> + if (r->mon.mbm_cntr_assignable) {
> + enable = 1;
> + } else {
> + ret = -EINVAL;
> + rdt_last_cmd_puts("mbm_event mode is not supported\n");
> + goto write_exit;
write_exit -> out_unlock
> + }
> + } 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)
> + goto write_exit;
> +
> + /* Update the visibility of BMEC related files */
> + resctrl_bmec_files_show(r, !enable);
> +
> + /*
> + * Initialize the default memory transaction values for
> + * total and local events.
> + */
> + if (resctrl_is_mon_event_enabled(QOS_L3_MBM_TOTAL_EVENT_ID))
> + resctrl_set_mon_evt_cfg(QOS_L3_MBM_TOTAL_EVENT_ID,
> + MAX_EVT_CONFIG_BITS);
> + if (resctrl_is_mon_event_enabled(QOS_L3_MBM_LOCAL_EVENT_ID))
> + resctrl_set_mon_evt_cfg(QOS_L3_MBM_LOCAL_EVENT_ID,
> + READS_TO_LOCAL_MEM |
> + READS_TO_LOCAL_S_MEM |
> + NON_TEMP_WRITE_TO_LOCAL_MEM);
Nice, yes, this belongs in resctrl fs.
> + /*
> + * Reset all the non-achitectural RMID state and assignable counters.
> + */
> + list_for_each_entry(d, &r->mon_domains, hdr.list) {
> + mbm_cntr_free_all(r, d);
> + resctrl_reset_rmid_all(r, d);
> + }
> + }
> +
> +write_exit:
> + mutex_unlock(&rdtgroup_mutex);
> + cpus_read_unlock();
> +
> + return ret ?: nbytes;
> +}
> +
> static int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of,
> struct seq_file *s, void *v)
> {
> @@ -2203,8 +2274,8 @@ static int resctrl_process_assign(struct rdt_resource *r, struct rdtgroup *rdtgr
> struct mon_evt *mevt;
> int assign_state;
> char domain[10];
> + int ret = 0;
> bool found;
> - int ret;
>
> mevt = mbm_get_mon_event_by_name(r, event);
> if (!mevt) {
> @@ -2249,7 +2320,7 @@ static int resctrl_process_assign(struct rdt_resource *r, struct rdtgroup *rdtgr
>
> switch (assign_state) {
> case ASSIGN_NONE:
> - ret = resctrl_unassign_cntr_event(r, d, rdtgrp, mevt);
> + resctrl_unassign_cntr_event(r, d, rdtgrp, mevt);
> break;
> case ASSIGN_EXCLUSIVE:
> ret = resctrl_assign_cntr_event(r, d, rdtgrp, mevt);
Two stray hunks?
> @@ -2463,9 +2534,10 @@ 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 | RFTYPE_RES_CACHE,
> },
> {
Reinette
