linux-kernel - Re: [RFC PATCH v2 07/13] perf pmu: Add pmu

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Message-ID: <1b2c2b91-173b-2656-597c-551aac750784@huawei.com>
Date:   Wed, 22 Apr 2020 12:54:54 +0100
From:   John Garry <john.garry@...wei.com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <namhyung@...nel.org>, <will@...nel.org>, <ak@...ux.intel.com>,
        <linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>,
        <qiangqing.zhang@....com>, <irogers@...gle.com>,
        <robin.murphy@....com>, <zhangshaokun@...ilicon.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v2 07/13] perf pmu: Add pmu_id()

  Wi
On 22/04/2020 12:41, Jiri Olsa wrote:
> On Fri, Apr 17, 2020 at 06:41:18PM +0800, John Garry wrote:
>> Add a function to read the PMU id sysfs entry. We only do it for uncore
>> PMUs where this would be relevant.
>>
>> Signed-off-by: John Garry <john.garry@...wei.com>
>> ---
>>   tools/perf/util/pmu.c | 36 ++++++++++++++++++++++++++++++++++++
>>   tools/perf/util/pmu.h |  1 +
>>   2 files changed, 37 insertions(+)
>>
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index ef6a63f3d386..6a67c6a28d08 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -594,6 +594,7 @@ static struct perf_cpu_map *__pmu_cpumask(const char *path)
>>    * Uncore PMUs have a "cpumask" file under sysfs. CPU PMUs (e.g. on arm/arm64)
>>    * may have a "cpus" file.
>>    */
>> +#define CPUS_TEMPLATE_ID	"%s/bus/event_source/devices/%s/identifier"
>>   #define CPUS_TEMPLATE_UNCORE	"%s/bus/event_source/devices/%s/cpumask"
>>   #define CPUS_TEMPLATE_CPU	"%s/bus/event_source/devices/%s/cpus"
>>   
>> @@ -632,6 +633,39 @@ static bool pmu_is_uncore(const char *name)
>>   	return file_available(path);
>>   }
>>   
>> +static char *pmu_id(const char *name)
>> +{
>> +	char path[PATH_MAX], *id;
>> +	const char *sysfs;
>> +	FILE *file;
>> +	int n;
>> +
>> +	sysfs = sysfs__mountpoint();
>> +	snprintf(path, PATH_MAX, CPUS_TEMPLATE_ID, sysfs, name);
>> +
>> +	id = malloc(PATH_MAX);
>> +	if (!id)
>> +		return NULL;
>> +
>> +	file = fopen(path, "r");
>> +	if (!file) {
>> +		free(id);
>> +		return NULL;
>> +	}
>> +
>> +	n = fscanf(file, "%s", id);
>> +
>> +	fclose(file);
>> +
>> +	if (!n) {
>> +		free(id);
>> +		return NULL;
>> +	}
>> +
>> +	return id;
>> +}
> 
> I still need to go through this patchset in more detail,

ok, great.

But, could you check patch #1 also, as this *may* be fixing something 
broken in mainline? Not sure. Without it, we get a spew of warnings for 
metrics.

> but just quick note, that we have sysfs__read_str that you
> could use in here
> 

ok, there may be more functions in current pmu.c then which can use 
this. I can check.

Cheers,
John