[PATCH] perf stat: improve readability of shadow stats

Changbin Du
2021-03-01T21:57:50Z

This does follow two changes:
1) Select appropriate unit between K/M/G.
2) Use 'cpu-sec' instead of 'sec' to state this is not the wall-time.

$ sudo ./perf stat -a -- sleep 1

Before: Unit 'M' is selected even the number is very small.
Performance counter stats for 'system wide':

4,003.06 msec cpu-clock # 3.998 CPUs utilized
16,179 context-switches # 0.004 M/sec
161 cpu-migrations # 0.040 K/sec
4,699 page-faults # 0.001 M/sec
6,135,801,925 cycles # 1.533 GHz (83.21%)
5,783,308,491 stalled-cycles-frontend # 94.26% frontend cycles idle (83.21%)
4,543,694,050 stalled-cycles-backend # 74.05% backend cycles idle (66.49%)
4,720,130,587 instructions # 0.77 insn per cycle
# 1.23 stalled cycles per insn (83.28%)
753,848,078 branches # 188.318 M/sec (83.61%)
37,457,747 branch-misses # 4.97% of all branches (83.48%)

1.001283725 seconds time elapsed

After:
$ sudo ./perf stat -a -- sleep 2

Performance counter stats for 'system wide':

8,003.20 msec cpu-clock # 3.998 CPUs utilized
9,768 context-switches # 1.221 K/cpu-sec
164 cpu-migrations # 20.492 /cpu-sec
74,146 page-faults # 9.265 K/cpu-sec
19,008,796,806 cycles # 2.375 GHz (83.21%)
14,789,443,853 stalled-cycles-frontend # 77.80% frontend cycles idle (83.29%)
11,867,812,064 stalled-cycles-backend # 62.43% backend cycles idle (66.80%)
9,898,252,603 instructions # 0.52 insn per cycle
# 1.49 stalled cycles per insn (83.41%)
2,063,251,998 branches # 257.803 M/cpu-sec (83.41%)
86,941,704 branch-misses # 4.21% of all branches (83.30%)

2.001743706 seconds time elapsed

Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
tools/perf/util/stat-shadow.c | 13 +++++--------
tools/perf/util/units.c | 22 ++++++++++++++++++++++
tools/perf/util/units.h | 1 +
3 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index 6ccf21a72f06..786b5ef512d8 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -9,6 +9,7 @@
#include "expr.h"
#include "metricgroup.h"
#include "cgroup.h"
+#include "units.h"
#include <linux/zalloc.h>

/*
@@ -1270,18 +1271,14 @@ void perf_stat__print_shadow_stats(struct perf_stat_config *config,
generic_metric(config, evsel->metric_expr, evsel->metric_events, NULL,
evsel->name, evsel->metric_name, NULL, 1, cpu, out, st);
} else if (runtime_stat_n(st, STAT_NSECS, cpu, &rsd) != 0) {
- char unit = 'M';
+ char unit = ' ';
char unit_buf[10];

total = runtime_stat_avg(st, STAT_NSECS, cpu, &rsd);
-
if (total)
- ratio = 1000.0 * avg / total;
- if (ratio < 0.001) {
- ratio *= 1000;
- unit = 'K';
- }
- snprintf(unit_buf, sizeof(unit_buf), "%c/sec", unit);
+ ratio = convert_unit_double(1000000000.0 * avg / total, &unit);
+
+ snprintf(unit_buf, sizeof(unit_buf), "%c/cpu-sec", unit);
print_metric(config, ctxp, NULL, "%8.3f", unit_buf, ratio);
} else if (perf_stat_evsel__is(evsel, SMI_NUM)) {
print_smi_cost(config, cpu, out, st, &rsd);
diff --git a/tools/perf/util/units.c b/tools/perf/util/units.c
index a46762aec4c9..ac13b5ecde31 100644
--- a/tools/perf/util/units.c
+++ b/tools/perf/util/units.c
@@ -55,6 +55,28 @@ unsigned long convert_unit(unsigned long value, char *unit)
return value;
}

+double convert_unit_double(double value, char *unit)
+{
+ *unit = ' ';
+
+ if (value > 1000.0) {
+ value /= 1000.0;
+ *unit = 'K';
+ }
+
+ if (value > 1000.0) {
+ value /= 1000.0;
+ *unit = 'M';
+ }
+
+ if (value > 1000.0) {
+ value /= 1000.0;
+ *unit = 'G';
+ }
+
+ return value;
+}
+
int unit_number__scnprintf(char *buf, size_t size, u64 n)
{
char unit[4] = "BKMG";
diff --git a/tools/perf/util/units.h b/tools/perf/util/units.h
index 99263b6a23f7..b3ace67ac16f 100644
--- a/tools/perf/util/units.h
+++ b/tools/perf/util/units.h
@@ -13,6 +13,7 @@ struct parse_tag {
unsigned long parse_tag_value(const char *str, struct parse_tag *tags);

unsigned long convert_unit(unsigned long value, char *unit);
+double convert_unit_double(double value, char *unit);
int unit_number__scnprintf(char *buf, size_t size, u64 n);

#endif /* PERF_UNIT_H */
--
2.25.1