[PATCH 0/2] JSON output for perf stat

[PATCH 0/2] JSON output for perf stat

[Ian Rogers]

Parsing the CSV or text output of perf stat can be problematic when
new output is added (columns in CSV format). JSON names values and
simplifies the job of parsing. Add a JSON output option to perf-stat
then add unit test that parses and validates the output.

This is a resend of two v2 patches:
https://lore.kernel.org/lkml/20210813220754.2104922-1-cjense@google.com/
https://lore.kernel.org/lkml/20210813220936.2105426-1-cjense@google.com/
with a few formatting changes and improvements to the linter.


Claire Jensen (2):
  perf stat: Add JSON output option
  perf test: Json format checking

 tools/perf/Documentation/perf-stat.txt        |  21 +
 tools/perf/builtin-stat.c                     |   2 +
 .../tests/shell/lib/perf_json_output_lint.py  |  90 +++++
 tools/perf/tests/shell/stat+json_output.sh    | 141 +++++++
 tools/perf/util/stat-display.c                | 365 +++++++++++++-----
 tools/perf/util/stat.h                        |   1 +
 6 files changed, 534 insertions(+), 86 deletions(-)
 create mode 100644 tools/perf/tests/shell/lib/perf_json_output_lint.py
 create mode 100755 tools/perf/tests/shell/stat+json_output.sh

-- 
2.36.0.550.gb090851708-goog

[PATCH 1/2] perf stat: Add JSON output option

[Ian Rogers]

From: Claire Jensen <cjense@google.com>

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.

Signed-off-by: Claire Jensen <cjense@google.com>
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/Documentation/perf-stat.txt |  21 ++
 tools/perf/builtin-stat.c              |   2 +
 tools/perf/util/stat-display.c         | 365 +++++++++++++++++++------
 tools/perf/util/stat.h                 |   1 +
 4 files changed, 303 insertions(+), 86 deletions(-)

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 8d1cde00b8d6..f9cdfd912b05 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -570,6 +570,27 @@ 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 1b96636df01e..0855f763d17d 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -1262,6 +1262,8 @@ static struct option stat_options[] = {
 		    "Merge identical named hybrid 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 98669ca5a86b..1e93094146cd 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -28,15 +28,21 @@
 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,
@@ -44,7 +50,9 @@ static void print_noise_pct(struct perf_stat_config *config,
 {
 	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);
@@ -66,7 +74,11 @@ static void print_cgroup(struct perf_stat_config *config, struct evsel *evsel)
 {
 	if (nr_cgroups) {
 		const char *cgrp_name = evsel->cgrp ? evsel->cgrp->name  : "";
-		fprintf(config->output, "%s%s", config->csv_sep, cgrp_name);
+
+		if (config->json_output)
+			fprintf(config->output, "\"cgroup\" : \"%s\", ", cgrp_name);
+		else
+			fprintf(config->output, "%s%s", config->csv_sep, cgrp_name);
 	}
 }
 
@@ -74,66 +86,119 @@ 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:
-		fprintf(config->output, "S%d-D%d-C%*d%s%*d%s",
-			id.socket,
-			id.die,
-			config->csv_output ? 0 : -8,
-			id.core,
-			config->csv_sep,
-			config->csv_output ? 0 : 4,
-			nr,
-			config->csv_sep);
+		if (config->json_output) {
+			fprintf(config->output,
+				"\"core\" : \"S%d-D%d-C%d\", \"aggregate-number\" : %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,
+				config->csv_output ? 0 : -8,
+				id.core,
+				config->csv_sep,
+				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\", \"aggregate-number\" : %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);
-			break;
+		if (config->json_output) {
+			fprintf(config->output,
+				"\"socket\" : \"S%d\", \"aggregate-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);
-			break;
+		if (config->json_output) {
+			fprintf(config->output, "\"node\" : \"N%d\", \"aggregate-number\" : %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);
-		} else if (id.cpu.cpu > -1) {
-			fprintf(config->output, "CPU%*d%s",
-				config->csv_output ? 0 : -7,
-				id.cpu.cpu, 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\", ",
+					id.cpu.cpu);
+			}
+		} 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,
+					id.cpu.cpu, 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:
@@ -234,6 +299,31 @@ static void print_metric_csv(struct perf_stat_config *config __maybe_unused,
 	fprintf(out, "%s%s%s%s", config->csv_sep, vals, config->csv_sep, skip_spaces(unit));
 }
 
