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

Changbin Du
2021-03-04T16:23:48Z

On Mon, Mar 01, 2021 at 08:19:20PM +0100, Jiri Olsa wrote:
> On Tue, Mar 02, 2021 at 01:24:02AM +0800, 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
>
> should you remove also the leading '/' in ' /cpu-sec' ?
>
>
> SNIP
>
> > @@ -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);
>
> hum this will change -x output that people parse, so I don't think we can do that
okay, so skip this change and keep another.

--
Cheers,
Changbin Du