linux-kernel - Re: [PATCH 3/3] perf list: Support filtering in JSON output

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Message-ID: <CAP-5=fXBhg3M0JdE6rEF+Gh1KDBdcd=onVgGegWv4GG6Jw2U9Q@mail.gmail.com>
Date: Wed, 19 Nov 2025 08:42:50 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, James Clark <james.clark@...aro.org>, 
	Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 3/3] perf list: Support filtering in JSON output

On Mon, Nov 17, 2025 at 10:36 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Like regular output mode, it should honor command line arguments to
> limit to a certain type of PMUs or events.
>
>   $ perf list -j hw
>   [
>   {
>           "Unit": "cpu",
>           "Topic": "legacy hardware",
>           "EventName": "branch-instructions",
>           "EventType": "Kernel PMU event",
>           "BriefDescription": "Retired branch instructions [This event is an alias of branches]",
>           "Encoding": "cpu/event=0xc4\n/"

The new-line '\n' here looks like another bug, the bug is coming from
reading the event from sysfs but not stripping any '\n'.

This change lgtm but we need to figure out the struct json_print_state
in patch 2.

Thanks,
Ian

>   },
>   {
>           "Unit": "cpu",
>           "Topic": "legacy hardware",
>           "EventName": "branch-misses",
>           "EventType": "Kernel PMU event",
>           "BriefDescription": "Mispredicted branch instructions",
>           "Encoding": "cpu/event=0xc5\n/"
>   },
>   ...
>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/builtin-list.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/tools/perf/builtin-list.c b/tools/perf/builtin-list.c
> index 1ab969ffe371c5cb..48c799007414bf6e 100644
> --- a/tools/perf/builtin-list.c
> +++ b/tools/perf/builtin-list.c
> @@ -375,6 +375,21 @@ static void json_print_event(void *ps, const char *topic,
>         FILE *fp = print_state->fp;
>         struct strbuf buf;
>
> +       if (deprecated && !print_state->deprecated)
> +               return;
> +
> +       if (print_state->pmu_glob && (!pmu_name || !strglobmatch(pmu_name, print_state->pmu_glob)))
> +               return;
> +
> +       if (print_state->exclude_abi && pmu_type < PERF_TYPE_MAX && pmu_type != PERF_TYPE_RAW)
> +               return;
> +
> +       if (print_state->event_glob &&
> +           (!event_name || !strglobmatch(event_name, print_state->event_glob)) &&
> +           (!event_alias || !strglobmatch(event_alias, print_state->event_glob)) &&
> +           (!topic || !strglobmatch_nocase(topic, print_state->event_glob)))
> +               return;
> +
>         strbuf_init(&buf, 0);
>         fprintf(fp, "%s{\n", print_state->need_sep ? ",\n" : "");
>         print_state->need_sep = true;
> @@ -451,6 +466,11 @@ static void json_print_metric(void *ps __maybe_unused, const char *group,
>         FILE *fp = print_state->fp;
>         struct strbuf buf;
>
> +       if (print_state->event_glob &&
> +           (!print_state->metrics || !name || !strglobmatch(name, print_state->event_glob)) &&
> +           (!print_state->metricgroups || !group || !strglobmatch(group, print_state->event_glob)))
> +               return;
> +
>         strbuf_init(&buf, 0);
>         fprintf(fp, "%s{\n", print_state->need_sep ? ",\n" : "");
>         print_state->need_sep = true;
> --
> 2.52.0.rc1.455.g30608eb744-goog
>