+static void print_metric_json(struct perf_stat_config *config __maybe_unused,
+			     void *ctx,
+			     const char *color __maybe_unused,
+			     const char *fmt __maybe_unused,
+			     const char *unit, double val)
+{
+	struct outstate *os = ctx;
+	FILE *out = os->fh;
+
+	fprintf(out, "\"metric-value\" : %f, ", val);
+	fprintf(out, "\"metric-unit\" : \"%s\"", unit);
+	if (!config->metric_only)
+		fprintf(out, "}");
+}
+
+static void new_line_json(struct perf_stat_config *config, void *ctx)
+{
+	struct outstate *os = ctx;
+
+	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 */
 
 static bool valid_only_metric(const char *unit)
@@ -300,6 +390,27 @@ 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 +429,13 @@ 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);
@@ -367,14 +481,28 @@ 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 (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);
+	}
 
-	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);
 }
@@ -423,6 +551,8 @@ 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
@@ -446,6 +576,24 @@ static void printout(struct perf_stat_config *config, struct aggr_cpu_id id, int
 			os.nfields++;
 	}
 
+	if (config->json_output && !config->metric_only) {
+		static const 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);
@@ -458,10 +606,15 @@ 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)) {
@@ -471,21 +624,32 @@ 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;
 	}
 
@@ -500,12 +664,15 @@ 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_map_idx(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);
 	}
@@ -1002,8 +1169,12 @@ static void print_metric_headers(struct perf_stat_config *config,
 	struct outstate os = {
 		.fh = config->output
 	};
+	bool first = true;
 
-	if (prefix)
+		if (config->json_output && !config->interval)
+			fprintf(config->output, "{");
+
+	if (prefix && !config->json_output)
 		fprintf(config->output, "%s", prefix);
 
 	if (!config->csv_output && !no_indent)
@@ -1023,6 +1194,9 @@ 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,
@@ -1031,6 +1205,8 @@ 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);
 }
 
@@ -1046,10 +1222,18 @@ 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");
@@ -1093,8 +1277,14 @@ 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;
 }
@@ -1108,7 +1298,7 @@ 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)
@@ -1301,6 +1491,9 @@ 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) {
@@ -1344,7 +1537,7 @@ 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.h b/tools/perf/util/stat.h
index b5aeb8e6d34b..09120337cdba 100644
--- a/tools/perf/util/stat.h
+++ b/tools/perf/util/stat.h
@@ -121,6 +121,7 @@ struct perf_stat_config {
 	bool			 no_inherit;
 	bool			 identifier;
 	bool			 csv_output;
+	bool			 json_output;
 	bool			 interval_clear;
 	bool			 metric_only;
 	bool			 null_run;
-- 
2.36.0.550.gb090851708-goog

[PATCH 2/2] perf test: Json format checking

[Ian Rogers]

From: Claire Jensen <cjense@google.com>

Add field checking tests for perf stat JSON output.
Sanity checks the expected number of fields are present, that the
expected keys are present and they have the correct values.

