linux-kernel - Re: [PATCH v14 14/32] fs/resctrl: Introduce interface to display number of free MBM counters

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Message-ID: <3915f9cd-5c82-4947-b5c6-47b5ecdef5c2@amd.com>
Date: Thu, 26 Jun 2025 09:17:45 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.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
Cc: x86@...nel.org, hpa@...or.com, akpm@...ux-foundation.org,
 rostedt@...dmis.org, paulmck@...nel.org, thuth@...hat.com, ardb@...nel.org,
 gregkh@...uxfoundation.org, seanjc@...gle.com, thomas.lendacky@....com,
 pawan.kumar.gupta@...ux.intel.com, manali.shukla@....com,
 perry.yuan@....com, kai.huang@...el.com, peterz@...radead.org,
 xiaoyao.li@...el.com, kan.liang@...ux.intel.com, mario.limonciello@....com,
 xin3.li@...el.com, gautham.shenoy@....com, xin@...or.com,
 chang.seok.bae@...el.com, fenghuay@...dia.com, peternewman@...gle.com,
 maciej.wieczor-retman@...el.com, eranian@...gle.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v14 14/32] fs/resctrl: Introduce interface to display
 number of free MBM counters

Hi Reinette

On 6/24/25 18:39, Reinette Chatre wrote:
> Hi Babu,
> 
> On 6/13/25 2:04 PM, Babu Moger wrote:
>> Provide the interface to display the number of counters IDs available for
> 
> "Introduce the "available_mbm_cntrs" resctrl file to display the number of
> counters available ..."

Sure.

> ,
>> assignment in each domain when "mbm_event" mode is enabled.
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
> ...
> 
>> ---
>>  Documentation/filesystems/resctrl.rst | 11 ++++++
>>  fs/resctrl/monitor.c                  |  5 ++-
>>  fs/resctrl/rdtgroup.c                 | 48 +++++++++++++++++++++++++++
>>  3 files changed, 63 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
>> index 801914de0c81..8a2050098091 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 assignable counters available in each domain when
> 
> "The number of counters available for assignment in each domain ..."

Sure.
> 
>> +	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 92a87aa97b0f..2893da994f3c 100644
>> --- a/fs/resctrl/monitor.c
>> +++ b/fs/resctrl/monitor.c
>> @@ -924,9 +924,12 @@ int resctrl_mon_resource_init(void)
>>  	else if (resctrl_is_mon_event_enabled(QOS_L3_MBM_TOTAL_EVENT_ID))
>>  		mba_mbps_default_event = QOS_L3_MBM_TOTAL_EVENT_ID;
>>  
>> -	if (r->mon.mbm_cntr_assignable)
>> +	if (r->mon.mbm_cntr_assignable) {
>>  		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 90b52593ef29..08bcca9bd8b6 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_cntr_assign mode is not enabled\n");
>> +		ret = -EINVAL;
>> +		goto unlock_cntrs_show;
> 
> unlock_cntrs_show -> out_unlock (to be consistent with rest of resctrl)
> 

Sure.
-- 
Thanks
Babu Moger