linux-kernel - Re: [PATCH v12 20/26] x86/resctrl: Provide interface to update the event configurations

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Message-ID: <7423145d-7de7-4414-85be-b7325c01b437@amd.com>
Date: Tue, 15 Apr 2025 15:37:40 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, tony.luck@...el.com,
 peternewman@...gle.com
Cc: corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
 paulmck@...nel.org, akpm@...ux-foundation.org, thuth@...hat.com,
 rostedt@...dmis.org, ardb@...nel.org, gregkh@...uxfoundation.org,
 daniel.sneddon@...ux.intel.com, jpoimboe@...nel.org,
 alexandre.chartre@...cle.com, pawan.kumar.gupta@...ux.intel.com,
 thomas.lendacky@....com, perry.yuan@....com, seanjc@...gle.com,
 kai.huang@...el.com, xiaoyao.li@...el.com, kan.liang@...ux.intel.com,
 xin3.li@...el.com, ebiggers@...gle.com, xin@...or.com,
 sohil.mehta@...el.com, andrew.cooper3@...rix.com, mario.limonciello@....com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 maciej.wieczor-retman@...el.com, eranian@...gle.com
Subject: Re: [PATCH v12 20/26] x86/resctrl: Provide interface to update the
 event configurations

Hi Reinette,

On 4/11/25 17:07, Reinette Chatre wrote:
> Hi Babu,
> 
> On 4/3/25 5:18 PM, Babu Moger wrote:
>> Users can modify the event configuration by writing to the event_filter
>> interface file. The event configurations for mbm_cntr_assign mode are
>> located in /sys/fs/resctrl/info/event_configs/.
>>
>> Update the assignments of all groups when the event configuration is
>> modified.
>>
>> Example:
>> $ cd /sys/fs/resctrl/
>> $ echo "local_reads, local_non_temporal_writes" >
>>   info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>>
>> $ cat info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>>  local_reads, local_non_temporal_writes
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> v12: New patch to modify event configurations.
>> ---
>>  Documentation/arch/x86/resctrl.rst     |  10 +++
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 115 ++++++++++++++++++++++++-
>>  2 files changed, 124 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
>> index 99f9f4b9b501..4e6feba6fb08 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -335,6 +335,16 @@ with the following files:
>>  	    # cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes/event_filter
>>  	    local_reads, local_non_temporal_writes, local_reads_slow_memory
>>  
>> +	The event configuration can be modified by writing to the event_filter file within
>> +	the configuration directory.
> 
> Please use imperative tone.

Sure.

Basic question - Should the user doc also be in imperative mode? I thought
it only applies to commit log.

> 
>> +	::
>> +
>> +	    # echo "local_reads, local_non_temporal_writes" >
>> +	      /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>> +
>> +	    # cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>> +	    local_reads, local_non_temporal_writes
>> +
>>  "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/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index b2122a1dd36c..7792455f0b26 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -1926,6 +1926,118 @@ static int event_filter_show(struct kernfs_open_file *of, struct seq_file *seq,
>>  	return 0;
>>  }
>>  
> 
> Could you please add comments to these new functions to explain what they do?

Sure.

> 
>> +static int resctrl_group_assign(struct rdt_resource *r, struct rdtgroup *rdtgrp,
>> +				enum resctrl_event_id evtid, u32 evt_cfg)
>> +{
>> +	struct rdt_mon_domain *d;
>> +	int cntr_id, ret;
>> +
>> +	list_for_each_entry(d, &r->mon_domains, hdr.list) {
>> +		cntr_id = mbm_cntr_get(r, d, rdtgrp, evtid);
>> +		if (cntr_id >= 0 && d->cntr_cfg[cntr_id].evt_cfg != evt_cfg) {
>> +			d->cntr_cfg[cntr_id].evt_cfg = evt_cfg;
>> +			ret = resctrl_arch_config_cntr(r, d, evtid, rdtgrp->mon.rmid,
>> +						       rdtgrp->closid, cntr_id, evt_cfg, true);
>> +			if (ret) {
>> +				rdt_last_cmd_printf("Assign failed event %d domain %d group %s\n",
>> +						    evtid, d->hdr.id, rdtgrp->kn->name);
> 
> Please provide the actual event name to user space. The event IDs are not visible to
> user space.

Sure.

-- 
Thanks
Babu Moger