Message-ID: <d0123331-49e0-4948-991d-ea908785bff7@intel.com>
Date: Wed, 25 Jun 2025 16:23:51 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
	<Dave.Martin@....com>, <james.morse@....com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
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Subject: Re: [PATCH v14 24/32] fs/resctrl: Add event configuration directory
 under info/L3_MON/

Hi Babu,

On 6/13/25 2:05 PM, Babu Moger wrote:
> When assignable counters are supported the
> /sys/fs/resctrl/info/L3_MON/event_configs directory contains a
> sub-directory for each MBM event that can be assigned to a counter.
> The MBM event sub-directory contains a file named "event_filter" that
> is used to view and modify which memory transactions the MBM event is
> configured with.
> 
> Create the /sys/fs/resctrl/info/L3_MON/event_configs directory on resctrl
> mount and pre-populate it with directories for the two existing MBM events:
> mbm_total_bytes and mbm_local_bytes. Create the "event_filter" file within
> each MBM event directory with the needed *show() that displays the memory
> transactions with which the MBM event is configured.
> 
> Example:
> $ mount -t resctrl resctrl /sys/fs/resctrl
> $ cd /sys/fs/resctrl/
> $ cat info/L3_MON/event_configs/mbm_total_bytes/event_filter
>   local_reads, remote_reads, local_non_temporal_writes,
>   remote_non_temporal_writes, local_reads_slow_memory,
>   remote_reads_slow_memory, dirty_victim_writes_all
> 
> $ cat info/L3_MON/event_configs/mbm_local_bytes/event_filter
>   local_reads, local_non_temporal_writes, local_reads_slow_memory

Please let these examples match what the patch does wrt spacing.

> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---

...

> ---
>  Documentation/filesystems/resctrl.rst | 32 +++++++++++
>  fs/resctrl/internal.h                 |  2 +
>  fs/resctrl/monitor.c                  |  1 +
>  fs/resctrl/rdtgroup.c                 | 78 +++++++++++++++++++++++++++
>  4 files changed, 113 insertions(+)
> 
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 18de335e1ff8..b1db1a53db2a 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -310,6 +310,38 @@ with the following files:
>  	  # cat /sys/fs/resctrl/info/L3_MON/available_mbm_cntrs
>  	  0=30;1=30
>  
> +"event_configs":
> +	Directory that exists when "mbm_event" mode is supported. Contains

""mbm_event" mode" -> ""mbm_event" counter assignment mode"

> +	sub-directory for each MBM event that can be assigned to a counter.
> +
> +	Two MBM events are supported by default: mbm_local_bytes and mbm_total_bytes.
> +	Each MBM event's sub-directory contains a file named "event_filter" that is
> +	used to view and modify which memory transactions the MBM event is configured
> +	with.
> +
> +	List of memory transaction types supported:
> +
> +	==========================  ========================================================
> +	Name			    Description
> +	==========================  ========================================================
> +	dirty_victim_writes_all     Dirty Victims from the QOS domain to all types of memory
> +	remote_reads_slow_memory    Reads to slow memory in the non-local NUMA domain
> +	local_reads_slow_memory     Reads to slow memory in the local NUMA domain
> +	remote_non_temporal_writes  Non-temporal writes to non-local NUMA domain
> +	local_non_temporal_writes   Non-temporal writes to local NUMA domain
> +	remote_reads                Reads to memory in the non-local NUMA domain
> +	local_reads                 Reads to memory in the local NUMA domain
> +	==========================  ========================================================
> +
> +	For example::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_total_bytes/event_filter
> +	  local_reads, remote_reads, local_non_temporal_writes, remote_non_temporal_writes,
> +	  local_reads_slow_memory, remote_reads_slow_memory, dirty_victim_writes_all
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_local_bytes/event_filter
> +	  local_reads, local_non_temporal_writes, local_reads_slow_memory
> +

Please let these examples match what the patch does wrt spacing.

>  "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 84a136194d9a..ed0e3b695ad5 100644
> --- a/fs/resctrl/internal.h
> +++ b/fs/resctrl/internal.h
> @@ -248,6 +248,8 @@ struct mbm_config_value {
>  
>  #define RFTYPE_DEBUG			BIT(10)
>  
> +#define RFTYPE_ASSIGN_CONFIG		BIT(11)
> +
>  #define RFTYPE_CTRL_INFO		(RFTYPE_INFO | RFTYPE_CTRL)
>  
>  #define RFTYPE_MON_INFO			(RFTYPE_INFO | RFTYPE_MON)
> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index ef6ef58f180b..09a49029a800 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -956,6 +956,7 @@ int resctrl_mon_resource_init(void)
>  					 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
>  		resctrl_file_fflags_init("available_mbm_cntrs",
>  					 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
> +		resctrl_file_fflags_init("event_filter", RFTYPE_ASSIGN_CONFIG);
>  	}
>  
>  	return 0;
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index 5fb6a9939e23..e2fa5e10c2dd 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -1909,6 +1909,25 @@ static int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of,
>  	return ret;
>  }
>  
> +static int event_filter_show(struct kernfs_open_file *of, struct seq_file *seq, void *v)
> +{
> +	struct mon_evt *mevt = rdt_kn_parent_priv(of->kn);
> +	bool sep = false;
> +	int i;
> +
> +	for (i = 0; i < NUM_MBM_EVT_VALUES; i++) {
> +		if (mevt->evt_cfg & mbm_config_values[i].val) {
> +			if (sep)
> +				seq_putc(seq, ',');
> +			seq_printf(seq, "%s", mbm_config_values[i].name);

Taking a closer look I think we need to be more careful about how the
code is organized. Ideally the monitoring related code and data should
be located in fs/resctrl/monitor.c. Having event_filter_show() here is
ok because of its use in res_common_files[]. Since it is monitoring related
I expected its code/data to be in fs/resctrl/monitor.c, thus that
mbm_config_values[] (mbm_transactions[]?) to be in fs/resctrl/monitor.c,
(just like mon_event_all[]).

