Re: [PATCH v2 1/1] perf stat: Add JSON output option.

kajoljain
2021-08-14T13:27:10Z

On 8/14/21 3:37 AM, Claire Jensen wrote:
> CSV output is tricky to format and column layout changes are susceptible
> to breaking parsers. New JSON-formatted output has variable names to
> identify fields that are consistent and informative, making
> the output parseable.
>
> CSV output example:
>
> 1.20,msec,task-clock:u,1204272,100.00,0.697,CPUs utilized
> 0,,context-switches:u,1204272,100.00,0.000,/sec
> 0,,cpu-migrations:u,1204272,100.00,0.000,/sec
> 70,,page-faults:u,1204272,100.00,58.126,K/sec
>
> JSON output example:
>
> {"counter-value" : "3805.723968", "unit" : "msec", "event" :
> "cpu-clock", "event-runtime" : 3805731510100.00, "pcnt-running"
> : 100.00, "metric-value" : 4.007571, "metric-unit" : "CPUs utilized"}
> {"counter-value" : "6166.000000", "unit" : "", "event" :
> "context-switches", "event-runtime" : 3805723045100.00, "pcnt-running"
> : 100.00, "metric-value" : 1.620191, "metric-unit" : "K/sec"}
> {"counter-value" : "466.000000", "unit" : "", "event" :
> "cpu-migrations", "event-runtime" : 3805727613100.00, "pcnt-running"
> : 100.00, "metric-value" : 122.447136, "metric-unit" : "/sec"}
> {"counter-value" : "208.000000", "unit" : "", "event" :
> "page-faults", "event-runtime" : 3805726799100.00, "pcnt-running"
> : 100.00, "metric-value" : 54.654516, "metric-unit" : "/sec"}
>
> Also added documentation for JSON option.
>
> Version 2 includes change to SPDX-License-Identifier location, moving it
> to line 3 due to an error when the test name was not found on
> line 2. Additionally, testing was separated from the output patch.
>
> Signed-off-by: Claire Jensen <cjense@google.com>
> ---
> tools/perf/Documentation/perf-stat.txt | 21 ++
> tools/perf/builtin-stat.c | 2 +
> tools/perf/util/stat-display.c | 383 ++++++++++++++++++-------
> tools/perf/util/stat-shadow.c | 5 +-
> tools/perf/util/stat.h | 1 +
> 5 files changed, 310 insertions(+), 102 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
> index 45c2467e4eb2..80ae3802a904 100644
> --- a/tools/perf/Documentation/perf-stat.txt
> +++ b/tools/perf/Documentation/perf-stat.txt
> @@ -554,6 +554,27 @@ Additional metrics may be printed with all earlier fields being empty.
>
> include::intel-hybrid.txt[]
>
> +JSON FORMAT
> +-----------
> +
> +With -j, perf stat is able to print out a JSON format output
> +that can be used for parsing.
> +
> +- timestamp : optional usec time stamp in fractions of second (with -I)
> +- optional aggregate options:
> + - core : core identifier (with --per-core)
> + - die : die identifier (with --per-die)
> + - socket : socket identifier (with --per-socket)
> + - node : node identifier (with --per-node)
> + - thread : thread identifier (with --per-thread)
> +- counter-value : counter value
> +- unit : unit of the counter value or empty
> +- event : event name
> +- variance : optional variance if multiple values are collected (with -r)
> +- runtime : run time of counter
> +- metric-value : optional metric value
> +- metric-unit : optional unit of metric
> +
> SEE ALSO
> --------
> linkperf:perf-top[1], linkperf:perf-list[1]
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 634375937db9..71b8418a2a06 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -1218,6 +1218,8 @@ static struct option stat_options[] = {
> OPT_BOOLEAN(0, "no-merge", &stat_config.no_merge, "Do not merge identical named events"),
> OPT_STRING('x', "field-separator", &stat_config.csv_sep, "separator",
> "print counts with custom separator"),
> + OPT_BOOLEAN('j', "json-output", &stat_config.json_output,
> + "print counts in JSON format"),
> OPT_CALLBACK('G', "cgroup", &evsel_list, "name",
> "monitor event in cgroup name only", parse_stat_cgroups),
