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

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Message-ID: <6850dc71-e709-42ce-9113-9cb5a7a590f7@linux.intel.com>
Date:   Thu, 19 Oct 2023 10:28:52 -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 7:00 a.m., Peter Zijlstra wrote:
> On Wed, Oct 04, 2023 at 11:40:41AM -0700, kan.liang@...ux.intel.com wrote:
> 
>> +static ssize_t branch_counter_width_show(struct device *cdev,
>> +					 struct device_attribute *attr,
>> +					 char *buf)
>> +{
>> +	return snprintf(buf, PAGE_SIZE, "2\n");
>> +}
> 
>> +#define ARCH_LBR_EVENT_LOG_WIDTH	2
> 
> I'm assuming this is the same '2' ? And having it hard-coded in two
> locations is awesome..
> 
>> +#define ARCH_LBR_EVENT_LOG_MASK		0x3
> 
> Should probably be ((1<<2)-1)
> 
> As per that other email, the naming is confusing, should this not be:
> 
> ARCH_LBR_EVENT_COUNTER_BITS
> 
> or, since it's all local to lbr.c something shorter still, like:
> 
> LBR_COUNTER_BITS
> 
> hmm?

Sure, I will use the name LBR_COUNTER_BITS.

Thanks,
Kan