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perf, tools: Refactor and support interval and CSV metrics

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  perf, tools: Refactor and support interval and CSV metrics Andi Kleen <andi@firstfloor.org> - 2016-02-27 01:30 +0100
    [PATCH 6/6] perf, tools, stat: Add --metric-only support for -A Andi Kleen <andi@firstfloor.org> - 2016-02-27 01:30 +0100
    [PATCH 5/6] perf, tools, stat: Implement --metric-only mode Andi Kleen <andi@firstfloor.org> - 2016-02-27 01:30 +0100
    [PATCH 4/6] perf, tools, stat: Document CSV format in manpage Andi Kleen <andi@firstfloor.org> - 2016-02-27 01:30 +0100

#1344866 — perf, tools: Refactor and support interval and CSV metrics

[v5: Fix mainly bisect problems. No regressions introduced by one
patch and fixed again later. Some minor fixes in addition]
[v6: Fix running/noise printing patch.]
[v7: Reorder and merge two patches to avoid a bisect hole where unsupported was
printed as 0]
[v8: Minor fixes for review feedback. See changelog in patches.]
[v9: Fix newline bug. Add support for -A for --metric-only]
[v10: Remove extra "noise" printing (Jiri)
      Fix fields in documentation (Jiri)]
[v11: Fix manpage again. Avoid extra metric output in CSV mode.]
[v12: Move CSV metrics fields to after running/enabled/variance.
      Minor fixes.]
[v13: Address review comments. Now probe for stalled events 
      in advance to avoid empty columns or lines. Fix -A shadowing.
      Various minor changes. Drop merged patches.]

Currently perf stat does not support printing computed metrics for interval (-I xxx)
or CSV (-x,) mode. For example IPC or TSX metrics over time are quite useful to know.

This patch implements them. The main obstacle was that the
metrics printing was all open coded all over the metrics computation code.
The second patch refactors the metrics printing to work through call backs that
can be more easily changed. This also cleans up the metrics printing significantly.
The indentation is now handled through printf, no more need to manually count spaces.

Then based on that it implements metrics printing for CSV and interval mode,
and finally a --metric-only mode.

Example output:

% perf stat  -I1000 -a sleep 1
#          time              counts unit events                    metric                              multiplex
     1.001301370       12020.049593      task-clock (msec)                                             (100.00%)
     1.001301370              3,952      context-switches          #    0.329 K/sec                    (100.00%)
     1.001301370                 69      cpu-migrations            #    0.006 K/sec                    (100.00%)
     1.001301370                 76      page-faults               #    0.006 K/sec                  
     1.001301370        386,582,789      cycles                    #    0.032 GHz                      (100.00%)
     1.001301370        716,441,544      stalled-cycles-frontend   #  185.33% frontend cycles idle     (100.00%)
     1.001301370    <not supported>      stalled-cycles-backend   
     1.001301370        101,751,678      instructions              #    0.26  insn per cycle         
     1.001301370                                                   #    7.04  stalled cycles per insn  (100.00%)
     1.001301370         20,914,692      branches                  #    1.740 M/sec                    (100.00%)
     1.001301370          1,943,630      branch-misses             #    9.29% of all branches        

CSV mode:

% perf stat  -x, -I1000 -a sleep 1
     1.000982778,12006.549977,,task-clock,12006547787,100.00,,,,
     1.000982778,12822,,context-switches,12007100604,100.00,0.001,M/sec
     1.000982778,175,,cpu-migrations,12007180306,100.00,0.015,K/sec
     1.000982778,3404,,page-faults,12007185482,100.00,0.284,K/sec
     1.000982778,1930307489,,cycles,12007018233,100.00,0.161,GHz
     1.000982778,6971803638,,stalled-cycles-frontend,12006902870,100.00,361.18,frontend cycles idle
     1.000982778,464493941,,instructions,12006873327,100.00,0.24,insn per cycle
     1.000982778,,,,,,15.01,stalled cycles per insn
     1.000982778,86548409,,branches,12006758420,100.00,7.208,M/sec
     1.000982778,4933638,,branch-misses,12006648104,100.00,5.70,of all branches

