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Date: Tue, 2 Mar 2021 12:23:25 +0530
From: kajoljain <kjain@...ux.ibm.com>
To: Changbin Du <changbin.du@...il.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf stat: improve readability of shadow stats
On 3/1/21 10:54 PM, Changbin Du wrote:
> 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@...il.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;
> }
>
Hi Changbin,
Since we are using added function `convert_unit_double` just in stat-shadow.c,
I think there is no need to add it in units.h, we can directly create static func inside `stat-shadow.c`itself.
Thanks,
Kajol Jain
> +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 */
>
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