> +			sep = true;
> +		}
> +	}
> +	seq_putc(seq, '\n');
> +
> +	return 0;
> +}
> +
>  /* rdtgroup information files for one cache resource. */
>  static struct rftype res_common_files[] = {
>  	{
> @@ -2033,6 +2052,12 @@ static struct rftype res_common_files[] = {
>  		.seq_show	= mbm_local_bytes_config_show,
>  		.write		= mbm_local_bytes_config_write,
>  	},
> +	{
> +		.name		= "event_filter",
> +		.mode		= 0444,
> +		.kf_ops		= &rdtgroup_kf_single_ops,
> +		.seq_show	= event_filter_show,
> +	},
>  	{
>  		.name		= "mbm_assign_mode",
>  		.mode		= 0444,
> @@ -2315,6 +2340,53 @@ static int rdtgroup_mkdir_info_resdir(void *priv, char *name,
>  	return ret;
>  }
>  
> +static int resctrl_mkdir_counter_configs(struct rdt_resource *r, char *name)

This can now be named resctrl_mkdir_event_configs()?

Also, I cannot see where the struct rdt_resource parameter is used. It should not
be removed though, as mentioned earlier it should be used to ensure
to check the mon_evt::rid values so that only events associated with resource
are considered.

> +{
> +	struct kernfs_node *l3_mon_kn, *kn_subdir, *kn_subdir2;
> +	struct mon_evt *mevt;
> +	int ret;
> +
> +	l3_mon_kn = kernfs_find_and_get(kn_info, name);
> +	if (!l3_mon_kn)
> +		return -ENOENT;

Needing to figure out this kn does not seem necessary. Can it not be
provided via parameter instead?

For example, resctrl_mkdir_counter_configs() (rather resctrl_mkdir_event_configs())
can be called from rdtgroup_mkdir_info_resdir(). I understand rdtgroup_mkdir_info_resdir()
is also called for  struct resctrl_schema parameter but I think the fflags can be used
to make the right decision. Something like:

	rdtgroup_mkdir_info_resdir() {
		struct rdt_resource *r;

		...
		if (fflags & RFTYPE_MON_INFO) {
			r = priv;
			if (r->mon.mbm_cntr_assignable) {
				ret = resctrl_mkdir_event_configs(kn_subdir, r);
				...
			}
		}
	}

What do you think?		    

> +
> +	kn_subdir = kernfs_create_dir(l3_mon_kn, "event_configs", l3_mon_kn->mode, NULL);
> +	if (IS_ERR(kn_subdir)) {
> +		kernfs_put(l3_mon_kn);
> +		return PTR_ERR(kn_subdir);
> +	}
> +
> +	ret = rdtgroup_kn_set_ugid(kn_subdir);
> +	if (ret) {
> +		kernfs_put(l3_mon_kn);
> +		return ret;
> +	}
> +
> +	for (mevt = &mon_event_all[0]; mevt < &mon_event_all[QOS_NUM_EVENTS]; mevt++) {

Here is a spot where the for_each_mon_event() should be used.

> +		if (!mevt->enabled || !resctrl_is_mbm_event(mevt->evtid))
> +			continue;
> +
> +		kn_subdir2 = kernfs_create_dir(kn_subdir, mevt->name, kn_subdir->mode, mevt);
> +		if (IS_ERR(kn_subdir2)) {
> +			ret = PTR_ERR(kn_subdir2);
> +			goto out_config;
> +		}
> +
> +		ret = rdtgroup_kn_set_ugid(kn_subdir2);
> +		if (ret)
> +			goto out_config;
> +
> +		ret = rdtgroup_add_files(kn_subdir2, RFTYPE_ASSIGN_CONFIG);
> +		if (!ret)
> +			kernfs_activate(kn_subdir);
> +	}
> +
> +out_config:
> +	kernfs_put(l3_mon_kn);
> +
> +	return ret;
> +}
> +
>  static unsigned long fflags_from_resource(struct rdt_resource *r)
>  {
>  	switch (r->rid) {
> @@ -2361,6 +2433,12 @@ static int rdtgroup_create_info_dir(struct kernfs_node *parent_kn)
>  		ret = rdtgroup_mkdir_info_resdir(r, name, fflags);
>  		if (ret)
>  			goto out_destroy;
> +
> +		if (r->mon.mbm_cntr_assignable) {
> +			ret = resctrl_mkdir_counter_configs(r, name);
> +			if (ret)
> +				goto out_destroy;
> +		}
>  	}
>  
>  	ret = rdtgroup_kn_set_ugid(kn_info);


Reinette

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