linux-kernel - Re: [PATCH] perf pmu: Fix alias matching

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Date:   Wed, 21 Jul 2021 08:37:38 +0100
From:   John Garry <john.garry@...wei.com>
To:     "Jin, Yao" <yao.jin@...ux.intel.com>, <peterz@...radead.org>,
        <mingo@...hat.com>, <acme@...nel.org>, <mark.rutland@....com>,
        <jolsa@...hat.com>, <namhyung@...nel.org>, <kjain@...ux.ibm.com>,
        <alexander.shishkin@...ux.intel.com>, <irogers@...gle.com>
CC:     <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf pmu: Fix alias matching

>>
>> Fixes: c47a5599eda3 ("perf tools: Fix pattern matching for same 
>> substring in different PMU type")
>> Signed-off-by: John Garry <john.garry@...wei.com>
>> ---
>> @Jin Yao, please test for your scenarios
>>
> 
> For x86, the form uncore_pmu_{digits} or the uncore_pmu itself are 
> supported. We don't have more complex case such as the name in the form 
> aaa_bbbX_cccY. So my test didn't cover that complex form.
> 

My next thing to do is to add support for these more complex scenarios 
in the PMU events self tests

> For my test, your patch works, thanks! :)

Good

> 
>> Note:
>> About any effect in perf_pmu__match() -> perf_pmu__valid_suffix()
>> callchain, this seems to be called for wildcard in PMU names in metric
>> expressions. We don't have any metrics for arm64 which use feature.
>> However, I hacked an existing metric to use a wildcard and it looks ok.
>> Also the "DRAM_BW_Use" metric on my broadwell uses this feature, and it
>> looks ok.
>>
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index a1bd7007a8b4..fc683bc41715 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -742,9 +742,13 @@ struct pmu_events_map *__weak 
>> pmu_events_map__find(void)
>>       return perf_pmu__find_map(NULL);
>>   }
>> -static bool perf_pmu__valid_suffix(char *pmu_name, char *tok)
>> +/*
>> + * Suffix must be in form tok_{digits}, or tok{digits}, or same as 
>> pmu_name
>> + * to be valid.
>> + */
>> +static bool perf_pmu__valid_suffix(const char *pmu_name, char *tok)
>>   {
>> -    char *p;
>> +    const char *p;
>>       if (strncmp(pmu_name, tok, strlen(tok)))
>>           return false;
>> @@ -753,12 +757,16 @@ static bool perf_pmu__valid_suffix(char 
>> *pmu_name, char *tok)
>>       if (*p == 0)
>>           return true;
>> -    if (*p != '_')
>> -        return false;
>> +    if (*p == '_')
>> +        ++p;
>> -    ++p;
>> -    if (*p == 0 || !isdigit(*p))
>> -        return false;
>> +    /* Ensure we end in a number */
>> +    while (1) {
>> +        if (!isdigit(*p))
>> +            return false;
>> +        if (*(++p) == 0)
>> +            break;
>> +    }
> 
> Do we check *p before first isdigit? For example,
> 
> if (*p == 0)
>      return false;
> 
> While (*p) {
>      if (!isdigit(*p)
>          return false;
>      ++p;
> }
> 
> But maybe isdigit can handle the null string well. I'm just feeling a 
> bit unsure.
> 

isdigit() can safely handle 0 and returns 0 for that case, so what I 
added should be ok

>>       return true;
>>   }
>> @@ -789,12 +797,19 @@ bool pmu_uncore_alias_match(const char 
>> *pmu_name, const char *name)
>>        *        match "socket" in "socketX_pmunameY" and then 
>> "pmuname" in
>>        *        "pmunameY".
>>        */
>> -    for (; tok; name += strlen(tok), tok = strtok_r(NULL, ",", &tmp)) {
>> +    while (1) {
>> +        char *next_tok = strtok_r(NULL, ",", &tmp);
>> +
>>           name = strstr(name, tok);
>> -        if (!name || !perf_pmu__valid_suffix((char *)name, tok)) {
>> +        if (!name ||
>> +            (!next_tok && !perf_pmu__valid_suffix(name, tok))) {
>>               res = false;
>>               goto out;
>>           }
>> +        if (!next_tok)
>> +            break;
>> +        tok = next_tok;
>> +        name += strlen(tok);
>>       }
>>       res = true;
>>
> 
> My test didn't cover the tokens which were delimited by ','. I assume 
> you have tested that on arm64 system. :)
> 

Right
Thanks,
John