> OPT_STRING(0, "for-each-cgroup", &stat_config.cgroup_list, "name",
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index 588601000f3f..59de118352f3 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -27,23 +27,26 @@
> static void print_running(struct perf_stat_config *config,
> u64 run, u64 ena)
> {
> - if (config->csv_output) {
> - fprintf(config->output, "%s%" PRIu64 "%s%.2f",
> - config->csv_sep,
> - run,
> - config->csv_sep,
> - ena ? 100.0 * run / ena : 100.0);
> - } else if (run != ena) {
> + double enabled_percent = 100;
> + if (run != ena)
> + enabled_percent = 100 * run / ena;
> + if (config->json_output)
> + fprintf(config->output, "\"event-runtime\" : %lu, \"pcnt-running\" : %.2f, ",
> + run, enabled_percent);
> + else if (config->csv_output)
> + fprintf(config->output, "%s%" PRIu64 "%s%.2f", config->csv_sep,
> + run, config->csv_sep, enabled_percent);
> + else if (run != ena)
> fprintf(config->output, " (%.2f%%)", 100.0 * run / ena);
> - }
> }
>
> static void print_noise_pct(struct perf_stat_config *config,
> double total, double avg)
> {
> double pct = rel_stddev_stats(total, avg);
> -
> - if (config->csv_output)
> + if (config->json_output)
> + fprintf(config->output, "\"variance\" : %.2f, ", pct);
> + else if (config->csv_output)
> fprintf(config->output, "%s%.2f%%", config->csv_sep, pct);
> else if (pct)
> fprintf(config->output, " ( +-%6.2f%% )", pct);
> @@ -63,9 +66,14 @@ static void print_noise(struct perf_stat_config *config,
>
> static void print_cgroup(struct perf_stat_config *config, struct evsel *evsel)
> {
> - if (nr_cgroups) {
> + if (config->json_output && nr_cgroups) {
> const char *cgrp_name = evsel->cgrp ? evsel->cgrp->name : "";
> + fprintf(config->output, "\"cgroup\" : \"%s\", ", cgrp_name);
> + } else {
> + if (nr_cgroups) {
> + const char *cgrp_name = evsel->cgrp ? evsel->cgrp->name : "";
> fprintf(config->output, "%s%s", config->csv_sep, cgrp_name);
> + }
> }
> }
>
> @@ -73,8 +81,18 @@ static void print_cgroup(struct perf_stat_config *config, struct evsel *evsel)
> static void aggr_printout(struct perf_stat_config *config,
> struct evsel *evsel, struct aggr_cpu_id id, int nr)
> {
> + if (config->json_output && !config->interval)
> + fprintf(config->output, "{");
> +
> switch (config->aggr_mode) {
> case AGGR_CORE:
> + if (config->json_output) {
> + fprintf(config->output, "\"core\" : \"S%d-D%d-C%d\", \"cpu\" : %d, ",
> + id.socket,
> + id.die,
> + id.core,
> + nr);
> + } else {
> fprintf(config->output, "S%d-D%d-C%*d%s%*d%s",
> id.socket,
> id.die,
> @@ -84,56 +102,95 @@ static void aggr_printout(struct perf_stat_config *config,
> config->csv_output ? 0 : 4,
> nr,
> config->csv_sep);
> + }
> break;
> case AGGR_DIE:
> - fprintf(config->output, "S%d-D%*d%s%*d%s",
> - id.socket,
> - config->csv_output ? 0 : -8,
> - id.die,
> - config->csv_sep,
> - config->csv_output ? 0 : 4,
> - nr,
> - config->csv_sep);
> + if (config->json_output) {
> + fprintf(config->output, "\"die\" : \"S%d-D%d\", \"cpu\" : %d, ",
> + id.socket,
> + id.die,
> + nr);
> + } else {

Hi Claire,
This section of if-else have indentation issue.

> + fprintf(config->output, "S%d-D%*d%s%*d%s",
> + id.socket,
> + config->csv_output ? 0 : -8,
> + id.die,
> + config->csv_sep,
> + config->csv_output ? 0 : 4,
> + nr,
> + config->csv_sep);
> + }
> break;
> case AGGR_SOCKET:
> - fprintf(config->output, "S%*d%s%*d%s",
> - config->csv_output ? 0 : -5,
> - id.socket,
> - config->csv_sep,
> - config->csv_output ? 0 : 4,
> - nr,
> - config->csv_sep);
> + if (config->json_output) {
> + fprintf(config->output, "\"socket\" : \"S%d\", \"number\" : %d, ",
> + id.socket,
> + nr);

Similarly here. You can get all these format error by running scripts/checkpatch.pl script.