Signed-off-by: Claire Jensen <cjense@google.com>
Signed-off-by: Ian Rogers <irogers@google.com>
---
 .../tests/shell/lib/perf_json_output_lint.py  |  90 +++++++++++
 tools/perf/tests/shell/stat+json_output.sh    | 141 ++++++++++++++++++
 2 files changed, 231 insertions(+)
 create mode 100644 tools/perf/tests/shell/lib/perf_json_output_lint.py
 create mode 100755 tools/perf/tests/shell/stat+json_output.sh

diff --git a/tools/perf/tests/shell/lib/perf_json_output_lint.py b/tools/perf/tests/shell/lib/perf_json_output_lint.py
new file mode 100644
index 000000000000..3d7404bf6e0b
--- /dev/null
+++ b/tools/perf/tests/shell/lib/perf_json_output_lint.py
@@ -0,0 +1,90 @@
+#!/usr/bin/python
+# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+# Basic sanity check of perf JSON output as specified in the man page.
+
+from __future__ import print_function
+import argparse
+import sys
+import json
+
+ap = argparse.ArgumentParser()
+ap.add_argument('--no-args', action='store_true')
+ap.add_argument('--interval', action='store_true')
+ap.add_argument('--system-wide-no-aggr', action='store_true')
+ap.add_argument('--system-wide', action='store_true')
+ap.add_argument('--event', action='store_true')
+ap.add_argument('--per-core', action='store_true')
+ap.add_argument('--per-thread', action='store_true')
+ap.add_argument('--per-die', action='store_true')
+ap.add_argument('--per-node', action='store_true')
+ap.add_argument('--per-socket', action='store_true')
+args = ap.parse_args()
+
+Lines = sys.stdin.readlines()
+
+def isfloat(num):
+  try:
+    float(num)
+    return True
+  except ValueError:
+    return False
+
+
+def isint(num):
+  try:
+    int(num)
+    return True
+  except ValueError:
+    return False
+
+
+def check_json_output(expected_items):
+  if expected_items != -1:
+    for line in Lines:
+      if 'failed' not in line:
+        count = 0
+        count = line.count(',')
+        if count != expected_items:
+          raise RuntimeError('wrong number of fields. counted {0}'
+                             ' expected {1} in {2}\n'.format(count, exp, line))
+  checks = {
+      'aggregate-number': lambda x: isfloat(x),
+      'core': lambda x: True,
+      'counter-value': lambda x: isfloat(x),
+      'cgroup': lambda x: True,
+      'cpu': lambda x: isint(x),
+      'die': lambda x: True,
+      'event': lambda x: True,
+      'event-runtime': lambda x: isfloat(x),
+      'interval': lambda x: isfloat(x),
+      'metric-unit': lambda x: True,
+      'metric-value': lambda x: isfloat(x),
+      'node': lambda x: True,
+      'pcnt-running': lambda x: isfloat(x),
+      'socket': lambda x: True,
+      'thread': lambda x: True,
+      'unit': lambda x: True,
+  }
+  input = '[\n' + ','.join(Lines) + '\n]'
+  for item in json.loads(input):
+    for key, value in item.items():
+      if not key in checks:
+        raise RuntimeError(f'Unexpected key: key={key} value={value}')
+      if not checks[key](value):
+        raise RuntimeError(f'Check failed for: key={key} value={value}')
+
+
+try:
+  if args.no_args or args.system_wide or args.event:
+    expected_items = 6
+  elif args.interval or args.per_thread or args.system_wide_no_aggr:
+    expected_items = 7
+  elif args.per_core or args.per_socket or args.per_node or args.per_die:
+    expected_items = 8
+  else:
+    # If no option is specified, don't check the number of items.
+    expected_items = -1
