linux-kernel - Re: [PATCH v10 09/24] x86/resctrl: Introduce interface to display number of monitoring counters

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Message-ID: <ee8c0576-7609-4f57-97a3-303adcf49faa@amd.com>
Date: Fri, 20 Dec 2024 09:41:29 -0600
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
 Babu Moger <babu.moger@....com>, corbet@....net, tglx@...utronix.de,
 mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
 tony.luck@...el.com, peternewman@...gle.com
Cc: fenghua.yu@...el.com, x86@...nel.org, hpa@...or.com, paulmck@...nel.org,
 akpm@...ux-foundation.org, thuth@...hat.com, rostedt@...dmis.org,
 xiongwei.song@...driver.com, pawan.kumar.gupta@...ux.intel.com,
 daniel.sneddon@...ux.intel.com, jpoimboe@...nel.org, perry.yuan@....com,
 kai.huang@...el.com, xiaoyao.li@...el.com, seanjc@...gle.com,
 xin3.li@...el.com, andrew.cooper3@...rix.com, ebiggers@...gle.com,
 mario.limonciello@....com, james.morse@....com, tan.shaopeng@...itsu.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 maciej.wieczor-retman@...el.com, eranian@...gle.com
Subject: Re: [PATCH v10 09/24] x86/resctrl: Introduce interface to display
 number of monitoring counters

Hi Reinette,

On 12/19/2024 4:03 PM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 12/12/24 12:15 PM, Babu Moger wrote:
>> The mbm_cntr_assign mode provides an option to the user to assign a
>> counter to an RMID, event pair and monitor the bandwidth as long as
>> the counter is assigned. Number of assignments depend on number of
>> monitoring counters available.
>>
>> Provide the interface to display the number of monitoring counters
>> supported. The interface file 'num_mbm_cntrs' is available when an
>> architecture supports mbm_cntr_assign mode.
> 
> How about: "The resctrl file 'num_mbm_cntrs' is visible to user space
> when the system supports mbm_cntr_assign mode." ?

Sure.

> 
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> 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/arch/x86/resctrl.rst     | 12 ++++++++++++
>>   arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 ++++++++++++++++
>>   3 files changed, 29 insertions(+)
>>
>> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
>> index 1e4a1f615496..43a861adeada 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -290,6 +290,18 @@ with the following files:
>>   	"mbm_total_bytes" or "mbm_local_bytes" will report 'Unavailable' if
>>   	there is no counter associated with that event.
>>   
>> +"num_mbm_cntrs":
>> +	The number of monitoring counters available for assignment when the
>> +	architecture supports mbm_cntr_assign mode.
> 
> "architecture supports" -> "system supports"

Sure.

> 
>> +
>> +	The resctrl file system supports tracking up to two memory bandwidth
>> +	events per monitoring group: mbm_total_bytes and/or mbm_local_bytes.
>> +	Up to two counters can be assigned per monitoring group, one for each
>> +	memory bandwidth event. More monitoring groups can be tracked by
>> +	assigning one counter per monitoring group. However, doing so limits
>> +	memory bandwidth tracking to a single memory bandwidth event per
>> +	monitoring group.
>> +
>>   "max_threshold_occupancy":
>>   		Read/write file provides the largest value (in
>>   		bytes) at which a previously used LLC_occupancy
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index 80be91671dc1..c23e94fa6852 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -1237,6 +1237,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
>>   			r->mon.mbm_cntr_assignable = true;
>>   			cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx);
>>   			r->mon.num_mbm_cntrs = (ebx & GENMASK(15, 0)) + 1;
>> +			resctrl_file_fflags_init("num_mbm_cntrs", RFTYPE_MON_INFO);
>>   		}
>>   	}
>>   
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index f25ff1430014..339bb0b09a82 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -869,6 +869,16 @@ static int rdtgroup_mbm_assign_mode_show(struct kernfs_open_file *of,
>>   	return 0;
>>   }
>>   
>> +static int rdtgroup_num_mbm_cntrs_show(struct kernfs_open_file *of,
>> +				       struct seq_file *s, void *v)
> 
> No rdtgroup_ namespace, this can be resctrl_

Yes. Sure.

thanks
Babu
> 
>> +{
>> +	struct rdt_resource *r = of->kn->parent->priv;
>> +
>> +	seq_printf(s, "%d\n", r->mon.num_mbm_cntrs);
>> +
>> +	return 0;
>> +}
>> +
>>   #ifdef CONFIG_PROC_CPU_RESCTRL
>>   
>>   /*
> 
> Reinette
> 
>