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Date:   Fri, 13 Aug 2021 22:07:55 +0000
Message-Id: <20210813220754.2104922-1-cjense@google.com>
Mime-Version: 1.0
Subject: [PATCH v2 1/1] perf stat: Add JSON output option.
From:   Claire Jensen <cjense@google.com>
To:     peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
        mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
        jolsa@redhat.com, namhyung@kernel.org, yao.jin@linux.intel.com,
        song@kernel.org, andi@firstfloor.org, adrian.hunter@intel.com,
        kan.liang@linux.intel.com, james.clark@arm.com,
        alexander.antonov@linux.intel.com, changbin.du@intel.com,
        liuqi115@huawei.com, irogers@google.com, eranian@google.com,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        clairej735@gmail.com
Cc:     Claire Jensen <cjense@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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 {
+			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);
+		} 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));
+		}
 
 		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;
-- 
2.33.0.rc1.237.g0d66db33f3-goog