Re: [PATCH v2 2/2] perf stat: Also hide metric-units from JSON when event didn't run

[Ian Rogers]

On Wed, Oct 30, 2024 at 4:40 AM James Clark <james.clark@xxxxxxxxxx> wrote:
>
> We decided to hide NULL metric-units rather than showing it as "(null)"
> when a dependent event for a metric doesn't exist. But on hybrid systems
> if the process doesn't hit a PMU you get an empty string metric unit
> instead. To make it consistent change all empty strings to NULL.
>
> Note that metric-threshold is already hidden in this case without this
> change.
>
> Where a process only runs on cpu_core and never hits cpu_atom:
> Before:
>  $ perf stat -j -- true
>  ...
>  {"counter-value" : "<not counted>", "unit" : "", "event" : "cpu_atom/branch-misses/", "event-runtime" : 0, "pcnt-running" : 0.00, "metric-value" : "0.000000", "metric-unit" : ""}
>  {"counter-value" : "6326.000000", "unit" : "", "event" : "cpu_core/branch-misses/", "event-runtime" : 293786, "pcnt-running" : 100.00, "metric-value" : "3.553394", "metric-unit" : "of all branches", "metric-threshold" : "good"}
>  ...
>
> After:
>  ...
>  {"counter-value" : "<not counted>", "unit" : "", "event" : "cpu_atom/branch-misses/", "event-runtime" : 0, "pcnt-running" : 0.00}
>  {"counter-value" : "5778.000000", "unit" : "", "event" : "cpu_core/branch-misses/", "event-runtime" : 282240, "pcnt-running" : 100.00, "metric-value" : "3.226797", "metric-unit" : "of all branches", "metric-threshold" : "good"}
>  ...
>
> Signed-off-by: James Clark <james.clark@xxxxxxxxxx>

Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

> ---
>  tools/perf/util/stat-display.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index a5d72f4a515c..0e16eecfbad8 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -854,7 +854,8 @@ static void printout(struct perf_stat_config *config, struct outstate *os,
>
>         if (run == 0 || ena == 0 || counter->counts->scaled == -1) {
>                 if (config->metric_only) {
> -                       pm(config, os, METRIC_THRESHOLD_UNKNOWN, "", "", 0);
> +                       pm(config, os, METRIC_THRESHOLD_UNKNOWN, /*format=*/NULL,
> +                          /*unit=*/NULL, /*val=*/0);
>                         return;
>                 }
>
> @@ -909,7 +910,7 @@ static void printout(struct perf_stat_config *config, struct outstate *os,
>                         perf_stat__print_shadow_stats(config, counter, uval, aggr_idx,
>                                                       &out, &config->metric_events);
>         } else {
> -               pm(config, os, METRIC_THRESHOLD_UNKNOWN, /*format=*/NULL, /*unit=*/"", /*val=*/0);
> +               pm(config, os, METRIC_THRESHOLD_UNKNOWN, /*format=*/NULL, /*unit=*/NULL, /*val=*/0);
>         }
>
>         if (!config->metric_only) {
> --
> 2.34.1
>