Now includes metrics

Metric only mode:

Concicse information if you only care about computed metrics, not raw values

% perf stat --metric-only  -a -I 1000
         1.001452803 frontend cycles idle insn per cycle       stalled cycles per insn branch-misses of all branches
         1.001452803  158.91%               0.66                2.39                    2.92%
         2.002192321  180.63%               0.76                2.08                    2.96%
         3.003088282  150.59%               0.62                2.57                    2.84%
         4.004369835  196.20%               0.98                1.62                    3.79%
         5.005227314  231.98%               0.84                1.90                    4.71%


Metric only mode in CSV (flat format, easy to plot and analyze in statistical tools like JMP, R, pandas, gnuplot):

% perf stat -x, --metric-only  -a -I 1000
     1.001381652,frontend cycles idle,insn per cycle,stalled cycles per insn,branch-misses of all branches,
     1.001381652,173.32,0.83,2.09,1.73,
     2.002073343,199.47,1.07,1.60,2.14,
     3.002875524,109.52,0.22,7.83,1.63,
     4.003970059,132.10,0.17,10.85,1.51,
     5.004818754,181.60,0.22,8.87,2.22,


Available in
git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc-2.6 perf/stat-metrics-17

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#1344867 — [PATCH 6/6] perf, tools, stat: Add --metric-only support for -A

From: Andi Kleen <ak@linux.intel.com>

Add metric only support for -A too. This requires a new print
function that prints the metrics in the right order.

v2: Fix manpage
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/Documentation/perf-stat.txt |  2 +-
 tools/perf/builtin-stat.c              | 48 ++++++++++++++++++++++++++++------
 2 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 3929ab0..44095cd 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -141,7 +141,7 @@ The overhead percentage could be high in some cases, for instance with small, su
 
 --metric-only::
 Only print computed metrics. Print them in a single line.
-Don't show any raw values. Not supported with -A or --per-thread.
+Don't show any raw values. Not supported with --per-thread.
 
 --per-socket::
 Aggregate counts per processor socket for system-wide mode measurements.  This
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 30bb0ac..78a4205 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -1243,10 +1243,43 @@ static void print_counter(struct perf_evsel *counter, char *prefix)
 	}
 }
 
+static void print_no_aggr_metric(char *prefix)
+{
+	int cpu;
+	int nrcpus = 0;
+	struct perf_evsel *counter;
+	u64 ena, run, val;
+	double uval;
+
+	evlist__for_each(evsel_list, counter) {
+		nrcpus = perf_evsel__nr_cpus(counter);
+		break;
+	}
+	for (cpu = 0; cpu < nrcpus; cpu++) {
+		bool first = true;
+
+		if (prefix)
+			fputs(prefix, stat_config.output);
+		evlist__for_each(evsel_list, counter) {
+			if (first) {
+				aggr_printout(counter, cpu, 0);
+				first = false;
+			}
+			val = perf_counts(counter->counts, cpu, 0)->val;
+			ena = perf_counts(counter->counts, cpu, 0)->ena;
+			run = perf_counts(counter->counts, cpu, 0)->run;
+
+			uval = val * counter->scale;
+			printout(cpu, 0, counter, uval, prefix, run, ena, 1.0);
+		}
+		fputc('\n', stat_config.output);
+	}
+}
+
 static int aggr_header_lens[] = {
 	[AGGR_CORE] = 18,
 	[AGGR_SOCKET] = 12,
-	[AGGR_NONE] = 15,
+	[AGGR_NONE] = 6,
 	[AGGR_THREAD] = 24,
 	[AGGR_GLOBAL] = 0,
 };
@@ -1401,8 +1434,12 @@ static void print_counters(struct timespec *ts, int argc, const char **argv)
 			fputc('\n', stat_config.output);
 		break;
 	case AGGR_NONE:
-		evlist__for_each(evsel_list, counter)
-			print_counter(counter, prefix);
+		if (metric_only)
+			print_no_aggr_metric(prefix);
+		else {
+			evlist__for_each(evsel_list, counter)
+				print_counter(counter, prefix);
+		}
 		break;
 	case AGGR_UNSET:
 	default:
@@ -2170,11 +2207,6 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
 		goto out;
 	}
 
