linux-kernel - Re: [PATCH 2/2] perf stat: Also hide metric from JSON if units are an empty string

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Message-ID: <ZyGA9cjrtbE_eWik@google.com>
Date: Tue, 29 Oct 2024 17:42:29 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: James Clark <james.clark@...aro.org>, irogers@...gle.com
Cc: linux-perf-users@...r.kernel.org, acme@...nel.org,
	tim.c.chen@...ux.intel.com, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Yicong Yang <yangyicong@...ilicon.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] perf stat: Also hide metric from JSON if units are
 an empty string

Hello,

On Fri, Oct 25, 2024 at 10:03:05AM +0100, James Clark wrote:
> We decided to hide NULL metric units rather than showing it as "(null)",
> but on hybrid systems if the process doesn't hit a PMU you get an empty
> string metric unit instead. To make it consistent also remove empty
> strings.
> 
> 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"}
>  ...

I guess you're talking about "metric-unit", not plain "unit", right?
Then please update the subject line to reduce the config.

Ian, can you please review?

Thanks,
Namhyung

> 
> 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@...aro.org>
> ---
>  tools/perf/util/stat-display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index a5d72f4a515c..9b7fd985a42a 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -506,7 +506,7 @@ static void print_metric_json(struct perf_stat_config *config __maybe_unused,
>  	struct outstate *os = ctx;
>  	FILE *out = os->fh;
>  
> -	if (unit) {
> +	if (unit && strlen(unit)) {
>  		json_out(os, "\"metric-value\" : \"%f\", \"metric-unit\" : \"%s\"", val, unit);
>  		if (thresh != METRIC_THRESHOLD_UNKNOWN) {
>  			json_out(os, "\"metric-threshold\" : \"%s\"",
> -- 
> 2.34.1
>