Re: [PATCH V2 1/9] perf pmu: Add support for PMU capabilities

Liang, Kan
2020-03-10T13:53:30Z

On 3/10/2020 9:06 AM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 09, 2020 at 10:46:31AM -0700, kan.liang@linux.intel.com escreveu:
>> From: Kan Liang <kan.liang@linux.intel.com>
>>
>> The PMU capabilities information, which is located at
>> /sys/bus/event_source/devices/<dev>/caps, is required by perf tool.
>> For example, the max LBR information is required to stitch LBR call
>> stack.
>>
>> Add perf_pmu__caps_parse() to parse the PMU capabilities information.
>> The information is stored in a list.
>>
>> Add perf_pmu__scan_caps() to scan the capabilities one by one.
>>
>> The following patch will store the capabilities information in perf
>> header.
>>
>> Reviewed-by: Andi Kleen <ak@linux.intel.com>
>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
>> ---
>> tools/perf/util/pmu.c | 87 +++++++++++++++++++++++++++++++++++++++++++
>> tools/perf/util/pmu.h | 12 ++++++
>> 2 files changed, 99 insertions(+)
>>
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 8b99fd312aae..13634ca09096 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -844,6 +844,7 @@ static struct perf_pmu *pmu_lookup(const char *name)
>>
>> INIT_LIST_HEAD(&pmu->format);
>> INIT_LIST_HEAD(&pmu->aliases);
>> + INIT_LIST_HEAD(&pmu->caps);
>> list_splice(&format, &pmu->format);
>> list_splice(&aliases, &pmu->aliases);
>> list_add_tail(&pmu->list, &pmus);
>> @@ -1565,3 +1566,89 @@ int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt,
>> va_end(args);
>> return ret;
>> }
>> +
>> +static int perf_pmu__new_caps(struct list_head *list, char *name, char *value)
>> +{
>> + struct perf_pmu_caps *caps;
>> +
>> + caps = zalloc(sizeof(*caps));
>> + if (!caps)
>> + return -ENOMEM;
>> +
>
> So here you check if zalloc fails and returns a proper error
>
>> + caps->name = strdup(name);
>> + caps->value = strndup(value, strlen(value) - 1);
>
> But then you don't check strdup()?

Right, I should check strdup(), otherwise the capability information may
be incomplete. I will fix it in V3.

Thanks,
Kan

>
>> + list_add_tail(&caps->list, list);
>> + return 0;
>> +}
>> +
>> +/*
>> + * Reading/parsing the given pmu capabilities, which should be located at:
>> + * /sys/bus/event_source/devices/<dev>/caps as sysfs group attributes.
>> + * Return the number of capabilities
>> + */
>> +int perf_pmu__caps_parse(struct perf_pmu *pmu)
>> +{
>> + struct stat st;
>> + char caps_path[PATH_MAX];
>> + const char *sysfs = sysfs__mountpoint();
>> + DIR *caps_dir;
>> + struct dirent *evt_ent;
>> + int nr_caps = 0;
>> +
>> + if (!sysfs)
>> + return -1;
>> +
>> + snprintf(caps_path, PATH_MAX,
>> + "%s" EVENT_SOURCE_DEVICE_PATH "%s/caps", sysfs, pmu->name);
>> +
>> + if (stat(caps_path, &st) < 0)
>> + return 0; /* no error if caps does not exist */
>> +
>> + caps_dir = opendir(caps_path);
>> + if (!caps_dir)
>> + return -EINVAL;
>> +
>> + while ((evt_ent = readdir(caps_dir)) != NULL) {
>> + char path[PATH_MAX + NAME_MAX + 1];
>> + char *name = evt_ent->d_name;
>> + char value[128];
>> + FILE *file;
>> +
>> + if (!strcmp(name, ".") || !strcmp(name, ".."))
>> + continue;
>> +
>> + snprintf(path, sizeof(path), "%s/%s", caps_path, name);
>> +
>> + file = fopen(path, "r");
>> + if (!file)
>> + break;
>> +
>> + if (!fgets(value, sizeof(value), file) ||
>> + (perf_pmu__new_caps(&pmu->caps, name, value) < 0)) {
>> + fclose(file);
>> + break;
>> + }
>> +
>> + nr_caps++;
>> + fclose(file);
>> + }
>> +
>> + closedir(caps_dir);
>> +
>> + return nr_caps;
>> +}
>> +
>> +struct perf_pmu_caps *perf_pmu__scan_caps(struct perf_pmu *pmu,
>> + struct perf_pmu_caps *caps)
>> +{
>> + if (!pmu)
>> + return NULL;
>> +
>> + if (!caps)
>> + caps = list_prepare_entry(caps, &pmu->caps, list);
>> +
>> + list_for_each_entry_continue(caps, &pmu->caps, list)
>> + return caps;
>> +
>> + return NULL;
>> +}
>> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
>> index 6737e3d5d568..a228e27ae462 100644
>> --- a/tools/perf/util/pmu.h
>> +++ b/tools/perf/util/pmu.h
>> @@ -21,6 +21,12 @@ enum {
>>
>> struct perf_event_attr;
>>
>> +struct perf_pmu_caps {
>> + char *name;
>> + char *value;
>> + struct list_head list;
>> +};
>> +
>> struct perf_pmu {
>> char *name;
>> __u32 type;
>> @@ -32,6 +38,7 @@ struct perf_pmu {
>> struct perf_cpu_map *cpus;
>> struct list_head format; /* HEAD struct perf_pmu_format -> list */
>> 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 */
>> };
>>
>> @@ -102,4 +109,9 @@ struct pmu_events_map *perf_pmu__find_map(struct perf_pmu *pmu);
>>
>> int perf_pmu__convert_scale(const char *scale, char **end, double *sval);
>>
>> +int perf_pmu__caps_parse(struct perf_pmu *pmu);
>> +
>> +struct perf_pmu_caps *perf_pmu__scan_caps(struct perf_pmu *pmu,
>> + struct perf_pmu_caps *caps);
>> +
>> #endif /* __PMU_H */
>> --
>> 2.17.1
>>
>