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Subject[PATCH 15/15] perf stat: Tidy up JSON metric-only output when no metrics
Date
It printed empty strings for each metric.  I guess it's needed for CSV
output to match the column number. We could just ignore the empty
metrics in JSON but it ended up with a broken JSON object with a
trailing comma.

So I added a dummy '"metric-value" : "none"' part. To do that, it
needs to pass struct outstate to print_metric_end() to check if any
metric value is printed or not.

Before:
# perf stat -aj --metric-only --per-socket --for-each-cgroup system.slice true
{"socket" : "S0", "cpu-count" : 8, "cgroup" : "system.slice", "" : "", "" : "", "" : "", "" : "", "" : "", "" : "", "" : "", "" : ""}

After:
# perf stat -aj --metric-only --per-socket --for-each-cgroup system.slice true
{"socket" : "S0", "cpu-count" : 8, "cgroup" : "system.slice", "metric-value" : "none"}

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/util/stat-display.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index 7a39a1a7261d..847acdb5dc40 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -532,6 +532,8 @@ static void print_metric_only_json(struct perf_stat_config *config __maybe_unuse
while (isdigit(*ends) || *ends == '.')
ends++;
*ends = 0;
+ if (!unit[0] || !vals[0])
+ return;
fprintf(out, "%s\"%s\" : \"%s\"", os->first ? "" : ", ", unit, vals);
os->first = false;
}
@@ -864,14 +866,19 @@ static void print_metric_begin(struct perf_stat_config *config,
print_cgroup(config, os->cgrp ? : evsel->cgrp);
}

-static void print_metric_end(struct perf_stat_config *config)
+static void print_metric_end(struct perf_stat_config *config, struct outstate *os)
{
+ FILE *output = config->output;
+
if (!config->metric_only)
return;

- if (config->json_output)
- fputc('}', config->output);
- fputc('\n', config->output);
+ if (config->json_output) {
+ if (os->first)
+ fputs("\"metric-value\" : \"none\"", output);
+ fputc('}', output);
+ }
+ fputc('\n', output);
}

static void print_aggr(struct perf_stat_config *config,
@@ -897,7 +904,7 @@ static void print_aggr(struct perf_stat_config *config,

print_counter_aggrdata(config, counter, s, os);
}
- print_metric_end(config);
+ print_metric_end(config, os);
}
}

@@ -929,7 +936,7 @@ static void print_aggr_cgroup(struct perf_stat_config *config,

print_counter_aggrdata(config, counter, s, os);
}
- print_metric_end(config);
+ print_metric_end(config, os);
}
}
}
@@ -985,7 +992,7 @@ static void print_no_aggr_metric(struct perf_stat_config *config,
printout(config, os, uval, run, ena, 1.0, counter_idx);
}
if (!first)
- print_metric_end(config);
+ print_metric_end(config, os);
}
}

@@ -1348,7 +1355,7 @@ static void print_cgroup_counter(struct perf_stat_config *config, struct evlist
evlist__for_each_entry(evlist, counter) {
if (os->cgrp != counter->cgrp) {
if (os->cgrp != NULL)
- print_metric_end(config);
+ print_metric_end(config, os);

os->cgrp = counter->cgrp;
print_metric_begin(config, evlist, os, /*aggr_idx=*/0);
@@ -1357,7 +1364,7 @@ static void print_cgroup_counter(struct perf_stat_config *config, struct evlist
print_counter(config, counter, os);
}
if (os->cgrp)
- print_metric_end(config);
+ print_metric_end(config, os);
}

void evlist__print_counters(struct evlist *evlist, struct perf_stat_config *config,
@@ -1405,7 +1412,7 @@ void evlist__print_counters(struct evlist *evlist, struct perf_stat_config *conf
evlist__for_each_entry(evlist, counter) {
print_counter(config, counter, &os);
}
- print_metric_end(config);
+ print_metric_end(config, &os);
}
break;
case AGGR_NONE:
--
2.38.1.584.g0f3c55d4c2-goog
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