Re: [PATCH 2/3] perf alias: Rebuild alias expression string to make it comparable

Thomas-Mich Richter
2018-06-15T09:09:18Z

On 06/15/2018 10:12 AM, Jiri Olsa wrote:
> On Thu, Jun 14, 2018 at 08:53:14AM -0500, Paul Clarke wrote:
>
> SNIP
>
>>> + if (ret)
>>> + ret += scnprintf(newval + ret, sizeof(newval) - ret,
>>> + ",");
>>> + if (term->type_val == PARSE_EVENTS__TERM_TYPE_NUM)
>>> + ret += scnprintf(newval + ret, sizeof(newval) - ret,
>>> + "%s=%#x", term->config, term->val.num);
>>> + else if (term->type_val == PARSE_EVENTS__TERM_TYPE_STR)
>>> + ret += scnprintf(newval + ret, sizeof(newval) - ret,
>>> + "%s=%s", term->config, term->val.str);
>>
>> If we exceed 256, we just suddenly terminate the rebuilding without reporting any issues.
>>
>>> + }
>>> +
>>> alias->name = strdup(name);
>>> if (dir) {
>>> /*
>>> @@ -285,7 +308,7 @@ static int __perf_pmu__new_alias(struct list_head *list, char *dir, char *name,
>>> snprintf(alias->unit, sizeof(alias->unit), "%s", unit);
>>> }
>>> alias->per_pkg = perpkg && sscanf(perpkg, "%d", &num) == 1 && num == 1;
>>> - alias->str = strdup(val);
>>> + alias->str = strdup(newval);
>
> hum, how is newval different from val? AFAICS it's the same
>

Not really, depends on the platform, here is some debug output from s390:
root@s35lp76 perf]# ./perf stat -e tx_nc_tend -- ~/mytesttx 1 >/tmp/111

Performance counter stats for '/root/mytesttx 1':

1 tx_nc_tend

0.001050150 seconds time elapsed

[root@s35lp76 perf]# fgrep -i tx_nc_tend /tmp/111
__perf_pmu__new_alias TX_NC_TEND val:event=0x008d newval:event=0x8d
__perf_pmu__new_alias tx_nc_tend val:event=0x8d newval:event=0x8d
TX_NC_TEND 1 rc 8
[root@s35lp76 perf]#

On s390 the events in the PMU sysfs file are printed with leading zeroes.
This means the strcmp() of alias->str differs, but the contents is logically
identical. (Same of some files contains spaces).

Thats why I do the rewrite of val into newval.

The alias name does not match too, but we use strcasecmp() to ignore case.

Hope this helps.
--
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
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