linux-kernel - Re: [PATCH 28/49] perf pmu: Save detected hybrid pmus to a global pmu list

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Date:   Tue, 9 Feb 2021 08:05:31 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        kan.liang@...ux.intel.com
Cc:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, bp@...en8.de,
        namhyung@...nel.org, jolsa@...hat.com, ak@...ux.intel.com,
        alexander.shishkin@...ux.intel.com, adrian.hunter@...el.com,
        "Jin, Yao" <yao.jin@...el.com>
Subject: Re: [PATCH 28/49] perf pmu: Save detected hybrid pmus to a global pmu
 list

Hi Arnaldo,

On 2/9/2021 2:55 AM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Feb 08, 2021 at 07:25:25AM -0800, kan.liang@...ux.intel.com escreveu:
>> From: Jin Yao <yao.jin@...ux.intel.com>
>>
>> We identify the cpu_core pmu and cpu_atom pmu by explicitly
>> checking following files:
>>
>> For cpu_core, check:
>> "/sys/bus/event_source/devices/cpu_core/cpus"
>>
>> For cpu_atom, check:
>> "/sys/bus/event_source/devices/cpu_atom/cpus"
>>
>> If the 'cpus' file exists, the pmu exists.
>>
>> But in order not to hardcode the "cpu_core" and "cpu_atom",
>> and make the code generic, if the path
>> "/sys/bus/event_source/devices/cpu_xxx/cpus" exists, the hybrid
>> pmu exists. All the detected hybrid pmus are linked to a
>> global list 'perf_pmu__hybrid_pmus' and then next we just need
>> to iterate the list by using perf_pmu__for_each_hybrid_pmus.
>>
>> Reviewed-by: Andi Kleen <ak@...ux.intel.com>
>> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
>> ---
>>   tools/perf/util/pmu.c | 21 +++++++++++++++++++++
>>   tools/perf/util/pmu.h |  7 +++++++
>>   2 files changed, 28 insertions(+)
>>
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 0c25457..e97b121 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -27,6 +27,7 @@
>>   #include "fncache.h"
>>   
>>   struct perf_pmu perf_pmu__fake;
>> +LIST_HEAD(perf_pmu__hybrid_pmus);
>>   
>>   struct perf_pmu_format {
>>   	char *name;
>> @@ -633,11 +634,27 @@ static struct perf_cpu_map *pmu_cpumask(const char *name)
>>   	return NULL;
>>   }
>>   
>> +static bool pmu_is_hybrid(const char *name)
>> +{
>> +	char path[PATH_MAX];
>> +	const char *sysfs;
>> +
>> +	if (strncmp(name, "cpu_", 4))
>> +		return false;
>> +
>> +	sysfs = sysfs__mountpoint();
> 
> Its extremely unlikely that sysfs isn't mounted, but if so, this will
> NULL deref, so please do as other sysfs__mountpoint() uses in
> tools/perf/util/pmu.c and check if sysfs is NULL, returning false, i.e.
> file isn't available.
> 

Yes, I need to check the return value of sysfs__mountpoint(), something like.

sysfs = sysfs__mountpoint();
if (!sysfs)
	return false;

>> +	snprintf(path, PATH_MAX, CPUS_TEMPLATE_CPU, sysfs, name);
>> +	return file_available(path);
>> +}
>> +
>>   static bool pmu_is_uncore(const char *name)
>>   {
>>   	char path[PATH_MAX];
>>   	const char *sysfs;
>>   
>> +	if (pmu_is_hybrid(name))
>> +		return false;
>> +
>>   	sysfs = sysfs__mountpoint();
>>   	snprintf(path, PATH_MAX, CPUS_TEMPLATE_UNCORE, sysfs, name);
>>   	return file_available(path);
>> @@ -951,6 +968,7 @@ static struct perf_pmu *pmu_lookup(const char *name)
>>   	pmu->is_uncore = pmu_is_uncore(name);
>>   	if (pmu->is_uncore)
>>   		pmu->id = pmu_id(name);
>> +	pmu->is_hybrid = pmu_is_hybrid(name);
>>   	pmu->max_precise = pmu_max_precise(name);
>>   	pmu_add_cpu_aliases(&aliases, pmu);
>>   	pmu_add_sys_aliases(&aliases, pmu);
>> @@ -962,6 +980,9 @@ static struct perf_pmu *pmu_lookup(const char *name)
>>   	list_splice(&aliases, &pmu->aliases);
>>   	list_add_tail(&pmu->list, &pmus);
>>   
>> +	if (pmu->is_hybrid)
>> +		list_add_tail(&pmu->hybrid_list, &perf_pmu__hybrid_pmus);
>> +
>>   	pmu->default_config = perf_pmu__get_default_config(pmu);
>>   
>>   	return pmu;
>> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
>> index 0e724d5..99bdb5d 100644
>> --- a/tools/perf/util/pmu.h
>> +++ b/tools/perf/util/pmu.h
>> @@ -5,6 +5,7 @@
>>   #include <linux/bitmap.h>
>>   #include <linux/compiler.h>
>>   #include <linux/perf_event.h>
>> +#include <linux/list.h>
>>   #include <stdbool.h>
>>   #include "parse-events.h"
>>   #include "pmu-events/pmu-events.h"
>> @@ -34,6 +35,7 @@ struct perf_pmu {
>>   	__u32 type;
>>   	bool selectable;
>>   	bool is_uncore;
>> +	bool is_hybrid;
>>   	bool auxtrace;
>>   	int max_precise;
>>   	struct perf_event_attr *default_config;
>> @@ -42,9 +44,11 @@ struct perf_pmu {
>>   	struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
>>   	struct list_head caps;    /* HEAD struct perf_pmu_caps -> list */
>>   	struct list_head list;    /* ELEM */
>> +	struct list_head hybrid_list;
>>   };
>>   
>>   extern struct perf_pmu perf_pmu__fake;
>> +extern struct list_head perf_pmu__hybrid_pmus;
>>   
>>   struct perf_pmu_info {
>>   	const char *unit;
>> @@ -124,4 +128,7 @@ int perf_pmu__convert_scale(const char *scale, char **end, double *sval);
>>   
>>   int perf_pmu__caps_parse(struct perf_pmu *pmu);
>>   
>> +#define perf_pmu__for_each_hybrid_pmus(pmu)	\
> 
> singular, i.e.
> 
> #define perf_pmu__for_each_hybrid_pmu(pmu)	\
>

Got it. Will use perf_pmu__for_each_hybrid_pmu in next version.

Thanks
Jin Yao

>> +	list_for_each_entry(pmu, &perf_pmu__hybrid_pmus, hybrid_list)
>> +
>>   #endif /* __PMU_H */
>> -- 
>> 2.7.4
>>
>