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

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Date:   Mon, 28 Jun 2021 09:52:42 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        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 Jiri,

On 6/25/2021 6:11 PM, Jiri Olsa wrote:
> On Wed, Jun 23, 2021 at 10:02:01AM +0800, Jin, Yao wrote:
>> Hi Arnaldo, Jiri,
>>
>> Any comments for this bug fix patch?
>>
>> The issue does impact some uncore events and even some metrics.
> 
> sry for delay
> 
> SNIP
> 
>>>> 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;
> 
> could this be part of the fnmatch's pattern?
>

Actually I had used the pattern "uncore_imc_[0-9]" before. But for some units, e.g., CHA, they have 
more than 10 units. So this simple pattern couldn't satisfy them.

And then I changed the pattern to "uncore_imc_[0-9]+$", which can match the string 
"uncore_imc_<integer id>". But unfortunately it didn't work for fnmatch.

I used regex, such as:

asprintf(&pattern, "%s_[0-9]+$", tok);
regcomp(&regex, pattern, REG_EXTENDED);
ret = regexec(&regex, name, 0, NULL, 0);

But the regex approach looks not very simple (a bit heavy), so finally I just keep using fnmatch and 
then just check the last character.

>>>>                    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;
>>>> +}
> 
> hum, so we have pattern serch and then another function checking
> if that search was ok..

Yes, that's what this patch does.

I understand that's convenient, because
> it's on 2 different places

Yes, on pmu_uncore_alias_match() and on parse-events.y.

but could we have some generic solution,
> line one function/search that returns/search for valid pmu name?
> 

Sorry, I don't understand this idea well. Would you like to further explain?

Or can you accept the regex approach?

> thanks,
> jirka
>