Re: [RESEND PATCH v2] perf stat: improve readability of shadow stats

[Namhyung Kim <namhyung@kernel.org>]

Hello,

On Mon, Mar 15, 2021 at 11:31 PM Changbin Du <changbin.du@gmail.com> wrote:
>
> This adds function convert_unit_double() and selects appropriate
> unit for shadow stats between K/M/G.
>
> $ 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':
>
>           8,005.52 msec cpu-clock                 #    3.999 CPUs utilized
>             10,715      context-switches          #    1.338 K/sec
>                785      cpu-migrations            #   98.057 /sec
>                102      page-faults               #   12.741 /sec
>      1,948,202,279      cycles                    #    0.243 GHz
>      2,816,470,932      stalled-cycles-frontend   #  144.57% frontend cycles idle
>      2,661,172,207      stalled-cycles-backend    #  136.60% backend cycles idle
>        464,172,105      instructions              #    0.24  insn per cycle
>                                                   #    6.07  stalled cycles per insn
>         91,567,662      branches                  #   11.438 M/sec
>          7,756,054      branch-misses             #    8.47% of all branches
>
>        2.002040043 seconds time elapsed
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung

>
> v2:
>   o do not change 'sec' to 'cpu-sec'.
>   o use convert_unit_double to implement convert_unit.
> ---
>  tools/perf/util/stat-shadow.c | 16 +++++++---------
>  tools/perf/util/units.c       | 21 ++++++++++++++-------
>  tools/perf/util/units.h       |  1 +
>  3 files changed, 22 insertions(+), 16 deletions(-)
>
> diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
> index 6ccf21a72f06..3f800e71126f 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 +1271,15 @@ 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_buf[10];
> +               char unit = ' ';
> +               char unit_buf[10] = "/sec";
>
>                 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);
> +
> +               if (unit != ' ')
> +                       snprintf(unit_buf, sizeof(unit_buf), "%c/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..32c39cfe209b 100644
> --- a/tools/perf/util/units.c
> +++ b/tools/perf/util/units.c
> @@ -33,28 +33,35 @@ unsigned long parse_tag_value(const char *str, struct parse_tag *tags)
>         return (unsigned long) -1;
>  }
>
> -unsigned long convert_unit(unsigned long value, char *unit)
> +double convert_unit_double(double value, char *unit)
>  {
>         *unit = ' ';
>
> -       if (value > 1000) {
> -               value /= 1000;
> +       if (value > 1000.0) {
> +               value /= 1000.0;
>                 *unit = 'K';
>         }
>
> -       if (value > 1000) {
> -               value /= 1000;
> +       if (value > 1000.0) {
> +               value /= 1000.0;
>                 *unit = 'M';
>         }
>
> -       if (value > 1000) {
> -               value /= 1000;
> +       if (value > 1000.0) {
> +               value /= 1000.0;
>                 *unit = 'G';
>         }
>
>         return value;
>  }
>
> +unsigned long convert_unit(unsigned long value, char *unit)
> +{
> +       double v = convert_unit_double((double)value, unit);
> +
> +       return (unsigned long)v;
> +}
> +
>  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..ea43e74e3240 100644
> --- a/tools/perf/util/units.h
> +++ b/tools/perf/util/units.h
> @@ -12,6 +12,7 @@ struct parse_tag {
>
>  unsigned long parse_tag_value(const char *str, struct parse_tag *tags);
>
> +double convert_unit_double(double value, char *unit);
>  unsigned long convert_unit(unsigned long value, char *unit);
>  int unit_number__scnprintf(char *buf, size_t size, u64 n);
>
> --
> 2.25.1
>