+  check_json_output(expected_items)
+except:
+  print('Test failed for input:\n' + '\n'.join(Lines))
+  raise
diff --git a/tools/perf/tests/shell/stat+json_output.sh b/tools/perf/tests/shell/stat+json_output.sh
new file mode 100755
index 000000000000..7b3745f3eeb8
--- /dev/null
+++ b/tools/perf/tests/shell/stat+json_output.sh
@@ -0,0 +1,141 @@
+#!/bin/bash
+# perf stat JSON output linter
+# SPDX-License-Identifier: GPL-2.0
+# Checks various perf stat JSON output commands for the
+# correct number of fields.
+
+set -e
+
+pythonchecker=$(dirname $0)/lib/perf_json_output_lint.py
+if [ "x$PYTHON" == "x" ]
+then
+	if which python3 > /dev/null
+	then
+		PYTHON=python3
+	elif which python > /dev/null
+	then
+		PYTHON=python
+	else
+		echo Skipping test, python not detected please set environment variable PYTHON.
+		exit 2
+	fi
+fi
+
+# Return true if perf_event_paranoid is > $1 and not running as root.
+function ParanoidAndNotRoot()
+{
+	 [ $(id -u) != 0 ] && [ $(cat /proc/sys/kernel/perf_event_paranoid) -gt $1 ]
+}
+
+check_no_args()
+{
+	echo -n "Checking json output: no args "
+	perf stat -j true 2>&1 | $PYTHON $pythonchecker --no-args
+	echo "[Success]"
+}
+
+check_system_wide()
+{
+	echo -n "Checking json output: system wide "
+	if ParanoidAndNotRoot 0
+	then
+		echo "[Skip] parnoia and not root"
+		return
+	fi
+	perf stat -j -a true 2>&1 | $PYTHON $pythonchecker --system-wide
+	echo "[Success]"
+}
+
+check_system_wide_no_aggr()
+{
+	echo -n "Checking json output: system wide no aggregation "
+	perf stat -j -A -a --no-merge true 2>&1 | $PYTHON $pythonchecker --system-wide-no-aggr
+	echo "[Success]"
+}
+
+check_interval()
+{
+	echo -n "Checking json output: interval "
+	perf stat -j -I 1000 true 2>&1 | $PYTHON $pythonchecker --interval
+	echo "[Success]"
+}
+
+
+check_event()
+{
+	echo -n "Checking json output: event "
+	perf stat -j -e cpu-clock true 2>&1 | $PYTHON $pythonchecker --event
+	echo "[Success]"
+}
+
+check_per_core()
+{
+	echo -n "Checking json output: per core "
+	if ParanoidAndNotRoot 0
+	then
+		echo "[Skip] parnoia and not root"
+		return
+	fi
+	perf stat -j --per-core -a true 2>&1 | $PYTHON $pythonchecker --per-core
+	echo "[Success]"
+}
+
+check_per_thread()
+{
+	echo -n "Checking json output: per thread "
+	if ParanoidAndNotRoot 0
+	then
+		echo "[Skip] parnoia and not root"
+		return
+	fi
+	perf stat -j --per-thread -a true 2>&1 | $PYTHON $pythonchecker --per-thread
+	echo "[Success]"
+}
+
+check_per_die()
+{
+	echo -n "Checking json output: per die "
+	if ParanoidAndNotRoot 0
+	then
+		echo "[Skip] parnoia and not root"
+		return
+	fi
+	perf stat -j --per-die -a true 2>&1 | $PYTHON $pythonchecker --per-die
+	echo "[Success]"
+}
+
+check_per_node()
+{
+	echo -n "Checking json output: per node "
+	if ParanoidAndNotRoot 0
+	then
+		echo "[Skip] parnoia and not root"
+		return
+	fi
+	perf stat -j --per-node -a true 2>&1 | $PYTHON $pythonchecker --per-node
+	echo "[Success]"
+}
+
+check_per_socket()
+{
+	echo -n "Checking json output: per socket "
+	if ParanoidAndNotRoot 0
+	then
+		echo "[Skip] parnoia and not root"
+		return
+	fi
+	perf stat -j --per-socket -a true 2>&1 | $PYTHON $pythonchecker --per-socket
+	echo "[Success]"
+}
+
+check_no_args
+check_system_wide
+check_system_wide_no_aggr
+check_interval
+check_event
+check_per_core
+check_per_thread
+check_per_die
+check_per_node
+check_per_socket
+exit 0
-- 
2.36.0.550.gb090851708-goog