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

Liang, Kan
2020-03-10T16:54:12Z

On 3/10/2020 10:04 AM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Mar 10, 2020 at 09:53:24AM -0400, Liang, Kan escreveu:
>> 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:
>>>> +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, overall just consider making the patches smaller if possible,
> with prep patches paving the way for more complex changes so that
> reviewing becomes easier, for instance:
>
> perf machine: Refine the function for LBR call stack reconstruction
>
> Seems to do too many things at once. It was unfortunate, for instance,
> that the pre-existing code had that
>
> resolve_lbr_callchain_sample()
> {
> /* LBR only affects the user callchain */
> if (i != chain_nr) {
> body of the function, long
> ....
> return err;
> }
>
> return 0;
> }
>
> One of the things you did in this patch was to the more sensible:
>
> /* LBR only affects the user callchain */
> if (i == chain_nr)
> return 0;
>
> body of the function
> ...
> return err;
>
> So if you had a prep patch at this point just removing that silly
> indent, then we would see that that is just removing the indent, the
> next patch wouldn't have that check for user callchains, would be
> smaller, I think that would help reduce the patch sizes.
>
> Then if you just moved to a separate function the (callchain_param.order
> == ORDER_CALLEE) part, the patch would again be smaller, etc.
>
> This helps reviewing and usually helps us later, with bisection, when
> some bug is introduced,

Sure, I will go through all patches and see what I can do to reduce the
size of patches in V3.

Thanks,
Kan

>
> Regards,
>
> - Arnaldo
>
>> 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
>>>>
>>>
>