> + } else {
> + fprintf(config->output, "S%*d%s%*d%s",
> + config->csv_output ? 0 : -5,
> + id.socket,
> + config->csv_sep,
> + config->csv_output ? 0 : 4,
> + nr,
> + config->csv_sep);
> + }
> break;
> case AGGR_NODE:
> - fprintf(config->output, "N%*d%s%*d%s",
> - config->csv_output ? 0 : -5,
> - id.node,
> - config->csv_sep,
> - config->csv_output ? 0 : 4,
> - nr,
> - config->csv_sep);
> + if (config->json_output) {
> + fprintf(config->output, "\"node\" : \"N%d\", \"cpu\" : %d, ",
> + id.node,
> + nr);
> + } else {
> + fprintf(config->output, "N%*d%s%*d%s",
> + config->csv_output ? 0 : -5,
> + id.node,
> + config->csv_sep,
> + config->csv_output ? 0 : 4,
> + nr,
> + config->csv_sep);
> + }
> break;
> case AGGR_NONE:
> - if (evsel->percore && !config->percore_show_thread) {
> - fprintf(config->output, "S%d-D%d-C%*d%s",
> - id.socket,
> - id.die,
> - config->csv_output ? 0 : -3,
> - id.core, config->csv_sep);
> + if (config->json_output) {
> + if (evsel->percore && !config->percore_show_thread) {
> + fprintf(config->output, "\"core\" : \"S%d-D%d-C%d\"",
> + id.socket,
> + id.die,
> + id.core);
> + } else if (id.core > -1) {
> + fprintf(config->output, "\"cpu\" : \"%d\", ",
> + evsel__cpus(evsel)->map[id.core]);
> + }
> + } else {
> + if (evsel->percore && !config->percore_show_thread) {
> + fprintf(config->output, "S%d-D%d-C%*d%s",
> + id.socket,
> + id.die,
> + config->csv_output ? 0 : -3,
> + id.core, config->csv_sep);
> } else if (id.core > -1) {
> fprintf(config->output, "CPU%*d%s",
> config->csv_output ? 0 : -7,
> evsel__cpus(evsel)->map[id.core],
> config->csv_sep);
> - }
> + }
> + }
> +
> break;
> case AGGR_THREAD:
> - fprintf(config->output, "%*s-%*d%s",
> - config->csv_output ? 0 : 16,
> - perf_thread_map__comm(evsel->core.threads, id.thread),
> - config->csv_output ? 0 : -8,
> - perf_thread_map__pid(evsel->core.threads, id.thread),
> - config->csv_sep);
> + if (config->json_output) {
> + fprintf(config->output, "\"thread\" : \"%s-%d\", ",
> + perf_thread_map__comm(evsel->core.threads, id.thread),
> + perf_thread_map__pid(evsel->core.threads, id.thread));
> + } else {
> + fprintf(config->output, "%*s-%*d%s",
> + config->csv_output ? 0 : 16,
> + perf_thread_map__comm(evsel->core.threads, id.thread),
> + config->csv_output ? 0 : -8,
> + perf_thread_map__pid(evsel->core.threads, id.thread),
> + config->csv_sep);
> + }
> break;
> case AGGR_GLOBAL:
> case AGGR_UNSET:
> @@ -184,20 +241,54 @@ static void print_metric_std(struct perf_stat_config *config,
>
> os->newline = false;
>
> + if (unit == NULL || fmt == NULL) {
> + fprintf(out, "%-*s", METRIC_LEN, "");
> + return;
> + }
> + if (newline)
> + do_new_line_std(config, os);
> + n = fprintf(out, " # ");
> + if (color)
> + n += color_fprintf(out, color, fmt, val);
> + else
> + n += fprintf(out, fmt, val);
> + fprintf(out, " %-*s", METRIC_LEN - n - 1, unit);
> +}
> +
> +static void print_metric_csv(struct perf_stat_config *config __maybe_unused,
> + void *ctx,
> + const char *color __maybe_unused,
> + const char *fmt, const char *unit, double val)
> +{
> + struct outstate *os = ctx;
> + FILE *out = os->fh;
> + char buf[64], *vals, *ends;
> +
> if (unit == NULL || fmt == NULL) {
> - fprintf(out, "%-*s", METRIC_LEN, "");
> + fprintf(out, "%s%s", config->csv_sep, config->csv_sep);
> return;
> }
> + snprintf(buf, sizeof(buf), fmt, val);
> + ends = vals = skip_spaces(buf);
> + while (isdigit(*ends) || *ends == '.')
