linux-kernel - Re: [PATCH V4 4/7] perf/x86/intel: Support LBR event logging

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Date:   Thu, 19 Oct 2023 09:58:30 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, acme@...nel.org, linux-kernel@...r.kernel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, irogers@...gle.com,
        adrian.hunter@...el.com, ak@...ux.intel.com, eranian@...gle.com,
        alexey.v.bayduraev@...ux.intel.com, tinghao.zhang@...el.com
Subject: Re: [PATCH V4 4/7] perf/x86/intel: Support LBR event logging



On 2023-10-19 5:26 a.m., Peter Zijlstra wrote:
> On Wed, Oct 04, 2023 at 11:40:41AM -0700, kan.liang@...ux.intel.com wrote:
> 
>> +
>>  static struct attribute *lbr_attrs[] = {
>>  	&dev_attr_branches.attr,
>> +	&dev_attr_branch_counter_nr.attr,
>> +	&dev_attr_branch_counter_width.attr,
>>  	NULL
>>  };
>>  
>> @@ -5590,7 +5665,11 @@ mem_is_visible(struct kobject *kobj, struct attribute *attr, int i)
>>  static umode_t
>>  lbr_is_visible(struct kobject *kobj, struct attribute *attr, int i)
>>  {
>> -	return x86_pmu.lbr_nr ? attr->mode : 0;
>> +	/* branches */
>> +	if (i == 0)
>> +		return x86_pmu.lbr_nr ? attr->mode : 0;
>> +
>> +	return (x86_pmu.flags & PMU_FL_LBR_EVENT) ? attr->mode : 0;
>>  }
> 
> As in the patch this is fairly readable, but I just checked and in the
> code lbr_attrs and lbr_is_visible() are rather far away from one another
> which makes the whole i thing hard to interpret.
> 
> Should we re-organize that a little?

Sure, I will implement a separate patch to re-organize it.

It seems there are only two attribute groups which have both .attrs and
.is_visible, group_default and group_caps_lbr. I will re-organize for
both of them.

Thanks,
Kan