Re: [PATCH v15 27/34] fs/resctrl: Provide interface to update the event configurations

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Babu,

On 7/8/25 3:17 PM, Babu Moger wrote:
> When "mbm_event" counter assignment mode is supported, users can modify
> the event configuration by writing to the 'event_filter' resctrl file.
> The event configurations for mbm_event mode are located in
> /sys/fs/resctrl/info/L3_MON/event_configs/.
> 
> Update the assignments of all CTRL_MON and MON resource groups when the
> event configuration is modified.
> 
> Example:
> $ mount -t resctrl resctrl /sys/fs/resctrl
> 
> $ cd /sys/fs/resctrl/
> 
> $ cat info/L3_MON/event_configs/mbm_local_bytes/event_filter
>   local_reads,local_non_temporal_writes,local_reads_slow_memory
> 
> $ echo "local_reads,local_non_temporal_writes" >
>   info/L3_MON/event_configs/mbm_total_bytes/event_filter
> 
> $ cat info/L3_MON/event_configs/mbm_total_bytes/event_filter
>   local_reads,local_non_temporal_writes
> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---

...

> ---
>  Documentation/filesystems/resctrl.rst | 12 +++++
>  fs/resctrl/internal.h                 |  1 +
>  fs/resctrl/monitor.c                  | 44 ++++++++++++++++
>  fs/resctrl/rdtgroup.c                 | 74 ++++++++++++++++++++++++++-
>  4 files changed, 130 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 57fd12f0aeca..06c8c08d0341 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -342,6 +342,18 @@ with the following files:
>  	  # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_local_bytes/event_filter
>  	  local_reads,local_non_temporal_writes,local_reads_slow_memory
>  
> +	Modify the event configuration by writing to the "event_filter" file within
> +	the "event_configs" directory. The read/write "event_filter" file contains the
> +	configuration of the event that reflects which memory transactions are counted by it.
> +
> +	For example::
> +
> +	  # echo "local_reads, local_non_temporal_writes" >
> +	    /sys/fs/resctrl/info/L3_MON/event_configs/mbm_total_bytes/event_filter
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_total_bytes/event_filter
> +	   local_reads,local_non_temporal_writes
> +
>  "max_threshold_occupancy":
>  		Read/write file provides the largest value (in
>  		bytes) at which a previously used LLC_occupancy
> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
> index b107874407b2..b42890fd937a 100644
> --- a/fs/resctrl/internal.h
> +++ b/fs/resctrl/internal.h
> @@ -409,6 +409,7 @@ void rdtgroup_unassign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdt
>  				  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_update_cntr_allrdtgrp(struct mon_evt *mevt);
>  
>  #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 787dce934903..0722e72f6cb1 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -1173,3 +1173,47 @@ void rdtgroup_unassign_cntr_event(struct rdt_mon_domain *d, struct rdtgroup *rdt
>  		rdtgroup_free_config_cntr(r, d, rdtgrp, mevt->evtid);
>  	}
>  }
> +
> +/*
> + * rdtgroup_update_cntr_event - Update the counter assignments for the event
> + *				in a group.
> + * @r:		Resource to which update needs to be done.
> + * @rdtgrp:	Resctrl group.
> + * @mevt:	MBM monitor event.

@mevt needs update match actual parameter

> + */
> +static void rdtgroup_update_cntr_event(struct rdt_resource *r, struct rdtgroup *rdtgrp,
> +				       enum resctrl_event_id evtid)
> +{
> +	struct rdt_mon_domain *d;
> +	int cntr_id;
> +
> +	list_for_each_entry(d, &r->mon_domains, hdr.list) {
> +		cntr_id = mbm_cntr_get(r, d, rdtgrp, evtid);
> +		if (cntr_id >= 0)
> +			resctrl_arch_config_cntr(r, d, evtid, rdtgrp->mon.rmid,
> +						 rdtgrp->closid, cntr_id, true);
> +	}
> +}
> +
> +/*
> + * resctrl_update_cntr_allrdtgrp - Update the counter assignments for the event
> + *				   for all the groups.
> + * @r:		Resource to which update needs to be done.

