Re: [PATCH] perf stat: Add --hide-zero-events option to suppress zero-count events

[Ian Rogers]

On Thu, Jul 16, 2026 at 7:31 PM Aaron Tomlin <atomlin@xxxxxxxxxxx> wrote:
>
> When monitoring a large number of events (e.g., with wildcards such as
> --event 'syscalls:sys_enter_*'), many matched events will return a count
> of zero. This clutters the output, making it difficult to spot the
> active events.
>
> Add a new option --hide-zero-events to suppress printing events that
> have a count of zero.
>
> To prevent formatting and diagnostic issues, the zero-skipping logic
> implements the following rules:
>
>     1. In metric-only mode (i.e., --metric-only), columns must remain
>        aligned in the output grid. We evaluate config->metric_only first
>        to avoid skipping zero-valued columns, preventing values from
>        shifting left and aligning under incorrect headers
>
>     2. For explicitly requested events, we ensure they are not silently
>        hidden if they are unsupported. We only hide a zero-count event
>        if counter->supported is true, ensuring that unsupported explicit
>        events still report "<not supported>"
>
> Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxxx>

I think this makes sense but perhaps the Python interface makes more
sense for what you're doing. For example, the ilist app shows all
events and metrics:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/python/ilist.py?h=perf-tools-next

Perhaps we could also add some tests for better coverage:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/tests/shell/stat.sh?h=perf-tools-next

Other than that:
Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

> ---
>  tools/perf/Documentation/perf-stat.txt | 3 +++
>  tools/perf/builtin-stat.c              | 2 ++
>  tools/perf/util/stat-display.c         | 3 +++
>  tools/perf/util/stat.h                 | 1 +
>  4 files changed, 9 insertions(+)
>
> diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
> index b72a29c9223c..f334aabdc809 100644
> --- a/tools/perf/Documentation/perf-stat.txt
> +++ b/tools/perf/Documentation/perf-stat.txt
> @@ -162,6 +162,9 @@ null run - Don't start any counters.
>  This can be useful to measure just elapsed wall-clock time - or to assess the
>  raw overhead of perf stat itself, without running any counters.
>
> +--hide-zero-events::
> +Do not show events with a zero count.
> +
>  -v::
>  --verbose::
>          be more verbose (show counter open errors, etc)
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index a04466ea3b0a..8d340c2ae76c 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -2493,6 +2493,8 @@ int cmd_stat(int argc, const char **argv)
>                         "display details about each run (only with -r option)"),
>                 OPT_BOOLEAN('n', "null", &stat_config.null_run,
>                         "null run - dont start any counters"),
> +               OPT_BOOLEAN(0, "hide-zero-events", &stat_config.hide_zero,
> +                       "Do not show events with a zero count"),
>                 OPT_INCR('d', "detailed", &detailed_run,
>                         "detailed run - start a lot of events"),
>                 OPT_BOOLEAN('S', "sync", &sync_run,
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index 0a5750bb59fa..1579e3e2c445 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -907,6 +907,9 @@ static bool should_skip_zero_counter(struct perf_stat_config *config,
>         /* Metric only counts won't be displayed but the metric wants to be computed. */
>         if (config->metric_only)
>                 return false;
> +
> +       if (config->hide_zero && counter->supported)
> +               return true;
>         /*
>          * Skip value 0 when enabling --per-thread globally,
>          * otherwise it will have too many 0 output.
> diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
> index 4bced233d2fc..e3598037a6aa 100644
> --- a/tools/perf/util/stat.h
> +++ b/tools/perf/util/stat.h
> @@ -69,6 +69,7 @@ struct perf_stat_config {
>         bool                     interval_clear;
>         bool                     metric_only;
>         bool                     null_run;
> +       bool                     hide_zero;
>         bool                     ru_display;
>         bool                     big_num;
>         bool                     hybrid_merge;
> --
> 2.54.0
>