Re: [PATCH v16 13/34] fs/resctrl: Introduce interface to display number of free MBM counters

["Moger, Babu" <babu.moger@amd.com>]

Hi Reinette,

On 7/25/25 13:29, Babu Moger wrote:
> Introduce the "available_mbm_cntrs" resctrl file to display the number of
> counters available for assignment in each domain when "mbm_event" mode is
> enabled.
> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> ---
> v16: Added Reviewed-by tag.
> 
> v15: Minor changelog text update.
>      Minor resctrl.rst text update and corrected the error text in
>      resctrl_available_mbm_cntrs_show().
>      Changed the goto label to out_unlock for consistency.
> 
> v14: Minor changelog update.
>      Changed subject line to fs/resctrl.
> 
> v13: Resolved conflicts caused by the recent FS/ARCH code restructure.
>      The files monitor.c and rdtgroup.c file has now been split between
>      the FS and ARCH directories.
> 
> v12: Minor change to change log.
>      Updated the documentation text with an example.
>      Replaced seq_puts(s, ";") with seq_putc(s, ';');
>      Added missing rdt_last_cmd_clear() in resctrl_available_mbm_cntrs_show().
> 
> v11: Rename rdtgroup_available_mbm_cntrs_show() to resctrl_available_mbm_cntrs_show().
>      Few minor text changes.
> 
> v10: Patch changed to handle the counters at domain level.
>      https://lore.kernel.org/lkml/CALPaoCj+zWq1vkHVbXYP0znJbe6Ke3PXPWjtri5AFgD9cQDCUg@mail.gmail.com/
>      So, display logic also changed now.
> 
> v9: New patch
> ---
>  Documentation/filesystems/resctrl.rst | 11 ++++++
>  fs/resctrl/monitor.c                  |  2 ++
>  fs/resctrl/rdtgroup.c                 | 48 +++++++++++++++++++++++++++
>  3 files changed, 61 insertions(+)
> 
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 4eb27530be6f..446736dbd97f 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -299,6 +299,17 @@ with the following files:
>  	  # cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
>  	  0=32;1=32
>  
> +"available_mbm_cntrs":
> +	The number of counters available for assignment in each domain when mbm_event
> +	mode is enabled on the system.
> +
> +	For example, on a system with 30 available [hardware] assignable counters
> +	in each of its L3 domains:
> +	::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/available_mbm_cntrs
> +	  0=30;1=30
> +
>  "max_threshold_occupancy":
>  		Read/write file provides the largest value (in
>  		bytes) at which a previously used LLC_occupancy
> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
> index 4539b08db7b9..a0b0ea45c7b4 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -931,6 +931,8 @@ int resctrl_mon_resource_init(void)
>  			resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID);
>  		resctrl_file_fflags_init("num_mbm_cntrs",
>  					 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
> +		resctrl_file_fflags_init("available_mbm_cntrs",
> +					 RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
>  	}
>  
>  	return 0;
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index a09566720d4f..15d10c346307 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -1853,6 +1853,48 @@ static int resctrl_num_mbm_cntrs_show(struct kernfs_open_file *of,
>  	return 0;
>  }
>  
> +static int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of,
> +					    struct seq_file *s, void *v)
> +{
> +	struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
> +	struct rdt_mon_domain *dom;
> +	bool sep = false;
> +	u32 cntrs, i;
> +	int ret = 0;
> +
> +	cpus_read_lock();
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	rdt_last_cmd_clear();
> +
> +	if (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
> +		rdt_last_cmd_puts("mbm_event mode is not enabled\n");
> +		ret = -EINVAL;
> +		goto out_unlock;
> +	}
> +
> +	list_for_each_entry(dom, &r->mon_domains, hdr.list) {
> +		if (sep)
> +			seq_putc(s, ';');
> +
> +		cntrs = 0;
> +		for (i = 0; i < r->mon.num_mbm_cntrs; i++) {
> +			if (!dom->cntr_cfg[i].rdtgrp)
> +				cntrs++;
> +		}
> +
> +		seq_printf(s, "%d=%u", dom->hdr.id, cntrs);
> +		sep = true;
> +	}
> +	seq_putc(s, '\n');
> +
> +out_unlock:
> +	mutex_unlock(&rdtgroup_mutex);
> +	cpus_read_unlock();
> +
> +	return ret;
> +}
> +

This also can be moved to monitor.c.  What do you think?


>  /* rdtgroup information files for one cache resource. */
>  static struct rftype res_common_files[] = {
>  	{
> @@ -1876,6 +1918,12 @@ static struct rftype res_common_files[] = {
>  		.seq_show	= rdt_mon_features_show,
>  		.fflags		= RFTYPE_MON_INFO,
>  	},
> +	{
> +		.name		= "available_mbm_cntrs",
> +		.mode		= 0444,
> +		.kf_ops		= &rdtgroup_kf_single_ops,
> +		.seq_show	= resctrl_available_mbm_cntrs_show,
> +	},
>  	{
>  		.name		= "num_rmids",
>  		.mode		= 0444,

-- 
Thanks
Babu Moger