-	if (metric_only && stat_config.aggr_mode == AGGR_NONE) {
-		fprintf(stderr, "--metric-only is not supported with -A\n");
-		goto out;
-	}
-
 	if (metric_only && run_count > 1) {
 		fprintf(stderr, "--metric-only is not supported with -r\n");
 		goto out;
-- 
2.5.0

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#1344868 — [PATCH 5/6] perf, tools, stat: Implement --metric-only mode

From: Andi Kleen <ak@linux.intel.com>

Add a new mode to only print metrics. Sometimes we don't care about
the raw values, just want the computed metrics. This allows more
compact printing, so with -I each sample is only a single line.
This also allows easier plotting and processing with other tools.

The main target is with using --topdown, but it also works with
-T and standard perf stat. A few metrics are not supported.

To avoiding having to hardcode all the metrics in the code it uses
a two pass approach: first compute dummy metrics and only
print the headers in the print_metric callback. Then use the callback
to print the actual values.

There are some additional changes
in the stat printout code to handle all metrics being on a single line.

One issue is that the column code doesn't know in advance what events
are not supported by the CPU, and it would be hard to find out
as this could change based on dynamic conditions. That causes
empty columns in some cases.

The output can be fairly wide, often you may need more than 80 columns.

Example:

% perf stat -a -I 1000 --metric-only
     1.001452803 frontend cycles idle insn per cycle       stalled cycles per insn branch-misses of all branches
     1.001452803  158.91%               0.66                2.39                    2.92%
     2.002192321  180.63%               0.76                2.08                    2.96%
     3.003088282  150.59%               0.62                2.57                    2.84%
     4.004369835  196.20%               0.98                1.62                    3.79%
     5.005227314  231.98%               0.84                1.90                    4.71%

v2: Lots of updates.
v3: Use slightly narrower columns
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/Documentation/perf-stat.txt |   4 +
 tools/perf/builtin-stat.c              | 207 +++++++++++++++++++++++++++++++--
 2 files changed, 201 insertions(+), 10 deletions(-)

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 3ae7907..3929ab0 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -139,6 +139,10 @@ Print count deltas every N milliseconds (minimum: 10ms)
 The overhead percentage could be high in some cases, for instance with small, sub 100ms intervals.  Use with caution.
 	example: 'perf stat -I 1000 -e cycles -a sleep 5'
 
+--metric-only::
+Only print computed metrics. Print them in a single line.
+Don't show any raw values. Not supported with -A or --per-thread.
+
 --per-socket::
 Aggregate counts per processor socket for system-wide mode measurements.  This
 is a useful mode to detect imbalance between sockets.  To enable this mode,
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index c79e571..30bb0ac 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -122,6 +122,7 @@ static bool			sync_run			= false;
 static unsigned int		initial_delay			= 0;
 static unsigned int		unit_width			= 4; /* strlen("unit") */
 static bool			forever				= false;
+static bool			metric_only			= false;
 static struct timespec		ref_time;
 static struct cpu_map		*aggr_map;
 static aggr_get_id_t		aggr_get_id;
@@ -827,6 +828,99 @@ static void print_metric_csv(void *ctx,
 	fprintf(out, "%s%s%s%s", csv_sep, vals, csv_sep, unit);
 }
 
