linux-kernel - Re: [PATCH v2 3/3] perf list: Support filtering in JSON output

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Message-ID: <CAP-5=fWHTGSZPDO06FJENFLW0AtS1Fukk1jqFeHqyGFa+HLhMw@mail.gmail.com>
Date: Wed, 19 Nov 2025 21:42:51 -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 v2 3/3] perf list: Support filtering in JSON output

On Wed, Nov 19, 2025 at 4:47 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/"
>   },
>   {
>           "Unit": "cpu",
>           "Topic": "legacy hardware",
>           "EventName": "branch-misses",
>           "EventType": "Kernel PMU event",
>           "BriefDescription": "Mispredicted branch instructions",
>           "Encoding": "cpu/event=0xc5\n/"

I think these newlines can be fixed by changing:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/pmu.c?h=perf-tools-next#n643
```
ret = io__getline(&io, &alias->terms, &line_len) < 0 ? -errno : 0;
if (ret) {
   ...
}
```
to something like:
```
ret = io__getline(&io, &alias->terms, &line_len) < 0 ? -errno : 0;
if (ret) {
    ...
}
if (alias->terms[line_len - 1] == '\n')
    alias->terms[line_len - 1] = '\0';
```

>   },
>   ...
>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>

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

Thanks,
Ian

> ---
>  tools/perf/builtin-list.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/tools/perf/builtin-list.c b/tools/perf/builtin-list.c
> index 6c5913f129f39c94..5cbca0bacd35237e 100644
> --- a/tools/perf/builtin-list.c
> +++ b/tools/perf/builtin-list.c
> @@ -373,6 +373,23 @@ static void json_print_event(void *ps, const char *topic,
>         FILE *fp = print_state->common.fp;
>         struct strbuf buf;
>
> +       if (deprecated && !print_state->common.deprecated)
> +               return;
> +
> +       if (print_state->common.pmu_glob &&
> +           (!pmu_name || !strglobmatch(pmu_name, print_state->common.pmu_glob)))
> +               return;
> +
> +       if (print_state->common.exclude_abi && pmu_type < PERF_TYPE_MAX &&
> +           pmu_type != PERF_TYPE_RAW)
> +               return;
> +
> +       if (print_state->common.event_glob &&
> +           (!event_name || !strglobmatch(event_name, print_state->common.event_glob)) &&
> +           (!event_alias || !strglobmatch(event_alias, print_state->common.event_glob)) &&
> +           (!topic || !strglobmatch_nocase(topic, print_state->common.event_glob)))
> +               return;
> +
>         strbuf_init(&buf, 0);
>         fprintf(fp, "%s{\n", print_state->need_sep ? ",\n" : "");
>         print_state->need_sep = true;
> @@ -449,6 +466,13 @@ static void json_print_metric(void *ps __maybe_unused, const char *group,
>         FILE *fp = print_state->common.fp;
>         struct strbuf buf;
>
> +       if (print_state->common.event_glob &&
> +           (!print_state->common.metrics || !name ||
> +            !strglobmatch(name, print_state->common.event_glob)) &&
> +           (!print_state->common.metricgroups || !group ||
> +            !strglobmatch(group, print_state->common.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
>