linux-kernel - Re: [PATCH 1/2] perf tools: Always uniquify event names

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Message-ID: <CAP-5=fUJM5GYjSQafR+c_u19PF4_SS=1zFq0nGUHC3=XYYQ+VQ@mail.gmail.com>
Date: Thu, 4 Dec 2025 08:34:34 -0800
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, leo.yan@....com, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] perf tools: Always uniquify event names

On Thu, Dec 4, 2025 at 1:11 AM James Clark <james.clark@...aro.org> wrote:
>
> evlist__uniquify_evsel_names() only gets called in __parse_events() if
> verbose is > 0. This means that the auto added "slots" events stay as
> "slots" rather than being expanded to "cpu_core/slots/" unless Perf is
> run in verbose mode. This is invisible to users when running Perf stat
> because evlist__print_counters() always calls it regardless of verbose
> mode before displaying.
>
> The only thing this seems to affect is the test "Parsing of all PMU
> events from sysfs" which fails when not run in verbose mode.
> test__checkevent_pmu_events() always expects event names to be prefixed
> with the pmu name, but this only happens for "slots" events after
> evlist__uniquify_evsel_names() is called.
>
> One fix could be to relax the test to accept the non prefixed name in
> normal mode. But seeing as Perf stat uniquifies unconditionally, make
> parse_events() do the same.
>
> This fixes the following test failure:
>
>   $ perf test "Parsing of all PMU events from sysfs"
>   5.2: Parsing of all PMU events from sysfs                    : FAILED!
>
> Signed-off-by: James Clark <james.clark@...aro.org>

Reviewed-by: Ian Rogers <irogers@...gle.com>

I wonder if we should just always uniquify event names. It could be a
thing that is changing as more and more PMUs are available. I'm
reminded that we used to uniquify sometimes with "<event> [<pmu>]"
prior to commit 057f8bfc6f70 ("perf stat: Uniquify event name
improvements").

Thanks,
Ian

> ---
>  tools/perf/util/parse-events.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 17c1c36a7bf9..50e88c9d3d46 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -2217,12 +2217,12 @@ int __parse_events(struct evlist *evlist, const char *str, const char *pmu_filte
>         evlist__splice_list_tail(evlist, &parse_state.list);
>
>         if (ret2 && warn_if_reordered && !parse_state.wild_card_pmus) {
> +               evlist__uniquify_evsel_names(evlist, &stat_config);
>                 pr_warning("WARNING: events were regrouped to match PMUs\n");
>
>                 if (verbose > 0) {
>                         struct strbuf sb = STRBUF_INIT;
>
> -                       evlist__uniquify_evsel_names(evlist, &stat_config);
>                         evlist__format_evsels(evlist, &sb, 2048);
>                         pr_debug("evlist after sorting/fixing: '%s'\n", sb.buf);
>                         strbuf_release(&sb);
>
> --
> 2.34.1
>