+#define METRIC_ONLY_LEN 20
+
+/* Filter out some columns that don't work well in metrics only mode */
+
+static bool valid_only_metric(const char *unit)
+{
+	if (!unit)
+		return false;
+	if (strstr(unit, "/sec") ||
+	    strstr(unit, "hz") ||
+	    strstr(unit, "Hz") ||
+	    strstr(unit, "CPUs utilized"))
+		return false;
+	return true;
+}
+
+static const char *fixunit(char *buf, struct perf_evsel *evsel,
+			   const char *unit)
+{
+	if (!strncmp(unit, "of all", 6)) {
+		snprintf(buf, 1024, "%s %s", perf_evsel__name(evsel),
+			 unit);
+		return buf;
+	}
+	return unit;
+}
+
+static void print_metric_only(void *ctx, const char *color, const char *fmt,
+			      const char *unit, double val)
+{
+	struct outstate *os = ctx;
+	FILE *out = os->fh;
+	int n;
+	char buf[1024];
+	unsigned mlen = METRIC_ONLY_LEN;
+
+	if (!valid_only_metric(unit))
+		return;
+	unit = fixunit(buf, os->evsel, unit);
+	if (color)
+		n = color_fprintf(out, color, fmt, val);
+	else
+		n = fprintf(out, fmt, val);
+	if (n > METRIC_ONLY_LEN)
+		n = METRIC_ONLY_LEN;
+	if (mlen < strlen(unit))
+		mlen = strlen(unit) + 1;
+	fprintf(out, "%*s", mlen - n, "");
+}
+
+static void print_metric_only_csv(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);
+	vals = buf;
+	while (isspace(*vals))
+		vals++;
+	ends = vals;
+	while (isdigit(*ends) || *ends == '.')
+		ends++;
+	*ends = 0;
+	fprintf(out, "%s%s", vals, csv_sep);
+}
+
+static void new_line_metric(void *ctx __maybe_unused)
+{
+}
+
+static void print_metric_header(void *ctx, const char *color __maybe_unused,
+				const char *fmt __maybe_unused,
+				const char *unit, double val __maybe_unused)
+{
+	struct outstate *os = ctx;
+	char tbuf[1024];
+
+	if (!valid_only_metric(unit))
+		return;
+	unit = fixunit(tbuf, os->evsel, unit);
+	if (csv_output)
+		fprintf(os->fh, "%s%s", unit, csv_sep);
+	else
+		fprintf(os->fh, "%-*s ", METRIC_ONLY_LEN, unit);
+}
+
 static void nsec_printout(int id, int nr, struct perf_evsel *evsel, double avg)
 {
 	FILE *output = stat_config.output;
@@ -918,9 +1012,16 @@ static void printout(int id, int nr, struct perf_evsel *counter, double uval,
 	print_metric_t pm = print_metric_std;
 	void (*nl)(void *);
 
-	nl = new_line_std;
+	if (metric_only) {
+		nl = new_line_metric;
+		if (csv_output)
+			pm = print_metric_only_csv;
+		else
+			pm = print_metric_only;
+	} else
+		nl = new_line_std;
 
-	if (csv_output) {
+	if (csv_output && !metric_only) {
 		static int aggr_fields[] = {
 			[AGGR_GLOBAL] = 0,
 			[AGGR_THREAD] = 1,
@@ -937,6 +1038,10 @@ static void printout(int id, int nr, struct perf_evsel *counter, double uval,
 			os.nfields++;
 	}
 	if (run == 0 || ena == 0 || counter->counts->scaled == -1) {
+		if (metric_only) {
+			pm(&os, NULL, "", "", 0);
+			return;
+		}
 		aggr_printout(counter, id, nr);
 
 		fprintf(stat_config.output, "%*s%s",
@@ -965,7 +1070,9 @@ static void printout(int id, int nr, struct perf_evsel *counter, double uval,
 		return;
 	}
 
-	if (nsec_counter(counter))
+	if (metric_only)
+		/* nothing */;
+	else if (nsec_counter(counter))
 		nsec_printout(id, nr, counter, uval);
 	else
 		abs_printout(id, nr, counter, uval);
@@ -974,7 +1081,7 @@ static void printout(int id, int nr, struct perf_evsel *counter, double uval,
 	out.new_line = nl;
 	out.ctx = &os;
 
