linux-kernel - Re: [PATCH v1] perf tools: Fix pattern matching for same substring used in different pmu type

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Date:   Wed, 23 Jun 2021 10:02:01 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com
Cc:     Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v1] perf tools: Fix pattern matching for same substring
 used in different pmu type

Hi Arnaldo, Jiri,

Any comments for this bug fix patch?

The issue does impact some uncore events and even some metrics.

Thanks
Jin Yao

On 6/11/2021 10:54 AM, Jin, Yao wrote:
> And, though this patch is to fix the uncore_imc/uncore_imc_free_running mismatching issue. We are 
> also surprised to see it can solve another hybrid PMU issue on Alderlake.
> 
> On Alderlake,
> 
> # ./perf stat -e cpu/event=0xc2,umask=0x2/ true
> 
> Performance counter stats for 'true':
> 
>             702,246      cpu_core/event=0xc2,umask=0x2/
>       <not counted>      cpu_atom/event=0xc2,umask=0x2/
> 
> It should error out with the wrong PMU rather than using 'cpu_core' and'cpu_atom' instead.
> 
> This is still the pattern matching issue. The pattern is "cpu*". Both "cpu_core" and "cpu_atom" can 
> match the pattern "cpu*", so the parser wrongly thinks they are the same PMU type.
> 
> Now with this patch,
> 
> # ./perf stat -e cpu/cpu-cycles/ true
> event syntax error: 'cpu/cpu-cycles/'
>                       \___ Cannot find PMU `cpu'. Missing kernel support?
> Run 'perf list' for a list of valid events
> 
> Thanks
> Jin Yao
> 
> On 6/9/2021 12:57 PM, Jin Yao wrote:
>> Some different pmu types may have same substring. For example,
>> on Icelake server, we have pmu types "uncore_imc" and
>> "uncore_imc_free_running". Both pmu types have substring "uncore_imc".
>> But the parser would wrongly think they are the same pmu type.
>>
>> We enable an imc event,
>> perf stat -e uncore_imc/event=0xe3/ -a -- sleep 1
>>
>> Perf actually expands the event to:
>> uncore_imc_0/event=0xe3/
>> uncore_imc_1/event=0xe3/
>> uncore_imc_2/event=0xe3/
>> uncore_imc_3/event=0xe3/
>> uncore_imc_4/event=0xe3/
>> uncore_imc_5/event=0xe3/
>> uncore_imc_6/event=0xe3/
>> uncore_imc_7/event=0xe3/
>> uncore_imc_free_running_0/event=0xe3/
>> uncore_imc_free_running_1/event=0xe3/
>> uncore_imc_free_running_3/event=0xe3/
>> uncore_imc_free_running_4/event=0xe3/
>>
>> That's because the "uncore_imc_free_running" matches the
>> pattern "uncore_imc*".
>>
>> Now we check that the last characters of pmu name is
>> '_<digit>'.
>>
>> Fixes: b2b9d3a3f021 ("perf pmu: Support wildcards on pmu name in dynamic pmu events")
>> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
>> ---
>>   tools/perf/util/parse-events.y |  2 ++
>>   tools/perf/util/pmu.c          | 25 ++++++++++++++++++++++++-
>>   tools/perf/util/pmu.h          |  1 +
>>   3 files changed, 27 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
>> index aba12a4d488e..7a694c7f7f1a 100644
>> --- a/tools/perf/util/parse-events.y
>> +++ b/tools/perf/util/parse-events.y
>> @@ -317,6 +317,8 @@ event_pmu_name opt_pmu_config
>>                   strncmp($1, "uncore_", 7))
>>                   name += 7;
>>               if (!fnmatch(pattern, name, 0)) {
>> +                if (!perf_pmu__valid_suffix($1, name))
>> +                    continue;
>>                   if (parse_events_copy_term_list(orig_terms, &terms))
>>                       CLEANUP_YYABORT;
>>                   if (!parse_events_add_pmu(_parse_state, list, pmu->name, terms, true, false))
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 88c8ecdc60b0..78af01959830 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -3,6 +3,7 @@
>>   #include <linux/compiler.h>
>>   #include <linux/string.h>
>>   #include <linux/zalloc.h>
>> +#include <linux/ctype.h>
>>   #include <subcmd/pager.h>
>>   #include <sys/types.h>
>>   #include <errno.h>
>> @@ -768,7 +769,7 @@ bool pmu_uncore_alias_match(const char *pmu_name, const char *name)
>>        */
>>       for (; tok; name += strlen(tok), tok = strtok_r(NULL, ",", &tmp)) {
>>           name = strstr(name, tok);
>> -        if (!name) {
>> +        if (!name || !perf_pmu__valid_suffix(tok, (char *)name)) {
>>               res = false;
>>               goto out;
>>           }
>> @@ -1872,3 +1873,25 @@ bool perf_pmu__has_hybrid(void)
>>       return !list_empty(&perf_pmu__hybrid_pmus);
>>   }
>> +
>> +bool perf_pmu__valid_suffix(char *tok, char *pmu_name)
>> +{
>> +    char *p;
>> +
>> +    /*
>> +     * The pmu_name has substring tok. If the format of
>> +     * pmu_name is <tok> or <tok>_<digit>, return true.
>> +     */
>> +    p = pmu_name + strlen(tok);
>> +    if (*p == 0)
>> +        return true;
>> +
>> +    if (*p != '_')
>> +        return false;
>> +
>> +    ++p;
>> +    if (*p == 0 || !isdigit(*p))
>> +        return false;
>> +
>> +    return true;
>> +}
>> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
>> index a790ef758171..ebfd2b71532b 100644
>> --- a/tools/perf/util/pmu.h
>> +++ b/tools/perf/util/pmu.h
>> @@ -133,5 +133,6 @@ void perf_pmu__warn_invalid_config(struct perf_pmu *pmu, __u64 config,
>>                      char *name);
>>   bool perf_pmu__has_hybrid(void);
>> +bool perf_pmu__valid_suffix(char *tok, char *pmu_name);
>>   #endif /* __PMU_H */
>>