> + ends++;
> + *ends = 0;
> + fprintf(out, "%s%s%s%s", config->csv_sep, vals,
> + config->csv_sep, skip_spaces(unit));
> +}
>
> - if (newline)
> - do_new_line_std(config, os);
> +static void print_metric_json(struct perf_stat_config *config __maybe_unused,
> + void *ctx,
> + const char *color __maybe_unused,
> + const char *fmt, const char *unit, double val)
> +{
> + struct outstate *os = ctx;
> + FILE *out = os->fh;
>
> - n = fprintf(out, " # ");
> - if (color)
> - n += color_fprintf(out, color, fmt, val);
> - else
> - n += fprintf(out, fmt, val);
> - fprintf(out, " %-*s", METRIC_LEN - n - 1, unit);
> + fprintf(out, "\"metric-value\" : %f, ", val);
> + fprintf(out, "\"metric-unit\" : \"%s\"", unit);
> + if (!config->metric_only)
> + fprintf(out, "}");
> }
>
> static void new_line_csv(struct perf_stat_config *config, void *ctx)
> @@ -213,25 +304,14 @@ static void new_line_csv(struct perf_stat_config *config, void *ctx)
> fputs(config->csv_sep, os->fh);
> }
>
> -static void print_metric_csv(struct perf_stat_config *config __maybe_unused,
> - void *ctx,
> - const char *color __maybe_unused,
> - const char *fmt, const char *unit, double val)
> +static void new_line_json(struct perf_stat_config *config, void *ctx)
> {
> struct outstate *os = ctx;
> - FILE *out = os->fh;
> - char buf[64], *vals, *ends;
>
> - if (unit == NULL || fmt == NULL) {
> - fprintf(out, "%s%s", config->csv_sep, config->csv_sep);
> - return;
> - }
> - snprintf(buf, sizeof(buf), fmt, val);
> - ends = vals = skip_spaces(buf);
> - while (isdigit(*ends) || *ends == '.')
> - ends++;
> - *ends = 0;
> - fprintf(out, "%s%s%s%s", config->csv_sep, vals, config->csv_sep, skip_spaces(unit));
> + fputc('\n', os->fh);
> + if (os->prefix)
> + fprintf(os->fh, "%s", os->prefix);
> + aggr_printout(config, os->evsel, os->id, os->nr);
> }
>
> /* Filter out some columns that don't work well in metrics only mode */
> @@ -292,7 +372,7 @@ static void print_metric_only_csv(struct perf_stat_config *config __maybe_unused
> if (!valid_only_metric(unit))
> return;
> unit = fixunit(tbuf, os->evsel, unit);
> - snprintf(buf, sizeof buf, fmt, val);
> + snprintf(buf, sizeof(buf), fmt, val);
> ends = vals = skip_spaces(buf);
> while (isdigit(*ends) || *ends == '.')
> ends++;
> @@ -300,6 +380,27 @@ static void print_metric_only_csv(struct perf_stat_config *config __maybe_unused
> fprintf(out, "%s%s", vals, config->csv_sep);
> }
>
> +static void print_metric_only_json(struct perf_stat_config *config __maybe_unused,
> + void *ctx, const char *color __maybe_unused,
> + const char *fmt,
> + const char *unit, double val)
> +{
> + struct outstate *os = ctx;
> + FILE *out = os->fh;
> + char buf[64], *vals, *ends;
> + char tbuf[1024];
> +
> + if (!valid_only_metric(unit))
> + return;
> + unit = fixunit(tbuf, os->evsel, unit);
> + snprintf(buf, sizeof(buf), fmt, val);
> + ends = vals = skip_spaces(buf);
> + while (isdigit(*ends) || *ends == '.')