-	if (csv_output) {
+	if (csv_output && !metric_only) {
 		print_noise(counter, noise);
 		print_running(run, ena);
 	}
@@ -982,7 +1089,7 @@ static void printout(int id, int nr, struct perf_evsel *counter, double uval,
 	perf_stat__print_shadow_stats(counter, uval,
 				first_shadow_cpu(counter, id),
 				&out);
-	if (!csv_output) {
+	if (!csv_output && !metric_only) {
 		print_noise(counter, noise);
 		print_running(run, ena);
 	}
@@ -1018,6 +1125,7 @@ static void print_aggr(char *prefix)
 	int cpu, s, s2, id, nr;
 	double uval;
 	u64 ena, run, val;
+	bool first;
 
 	if (!(aggr_map || aggr_get_id))
 		return;
@@ -1025,7 +1133,11 @@ static void print_aggr(char *prefix)
 	aggr_update_shadow();
 
 	for (s = 0; s < aggr_map->nr; s++) {
+		if (prefix && metric_only)
+			fprintf(output, "%s", prefix);
+
 		id = aggr_map->map[s];
+		first = true;
 		evlist__for_each(evsel_list, counter) {
 			val = ena = run = 0;
 			nr = 0;
@@ -1038,13 +1150,20 @@ static void print_aggr(char *prefix)
 				run += perf_counts(counter->counts, cpu, 0)->run;
 				nr++;
 			}
-			if (prefix)
+			if (first && metric_only) {
+				first = false;
+				aggr_printout(counter, id, nr);
+			}
+			if (prefix && !metric_only)
 				fprintf(output, "%s", prefix);
 
 			uval = val * counter->scale;
 			printout(id, nr, counter, uval, prefix, run, ena, 1.0);
-			fputc('\n', output);
+			if (!metric_only)
+				fputc('\n', output);
 		}
+		if (metric_only)
+			fputc('\n', output);
 	}
 }
 
@@ -1089,12 +1208,13 @@ static void print_counter_aggr(struct perf_evsel *counter, char *prefix)
 	avg_enabled = avg_stats(&ps->res_stats[1]);
 	avg_running = avg_stats(&ps->res_stats[2]);
 
-	if (prefix)
+	if (prefix && !metric_only)
 		fprintf(output, "%s", prefix);
 
 	uval = avg * counter->scale;
 	printout(-1, 0, counter, uval, prefix, avg_running, avg_enabled, avg);
-	fprintf(output, "\n");
+	if (!metric_only)
+		fprintf(output, "\n");
 }
 
 /*
@@ -1123,6 +1243,43 @@ static void print_counter(struct perf_evsel *counter, char *prefix)
 	}
 }
 
+static int aggr_header_lens[] = {
+	[AGGR_CORE] = 18,
+	[AGGR_SOCKET] = 12,
+	[AGGR_NONE] = 15,
+	[AGGR_THREAD] = 24,
+	[AGGR_GLOBAL] = 0,
+};
+
+static void print_metric_headers(char *prefix)
+{
+	struct perf_stat_output_ctx out;
+	struct perf_evsel *counter;
+	struct outstate os = {
+		.fh = stat_config.output
+	};
+
+	if (prefix)
+		fprintf(stat_config.output, "%s", prefix);
+
+	if (!csv_output)
+		fprintf(stat_config.output, "%*s",
+			aggr_header_lens[stat_config.aggr_mode], "");
+
+	/* Print metrics headers only */
+	evlist__for_each(evsel_list, counter) {
+		os.evsel = counter;
+		out.ctx = &os;
+		out.print_metric = print_metric_header;
+		out.new_line = new_line_metric;
+		os.evsel = counter;
+		perf_stat__print_shadow_stats(counter, 0,
+					      0,
+					      &out);
+	}
+	fputc('\n', stat_config.output);
+}
+
 static void print_interval(char *prefix, struct timespec *ts)
 {
 	FILE *output = stat_config.output;
@@ -1130,7 +1287,7 @@ static void print_interval(char *prefix, struct timespec *ts)
 
 	sprintf(prefix, "%6lu.%09lu%s", ts->tv_sec, ts->tv_nsec, csv_sep);
 
