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Message-ID: <4b3e158b-2e27-409d-8b23-8fa042939132@amd.com>
Date: Wed, 6 Aug 2025 16:12:11 -0500
From: "Moger, Babu" <babu.moger@....com>
To: corbet@....net, tony.luck@...el.com, reinette.chatre@...el.com,
james.morse@....com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com
Cc: Dave.Martin@....com, x86@...nel.org, hpa@...or.com,
akpm@...ux-foundation.org, paulmck@...nel.org, rostedt@...dmis.org,
Neeraj.Upadhyay@....com, david@...hat.com, arnd@...db.de, fvdl@...gle.com,
seanjc@...gle.com, jpoimboe@...nel.org, pawan.kumar.gupta@...ux.intel.com,
xin@...or.com, manali.shukla@....com, tao1.su@...ux.intel.com,
sohil.mehta@...el.com, kai.huang@...el.com, xiaoyao.li@...el.com,
peterz@...radead.org, xin3.li@...el.com, kan.liang@...ux.intel.com,
mario.limonciello@....com, thomas.lendacky@....com, perry.yuan@....com,
gautham.shenoy@....com, chang.seok.bae@...el.com, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, peternewman@...gle.com, eranian@...gle.com
Subject: Re: [PATCH v16 11/34] fs/resctrl: Add resctrl file to display number
of assignable counters
Hi Reinette,
On 7/25/25 13:29, Babu Moger wrote:
> The "mbm_event" counter assignment mode allows users to assign a hardware
> counter to an RMID, event pair and monitor bandwidth usage as long as it is
> assigned. The hardware continues to track the assigned counter until it is
> explicitly unassigned by the user.
>
> Create 'num_mbm_cntrs' resctrl file that displays the number of counters
> supported in each domain. 'num_mbm_cntrs' is only visible to user space
> when the system supports "mbm_event" mode.
>
> Signed-off-by: Babu Moger <babu.moger@....com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> ---
> v16: Added Reviewed-by tag.
>
> v15: Changed "assign a hardware counter ID" to "assign a hardware counter"
> in couple of places.
>
> v14: Minor update to changelog and user doc (resctrl.rst).
> Changed subject line to fs/resctrl.
>
> v13: Updated the changelog.
> Added fflags RFTYPE_RES_CACHE to the file num_mbm_cntrs.
> Replaced seq_puts from seq_putc where applicable.
> Resolved conflicts caused by the recent FS/ARCH code restructure.
> The files monitor.c/rdtgroup.c have been split between FS and ARCH directories.
>
> v12: Changed the code to display the max supported monitoring counters in
> each domain. Also updated the documentation.
> Resolved the conflict with the latest code.
>
> v11: Renamed rdtgroup_num_mbm_cntrs_show() to resctrl_num_mbm_cntrs_show().
> Few monor text updates.
>
> v10: No changes.
>
> v9: Updated user document based on the comments.
> Will add a new file available_mbm_cntrs later in the series.
>
> v8: Commit message update and documentation update.
>
> v7: Minor commit log text changes.
>
> v6: No changes.
>
> v5: Changed the display name from num_cntrs to num_mbm_cntrs.
> Updated the commit message.
> Moved the patch after mbm_mode is introduced.
>
> v4: Changed the counter name to num_cntrs. And few text changes.
>
> v3: Changed the field name to mbm_assign_cntrs.
>
> v2: Changed the field name to mbm_assignable_counters from abmc_counter.
> ---
> Documentation/filesystems/resctrl.rst | 11 ++++++++++
> fs/resctrl/monitor.c | 2 ++
> fs/resctrl/rdtgroup.c | 30 +++++++++++++++++++++++++++
> 3 files changed, 43 insertions(+)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index b692829fec5f..4eb27530be6f 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -288,6 +288,17 @@ with the following files:
> result in misleading values or display "Unavailable" if no counter is assigned
> to the event.
>
> +"num_mbm_cntrs":
> + The maximum number of counters (total of available and assigned counters) in
> + each domain when the system supports mbm_event mode.
> +
> + For example, on a system with maximum of 32 memory bandwidth monitoring
> + counters in each of its L3 domains:
> + ::
> +
> + # cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
> + 0=32;1=32
> +
> "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 66c8c635f4b3..4539b08db7b9 100644
> --- a/fs/resctrl/monitor.c
> +++ b/fs/resctrl/monitor.c
> @@ -929,6 +929,8 @@ int resctrl_mon_resource_init(void)
> resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID);
> if (!resctrl_is_mon_event_enabled(QOS_L3_MBM_LOCAL_EVENT_ID))
> resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID);
> + resctrl_file_fflags_init("num_mbm_cntrs",
> + RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
> }
>
> return 0;
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index c7ca9113a12a..acbda73a9b9d 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -1829,6 +1829,30 @@ static int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of,
> return 0;
> }
>
> +static int resctrl_num_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;
> +
> + cpus_read_lock();
> + mutex_lock(&rdtgroup_mutex);
> +
> + list_for_each_entry(dom, &r->mon_domains, hdr.list) {
> + if (sep)
> + seq_putc(s, ';');
> +
> + seq_printf(s, "%d=%d", dom->hdr.id, r->mon.num_mbm_cntrs);
> + sep = true;
> + }
> + seq_putc(s, '\n');
> +
> + mutex_unlock(&rdtgroup_mutex);
> + cpus_read_unlock();
> + return 0;
> +}
How about moving this also to monitor.c?
> /* rdtgroup information files for one cache resource. */
> static struct rftype res_common_files[] = {
> {
> @@ -1866,6 +1890,12 @@ static struct rftype res_common_files[] = {
> .seq_show = rdt_default_ctrl_show,
> .fflags = RFTYPE_CTRL_INFO | RFTYPE_RES_CACHE,
> },
> + {
> + .name = "num_mbm_cntrs",
> + .mode = 0444,
> + .kf_ops = &rdtgroup_kf_single_ops,
> + .seq_show = resctrl_num_mbm_cntrs_show,
> + },
> {
> .name = "min_cbm_bits",
> .mode = 0444,
--
Thanks
Babu Moger
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