> + ends++;
> + *ends = 0;
> + fprintf(out, "{\"metric-value\" : \"%s\"}", vals);
> +}
> +
> static void new_line_metric(struct perf_stat_config *config __maybe_unused,
> void *ctx __maybe_unused)
> {
> @@ -318,10 +419,13 @@ static void print_metric_header(struct perf_stat_config *config,
> os->evsel->priv != os->evsel->evlist->selected->priv)
> return;
>
> - if (!valid_only_metric(unit))
> + if (!valid_only_metric(unit) && !config->json_output)
> return;
> unit = fixunit(tbuf, os->evsel, unit);
> - if (config->csv_output)
> +
> + if (config->json_output)
> + fprintf(os->fh, "\"unit\" : \"%s\"", unit);
> + else if (config->csv_output)
> fprintf(os->fh, "%s%s", unit, config->csv_sep);
> else
> fprintf(os->fh, "%*s ", config->metric_only_len, unit);
> @@ -369,14 +473,27 @@ static void abs_printout(struct perf_stat_config *config,
>
> aggr_printout(config, evsel, id, nr);
>
> - fprintf(output, fmt, avg, config->csv_sep);
> + if (config->json_output)
> + fprintf(output, "\"counter-value\" : \"%f\", ", avg);
> + else
> + fprintf(output, fmt, avg, config->csv_sep);
>
> - if (evsel->unit)
> - fprintf(output, "%-*s%s",
> - config->csv_output ? 0 : config->unit_width,
> - evsel->unit, config->csv_sep);
> + if (config->json_output) {
> + if (evsel->unit) {
> + fprintf(output, "\"unit\" : \"%s\", ",
> + evsel->unit);
> + }
> + } else {
> + if (evsel->unit)
> + fprintf(output, "%-*s%s",
> + config->csv_output ? 0 : config->unit_width,
> + evsel->unit, config->csv_sep);
> + }
>
> - fprintf(output, "%-*s", config->csv_output ? 0 : 25, evsel__name(evsel));
> + if (config->json_output)
> + fprintf(output, "\"event\" : \"%s\", ", evsel__name(evsel));
> + else
> + fprintf(output, "%-*s", config->csv_output ? 0 : 25, evsel__name(evsel));
>
> print_cgroup(config, evsel);
> }
> @@ -425,6 +542,8 @@ static void printout(struct perf_stat_config *config, struct aggr_cpu_id id, int
> nl = new_line_metric;
> if (config->csv_output)
> pm = print_metric_only_csv;
> + else if (config->json_output)
> + pm = print_metric_only_json;
> else
> pm = print_metric_only;
> } else
> @@ -448,6 +567,24 @@ static void printout(struct perf_stat_config *config, struct aggr_cpu_id id, int
> os.nfields++;
> }
>
> + if (config->json_output && !config->metric_only) {
> + static int aggr_fields[] = {
> + [AGGR_GLOBAL] = 0,
> + [AGGR_THREAD] = 1,
> + [AGGR_NONE] = 1,
> + [AGGR_SOCKET] = 2,
> + [AGGR_DIE] = 2,
> + [AGGR_CORE] = 2,
> + };
> +
> + pm = print_metric_json;
> + nl = new_line_json;
> + os.nfields = 3;
> + os.nfields += aggr_fields[config->aggr_mode];
> + if (counter->cgrp)
> + os.nfields++;
> + }
> +
> if (!config->no_csv_summary && config->csv_output &&
> config->summary && !config->interval) {
> fprintf(config->output, "%16s%s", "summary", config->csv_sep);
> @@ -460,10 +597,15 @@ static void printout(struct perf_stat_config *config, struct aggr_cpu_id id, int
> }
> aggr_printout(config, counter, id, nr);
>
> - fprintf(config->output, "%*s%s",
> - config->csv_output ? 0 : 18,
> - counter->supported ? CNTR_NOT_COUNTED : CNTR_NOT_SUPPORTED,
> - config->csv_sep);
> + if (config->json_output) {
> + fprintf(config->output, "\"counter-value\" : \"%s\", ",
> + counter->supported ? CNTR_NOT_COUNTED : CNTR_NOT_SUPPORTED);
> + } else {
> + fprintf(config->output, "%*s%s",
> + config->csv_output ? 0 : 18,
> + counter->supported ? CNTR_NOT_COUNTED : CNTR_NOT_SUPPORTED,
> + config->csv_sep);
> + }
>
> if (counter->supported) {
> if (!evlist__has_hybrid(counter->evlist)) {
