linux-kernel - Re: [PATCH v1 1/4] perf parse-events x86: Avoid sorting uops

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Message-ID: <9b3618ee-abe9-745a-01d7-98eb9ab70fc2@linux.intel.com>
Date:   Tue, 1 Aug 2023 13:48:06 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>,
        Weilin Wang <weilin.wang@...el.com>
Subject: Re: [PATCH v1 1/4] perf parse-events x86: Avoid sorting
 uops_retired.slots



On 2023-08-01 11:54 a.m., Ian Rogers wrote:
> On Tue, Aug 1, 2023 at 8:40 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
>>
>>
>>
>> On 2023-08-01 1:36 a.m., Ian Rogers wrote:
>>> As topdown.slots may appear as slots it may get confused with
>>> uops_retired.slots which is an invalid perf metric event group
>>> leader. Special case uops_retired.slots to avoid this confusion.
>>>
>>
>> Does any name with format "name.slots" cause the confusion? If so, I
>> don't think we can stop others from naming like the above format.
>>
>> Is it better to hard code the topdown.slots/slots, rather than
>> uops_retired.slots?
> 
> So firstly, yet more fringe perf metric event benefits with this silly
> bit of complexity. The issue with "just" trying to pattern match
> "topdown.slots" and "slots" is that there may be pmu names in there.
> So (ignoring case) we get:
> 
> slots
> topdown.slots
> cpu/slots/
> cpu/topdown.slots/
> cpu_core/slots/
> cpu_core/topdown.slots/
> 
> but the name can have other junk like modifiers in there and also
> there's the name= config term, but let's just not think about that
> breaking stuff. To avoid 6 searches I searched for the known
> problematic uops_retired.slots, knowing if that's not there then one
> of the 6 above is the match. Searching for just "slots" or
> "topdown.slots" isn't good enough as "slots" will get a hit in
> "uops_retired.slots", how we ended up with this patch in the 1st
> place. So I ended up using the uops_retired.slots search to reduce
> complexity in the code and to avoid writing an event parser just to
> figure out what the name is... Ideally we'd be using the
> perf_event_attr to do this comparison, but immediately after
> parse-events when this code runs it hasn't been computed yet. Maybe I
> can shuffle things around and make this true. Ideally I think
> parse-events would just be a library that given some event description
> gives back perf_event_attr and not evsels, but that's yet further
> work...
>

Thanks for the details.

I don't think we have other events with a similar pattern. For now,
special case uops_retired.slots should be good enough.

Thanks,
Kan

> Thanks,
> Ian
> 
>>
>> Thanks,
>> Kan
>>
>>> Signed-off-by: Ian Rogers <irogers@...gle.com>
>>> ---
>>>  tools/perf/arch/x86/util/evlist.c | 7 ++++---
>>>  tools/perf/arch/x86/util/evsel.c  | 7 +++----
>>>  2 files changed, 7 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/tools/perf/arch/x86/util/evlist.c b/tools/perf/arch/x86/util/evlist.c
>>> index cbd582182932..b1ce0c52d88d 100644
>>> --- a/tools/perf/arch/x86/util/evlist.c
>>> +++ b/tools/perf/arch/x86/util/evlist.c
>>> @@ -75,11 +75,12 @@ int arch_evlist__add_default_attrs(struct evlist *evlist,
>>>
>>>  int arch_evlist__cmp(const struct evsel *lhs, const struct evsel *rhs)
>>>  {
>>> -     if (topdown_sys_has_perf_metrics() && evsel__sys_has_perf_metrics(lhs)) {
>>> +     if (topdown_sys_has_perf_metrics() &&
>>> +         (arch_evsel__must_be_in_group(lhs) || arch_evsel__must_be_in_group(rhs))) {
>>>               /* Ensure the topdown slots comes first. */
>>> -             if (strcasestr(lhs->name, "slots"))
>>> +             if (strcasestr(lhs->name, "slots") && !strcasestr(lhs->name, "uops_retired.slots"))
>>>                       return -1;
>>> -             if (strcasestr(rhs->name, "slots"))
>>> +             if (strcasestr(rhs->name, "slots") && !strcasestr(rhs->name, "uops_retired.slots"))
>>>                       return 1;
>>>               /* Followed by topdown events. */
>>>               if (strcasestr(lhs->name, "topdown") && !strcasestr(rhs->name, "topdown"))
>>> diff --git a/tools/perf/arch/x86/util/evsel.c b/tools/perf/arch/x86/util/evsel.c
>>> index 81d22657922a..090d0f371891 100644
>>> --- a/tools/perf/arch/x86/util/evsel.c
>>> +++ b/tools/perf/arch/x86/util/evsel.c
>>> @@ -40,12 +40,11 @@ bool evsel__sys_has_perf_metrics(const struct evsel *evsel)
>>>
>>>  bool arch_evsel__must_be_in_group(const struct evsel *evsel)
>>>  {
>>> -     if (!evsel__sys_has_perf_metrics(evsel))
>>> +     if (!evsel__sys_has_perf_metrics(evsel) || !evsel->name ||
>>> +         strcasestr(evsel->name, "uops_retired.slots"))
>>>               return false;
>>>
>>> -     return evsel->name &&
>>> -             (strcasestr(evsel->name, "slots") ||
>>> -              strcasestr(evsel->name, "topdown"));
>>> +     return strcasestr(evsel->name, "topdown") || strcasestr(evsel->name, "slots");
>>>  }
>>>
>>>  int arch_evsel__hw_name(struct evsel *evsel, char *bf, size_t size)