@r no longer a parameter

> + * @mevt	MBM Monitor event.
> + */
> +void resctrl_update_cntr_allrdtgrp(struct mon_evt *mevt)
> +{
> +	struct rdt_resource *r = resctrl_arch_get_resource(mevt->rid);
> +	struct rdtgroup *prgrp, *crgrp;
> +
> +	/*
> +	 * Find all the groups where the event is assigned and update
> +	 * the assignment

"update the assignment" -> "update the configuration of existing assignments" ?

> +	 */
> +	list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
> +		rdtgroup_update_cntr_event(r, prgrp, mevt->evtid);
> +
> +		list_for_each_entry(crgrp, &prgrp->mon.crdtgrp_list, mon.crdtgrp_list)
> +			rdtgroup_update_cntr_event(r, crgrp, mevt->evtid);
> +	}
> +}
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index bb28ef7e4600..4889e7556cc7 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -1916,6 +1916,77 @@ static int event_filter_show(struct kernfs_open_file *of, struct seq_file *seq,
>  	return 0;
>  }
>  
> +static int resctrl_process_configs(char *tok, u32 *val)

Please move to monitor.c and give more specific name. Perhaps
resctrl_parse_mem_transactions()? Open to ideas.

> +{
> +	u32 temp_val = 0;
> +	char *evt_str;
> +	bool found;
> +	int i;
> +
> +next_config:
> +	if (!tok || tok[0] == '\0') {
> +		*val = temp_val;
> +		return 0;
> +	}
> +
> +	/* Start processing the strings for each memory transaction type */
> +	evt_str = strim(strsep(&tok, ","));
> +	found = false;
> +	for (i = 0; i < NUM_MBM_TRANSACTIONS; i++) {
> +		if (!strcmp(mbm_transactions[i].name, evt_str)) {
> +			temp_val |= mbm_transactions[i].val;
> +			found = true;
> +			break;
> +		}
> +	}
> +
> +	if (!found) {
> +		rdt_last_cmd_printf("Invalid memory transaction type %s\n", evt_str);
> +		return -EINVAL;
> +	}
> +
> +	goto next_config;
> +}
> +
> +static ssize_t event_filter_write(struct kernfs_open_file *of, char *buf,
> +				  size_t nbytes, loff_t off)
> +{
> +	struct mon_evt *mevt = rdt_kn_parent_priv(of->kn);
> +	struct rdt_resource *r;
> +	u32 evt_cfg = 0;
> +	int ret = 0;
> +
> +	/* 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();
> +
> +	r = resctrl_arch_get_resource(mevt->rid);
> +	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
> +		rdt_last_cmd_puts("mbm_event counter assignment mode is not enabled\n");
> +		ret = -EINVAL;
> +		goto out_unlock;
> +	}
> +
> +	ret = resctrl_process_configs(buf, &evt_cfg);
> +	if (!ret && mevt->evt_cfg != evt_cfg) {
> +		mevt->evt_cfg = evt_cfg;
> +		resctrl_update_cntr_allrdtgrp(mevt);
> +	}
> +
> +out_unlock:
> +	mutex_unlock(&rdtgroup_mutex);
> +	cpus_read_unlock();
> +
> +	return ret ?: nbytes;
> +}
> +
>  /* rdtgroup information files for one cache resource. */
>  static struct rftype res_common_files[] = {
>  	{
> @@ -2042,9 +2113,10 @@ static struct rftype res_common_files[] = {
>  	},
>  	{
>  		.name		= "event_filter",
> -		.mode		= 0444,
> +		.mode		= 0644,
>  		.kf_ops		= &rdtgroup_kf_single_ops,
>  		.seq_show	= event_filter_show,
> +		.write		= event_filter_write,
>  	},
>  	{
>  		.name		= "mbm_assign_mode",

Reinette