> @@ -473,21 +615,32 @@ static void printout(struct perf_stat_config *config, struct aggr_cpu_id id, int
> }
> }
>
> - fprintf(config->output, "%-*s%s",
> - config->csv_output ? 0 : config->unit_width,
> - counter->unit, config->csv_sep);
> + if (config->json_output) {
> + fprintf(config->output, "\"unit\" : \"%s\", ", counter->unit);
> + } else {
> + fprintf(config->output, "%-*s%s",
> + config->csv_output ? 0 : config->unit_width,
> + counter->unit, config->csv_sep);
> + }
>
> - fprintf(config->output, "%*s",
> - config->csv_output ? 0 : -25, evsel__name(counter));
> + if (config->json_output) {
> + fprintf(config->output, "\"event\" : \"%s\", ",
> + evsel__name(counter));
> + } else {
> + fprintf(config->output, "%*s",
> + config->csv_output ? 0 : -25, evsel__name(counter));
> + }
>

Here in multiple places we have if condition check for (config->json_output), is it better to merge all these in single
if condition?

Thanks,
Kajol Jain

> print_cgroup(config, counter);
>
> - if (!config->csv_output)
> + if (!config->csv_output && !config->json_output)
> pm(config, &os, NULL, NULL, "", 0);
> print_noise(config, counter, noise);
> print_running(config, run, ena);
> if (config->csv_output)
> pm(config, &os, NULL, NULL, "", 0);
> + else if (config->json_output)
> + pm(config, &os, NULL, NULL, "", 0);
> return;
> }
>
> @@ -502,12 +655,15 @@ static void printout(struct perf_stat_config *config, struct aggr_cpu_id id, int
> if (config->csv_output && !config->metric_only) {
> print_noise(config, counter, noise);
> print_running(config, run, ena);
> + } else if (config->json_output && !config->metric_only) {
> + print_noise(config, counter, noise);
> + print_running(config, run, ena);
> }
>
> perf_stat__print_shadow_stats(config, counter, uval,
> first_shadow_cpu(config, counter, id),
> &out, &config->metric_events, st);
> - if (!config->csv_output && !config->metric_only) {
> + if (!config->csv_output && !config->metric_only && !config->json_output) {
> print_noise(config, counter, noise);
> print_running(config, run, ena);
> }
> @@ -866,7 +1022,8 @@ static void print_counter_aggr(struct perf_stat_config *config,
> fprintf(output, "%s", prefix);
>
> uval = cd.avg * counter->scale;
> - printout(config, cpu_map__empty_aggr_cpu_id(), 0, counter, uval, prefix, cd.avg_running,
> + printout(config, cpu_map__empty_aggr_cpu_id(), 0, counter,
> + uval, prefix, cd.avg_running,
> cd.avg_enabled, cd.avg, &rt_stat);
> if (!metric_only)
> fprintf(output, "\n");
> @@ -981,8 +1138,12 @@ static void print_metric_headers(struct perf_stat_config *config,
> struct outstate os = {
> .fh = config->output
> };
> + bool first = true;
> +
> + if (config->json_output && !config->interval)
> + fprintf(config->output, "{");
>
> - if (prefix)
> + if (prefix && !config->json_output)
> fprintf(config->output, "%s", prefix);
>
> if (!config->csv_output && !no_indent)
> @@ -1002,6 +1163,9 @@ static void print_metric_headers(struct perf_stat_config *config,
> os.evsel = counter;
> out.ctx = &os;
> out.print_metric = print_metric_header;
> + if (!first && config->json_output)
> + fprintf(config->output, ", ");
> + first = false;
> out.new_line = new_line_metric;
> out.force_header = true;
> perf_stat__print_shadow_stats(config, counter, 0,
> @@ -1010,6 +1174,8 @@ static void print_metric_headers(struct perf_stat_config *config,
> &config->metric_events,
> &rt_stat);
> }
> + if (config->json_output)
> + fprintf(config->output, "}");
> fputc('\n', config->output);
> }
>
> @@ -1025,10 +1191,18 @@ static void print_interval(struct perf_stat_config *config,