-	if (num_print_interval == 0 && !csv_output) {
+	if (num_print_interval == 0 && !csv_output && !metric_only) {
 		switch (stat_config.aggr_mode) {
 		case AGGR_SOCKET:
 			fprintf(output, "#           time socket cpus             counts %*s events\n", unit_width, "unit");
@@ -1217,6 +1374,17 @@ static void print_counters(struct timespec *ts, int argc, const char **argv)
 	else
 		print_header(argc, argv);
 
+	if (metric_only) {
+		static int num_print_iv;
+
+		if (num_print_iv == 0)
+			print_metric_headers(prefix);
+		if (num_print_iv++ == 25)
+			num_print_iv = 0;
+		if (stat_config.aggr_mode == AGGR_GLOBAL && prefix)
+			fprintf(stat_config.output, "%s", prefix);
+	}
+
 	switch (stat_config.aggr_mode) {
 	case AGGR_CORE:
 	case AGGR_SOCKET:
@@ -1229,6 +1397,8 @@ static void print_counters(struct timespec *ts, int argc, const char **argv)
 	case AGGR_GLOBAL:
 		evlist__for_each(evsel_list, counter)
 			print_counter_aggr(counter, prefix);
+		if (metric_only)
+			fputc('\n', stat_config.output);
 		break;
 	case AGGR_NONE:
 		evlist__for_each(evsel_list, counter)
@@ -1353,6 +1523,8 @@ static const struct option stat_options[] = {
 		     "aggregate counts per thread", AGGR_THREAD),
 	OPT_UINTEGER('D', "delay", &initial_delay,
 		     "ms to wait before starting measurement after program start"),
+	OPT_BOOLEAN(0, "metric-only", &metric_only,
+			"Only print computed metrics. No raw values"),
 	OPT_END()
 };
 
@@ -1993,6 +2165,21 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
 		goto out;
 	}
 
+	if (metric_only && stat_config.aggr_mode == AGGR_THREAD) {
+		fprintf(stderr, "--metric-only is not supported with --per-thread\n");
+		goto out;
+	}
+
+	if (metric_only && stat_config.aggr_mode == AGGR_NONE) {
+		fprintf(stderr, "--metric-only is not supported with -A\n");
+		goto out;
+	}
+
+	if (metric_only && run_count > 1) {
+		fprintf(stderr, "--metric-only is not supported with -r\n");
+		goto out;
+	}
+
 	if (output_fd < 0) {
 		fprintf(stderr, "argument to --log-fd must be a > 0\n");
 		parse_options_usage(stat_usage, stat_options, "log-fd", 0);
-- 
2.5.0

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#1344869 — [PATCH 4/6] perf, tools, stat: Document CSV format in manpage

From: Andi Kleen <ak@linux.intel.com>

With all the recently added fields in the perf stat CSV output
we should finally document them in the man page. Do this here.

v2: Fix fields in documentation (Jiri)
v3: fix order of fields again (Jiri)
v4: Change order again.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/Documentation/perf-stat.txt | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 52ef7a9..3ae7907 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -211,6 +211,27 @@ $ perf stat -- make -j
 
  Wall-clock time elapsed:   719.554352 msecs
 
+CSV FORMAT
+----------
+
+With -x, perf stat is able to output a not-quite-CSV format output
+Commas in the output are not put into "". To make it easy to parse
+it is recommended to use a different character like -x \;
+
+The fields are in this order:
+
+	- optional usec time stamp in fractions of second (with -I xxx)
+	- counter value
+	- unit of the counter value or empty
+	- event name
+	- run time of counter
+	- percentage of measurement time the counter was running
+	- optional variance if multiple values are collected with -r
+	- optional metric value
+	- optional unit of metric
+
+Additional metrics may be printed with all earlier fields being empty.
+
 SEE ALSO
 --------
 linkperf:perf-top[1], linkperf:perf-list[1]
-- 
2.5.0

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