linux-kernel - Re: [PATCH v15 26/34] fs/resctrl: Add event configuration directory under info/L3

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Message-ID: <0fa9a12b-e900-4ceb-b59c-e653ec3db0ca@intel.com>
Date: Fri, 18 Jul 2025 15:20:22 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...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 v15 26/34] fs/resctrl: Add event configuration directory
 under info/L3_MON/

Hi Babu,

On 7/17/25 8:54 PM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 7/8/25 3:17 PM, Babu Moger wrote:
>> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
>> index 15d10c346307..bb28ef7e4600 100644
>> --- a/fs/resctrl/rdtgroup.c
>> +++ b/fs/resctrl/rdtgroup.c
>> @@ -86,6 +86,8 @@ enum resctrl_event_id mba_mbps_default_event;
>>  
>>  static bool resctrl_debug;
>>  
>> +extern struct mbm_transaction mbm_transactions[NUM_MBM_TRANSACTIONS];
>> +
> 
> Please move this extern to fs/resctrl/internal.h.
> 
>>  void rdt_last_cmd_clear(void)
>>  {
>>  	lockdep_assert_held(&rdtgroup_mutex);
>> @@ -1895,6 +1897,25 @@ static int resctrl_available_mbm_cntrs_show(struct kernfs_open_file *of,
>>  	return ret;
>>  }
>>  
>> +static int event_filter_show(struct kernfs_open_file *of, struct seq_file *seq, void *v)
>> +{
>> +	struct mon_evt *mevt = rdt_kn_parent_priv(of->kn);
>> +	bool sep = false;
>> +	int i;
>> +
>> +	for (i = 0; i < NUM_MBM_TRANSACTIONS; i++) {
>> +		if (mevt->evt_cfg & mbm_transactions[i].val) {
> 
> mevt->evt_cfg could possibly be changed concurrently. This should
> be protected with the rdtgroup_mutex.
> 
>> +			if (sep)
>> +				seq_putc(seq, ',');
>> +			seq_printf(seq, "%s", mbm_transactions[i].name);
>> +			sep = true;
>> +		}
>> +	}
>> +	seq_putc(seq, '\n');
>> +
>> +	return 0;
>> +}
>> +
>>  /* rdtgroup information files for one cache resource. */
>>  static struct rftype res_common_files[] = {
>>  	{
>> @@ -2019,6 +2040,12 @@ static struct rftype res_common_files[] = {
>>  		.seq_show	= mbm_local_bytes_config_show,
>>  		.write		= mbm_local_bytes_config_write,
>>  	},
>> +	{
>> +		.name		= "event_filter",
>> +		.mode		= 0444,
>> +		.kf_ops		= &rdtgroup_kf_single_ops,
>> +		.seq_show	= event_filter_show,
>> +	},
>>  	{
>>  		.name		= "mbm_assign_mode",
>>  		.mode		= 0444,

I am looking at the SDCIAE series now and it really looks like rdtgroup.c is
becoming very large with code from various areas mixed in. In this series I
requested several functions to be moved to monitor.c but generally did not
highlight the main handlers added by this work. For example event_filter_show()
added by this patch. For this work, could you please take a look if the
handlers can also be moved to monitor.c? I think this will make things cleaner
since the same helpers and data structures no longer need to be shared by multiple
resctrl files. For example here, mbm_transactions[] can remain private
to monitor.c where it is most relevant. In retrospect I think this is what
we should have done for the BMEC work also.

Reinette