> if (config->interval_clear)
> puts(CONSOLE_CLEAR);
>
> - if (!config->iostat_run)
> - sprintf(prefix, "%6lu.%09lu%s", (unsigned long) ts->tv_sec, ts->tv_nsec, config->csv_sep);
> -
> - if ((num_print_interval == 0 && !config->csv_output) || config->interval_clear) {
> + if (!config->iostat_run && !config->json_output)
> + sprintf(prefix, "%6lu.%09lu%s", (unsigned long) ts->tv_sec,
> + ts->tv_nsec, config->csv_sep);
> + if (!config->iostat_run && config->json_output && !config->metric_only)
> + sprintf(prefix, "{\"interval\" : %lu.%09lu, ", (unsigned long)
> + ts->tv_sec, ts->tv_nsec);
> + if (!config->iostat_run && config->json_output && config->metric_only)
> + sprintf(prefix, "{\"interval\" : %lu.%09lu}", (unsigned long)
> + ts->tv_sec, ts->tv_nsec);
> +
> + if ((num_print_interval == 0 && !config->csv_output && !config->json_output)
> + || config->interval_clear) {
> switch (config->aggr_mode) {
> case AGGR_NODE:
> fprintf(output, "# time node cpus");
> @@ -1072,8 +1246,14 @@ static void print_interval(struct perf_stat_config *config,
> }
> }
>
> - if ((num_print_interval == 0 || config->interval_clear) && metric_only)
> + if ((num_print_interval == 0 || config->interval_clear)
> + && metric_only && !config->json_output)
> + print_metric_headers(config, evlist, " ", true);
> + if ((num_print_interval == 0 || config->interval_clear)
> + && metric_only && config->json_output) {
> + fprintf(output, "{");
> print_metric_headers(config, evlist, " ", true);
> + }
> if (++num_print_interval == 25)
> num_print_interval = 0;
> }
> @@ -1087,7 +1267,7 @@ static void print_header(struct perf_stat_config *config,
>
> fflush(stdout);
>
> - if (!config->csv_output) {
> + if (!config->csv_output && !config->json_output) {
> fprintf(output, "\n");
> fprintf(output, " Performance counter stats for ");
> if (_target->bpf_str)
> @@ -1276,6 +1456,9 @@ void evlist__print_counters(struct evlist *evlist, struct perf_stat_config *conf
> num_print_iv = 0;
> if (config->aggr_mode == AGGR_GLOBAL && prefix && !config->iostat_run)
> fprintf(config->output, "%s", prefix);
> +
> + if (config->json_output && !config->metric_only)
> + fprintf(config->output, "}");
> }
>
> switch (config->aggr_mode) {
> @@ -1319,7 +1502,7 @@ void evlist__print_counters(struct evlist *evlist, struct perf_stat_config *conf
> break;
> }
>
> - if (!interval && !config->csv_output)
> + if (!interval && !config->csv_output && !config->json_output)
> print_footer(config);
>
> fflush(config->output);
> diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
> index 34a7f5c1fff7..156302f8eaf6 100644
> --- a/tools/perf/util/stat-shadow.c
> +++ b/tools/perf/util/stat-shadow.c
> @@ -981,8 +981,9 @@ void perf_stat__print_shadow_stats(struct perf_stat_config *config,
> total = max(total, runtime_stat_avg(st,
> STAT_STALLED_CYCLES_BACK,
> cpu, &rsd));
> -
> - if (total && avg) {
> + // TODO: Refactor code to avoid errors in JSON output.
> + // !config->json_output is temporary workaround for JSON linter.
> + if (total && avg && !config->json_output) {
> out->new_line(config, ctxp);
> ratio = total / avg;
> print_metric(config, ctxp, NULL, "%7.2f ",
> diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
> index 32c8527de347..2bde525e7630 100644
> --- a/tools/perf/util/stat.h
> +++ b/tools/perf/util/stat.h
> @@ -117,6 +117,7 @@ struct perf_stat_config {
> bool no_inherit;
> bool identifier;
> bool csv_output;
> + bool json_output;
> bool interval_clear;
> bool metric_only;
> bool null_run;
>