linux-kernel - Re: [PATCH v10 13/24] x86/resctrl: Introduce interface to display number of free counters

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Message-ID: <ed9544cf-c4e3-4f67-8f52-aa78e516fe5e@amd.com>
Date: Fri, 20 Dec 2024 12:32:08 -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,
 sandipan.das@....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 13/24] x86/resctrl: Introduce interface to display
 number of free counters

Hi Reinette,

On 12/19/2024 4:50 PM, Reinette Chatre wrote:
> (andipan.das@....com -> sandipan.das@....com to stop sending undeliverable emails)
> 
> Hi Babu,
> 
> On 12/12/24 12:15 PM, Babu Moger wrote:
>> Provide the interface to display the number of monitoring counters
>> available for assignment in each domain when mbm_cntr_assign is supported.
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> 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/arch/x86/resctrl.rst     |  4 +++
>>   arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 47 ++++++++++++++++++++++++++
>>   3 files changed, 52 insertions(+)
>>
>> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
>> index 43a861adeada..c075fcee96b7 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -302,6 +302,10 @@ with the following files:
>>   	memory bandwidth tracking to a single memory bandwidth event per
>>   	monitoring group.
>>   
>> +"available_mbm_cntrs":
>> +	The number of monitoring counters available for assignment in each
>> +	domain when the architecture supports mbm_cntr_assign mode.
> 
> "architecture supports" -> "system supports"
> 
> It looks to me as though more than just support is required, the mode
> is also required to be enabled?

Yes. It needs to be enabled.

The number of monitoring counters available for assignment in each
domain when mbm_cntr_assign mode is enabled on the system.

> 
>> +
>>   "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 b07d60fabf1c..f857af361af1 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -1238,6 +1238,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
>>   			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);
>> +			resctrl_file_fflags_init("available_mbm_cntrs", RFTYPE_MON_INFO);
>>   		}
>>   	}
>>   
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 1ee008a63d8b..72518e0ec2ec 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -879,6 +879,47 @@ static int rdtgroup_num_mbm_cntrs_show(struct kernfs_open_file *of,
>>   	return 0;
>>   }
>>   
>> +static int rdtgroup_available_mbm_cntrs_show(struct kernfs_open_file *of,
>> +					     struct seq_file *s, void *v)
> 
> rdtgroup_
> 
>> +{
>> +	struct rdt_resource *r = of->kn->parent->priv;
>> +	struct rdt_mon_domain *dom;
>> +	bool sep = false;
>> +	u32 cntrs, i;
>> +	int ret = 0;
>> +
>> +	cpus_read_lock();
>> +	mutex_lock(&rdtgroup_mutex);
>> +
>> +	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;
>> +	}
>> +
>> +
> 
> unnecessary empty line
> 
>> +	list_for_each_entry(dom, &r->mon_domains, hdr.list) {
>> +		if (sep)
>> +			seq_puts(s, ";");
>> +
>> +		cntrs = 0;
>> +		for (i = 0; i < r->mon.num_mbm_cntrs; i++) {
>> +			if (!dom->cntr_cfg[i].rdtgrp)
>> +				cntrs++;
>> +		}
>> +
>> +		seq_printf(s, "%d=%d", dom->hdr.id, cntrs);
>> +		sep = true;
>> +	}
>> +	seq_puts(s, "\n");
>> +
>> +unlock_cntrs_show:
>> +	mutex_unlock(&rdtgroup_mutex);
>> +	cpus_read_unlock();
>> +
>> +	return ret;
>> +}
>> +
>>   #ifdef CONFIG_PROC_CPU_RESCTRL
>>   
>>   /*
>> @@ -1961,6 +2002,12 @@ static struct rftype res_common_files[] = {
>>   		.kf_ops		= &rdtgroup_kf_single_ops,
>>   		.seq_show	= rdtgroup_num_mbm_cntrs_show,
>>   	},
>> +	{
>> +		.name		= "available_mbm_cntrs",
>> +		.mode		= 0444,
>> +		.kf_ops		= &rdtgroup_kf_single_ops,
>> +		.seq_show	= rdtgroup_available_mbm_cntrs_show,
>> +	},
>>   	{
>>   		.name		= "cpus_list",
>>   		.mode		= 0644,
> 
> Reinette
> 
>