Messages in this thread | | | From | Arnaldo Carvalho de Melo <> | Date | Tue, 21 Apr 2020 10:53:29 -0300 | Subject | Re: [PATCH v2] perf stat: Improve runtime stat for interval mode |
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Em Mon, Apr 20, 2020 at 10:54:17PM +0800, Jin Yao escreveu: > For interval mode, the metric is printed after # if it exists. But > it's not calculated by the counts generated in this interval. See > following examples, > > root@kbl-ppc:~# perf stat -M CPI -I1000 --interval-count 2 > # time counts unit events > 1.000422803 764,809 inst_retired.any # 2.9 CPI > 1.000422803 2,234,932 cycles > 2.001464585 1,960,061 inst_retired.any # 1.6 CPI > 2.001464585 4,022,591 cycles > > The second CPI should not be 1.6 (4,022,591/1,960,061 is 2.1) > > root@kbl-ppc:~# perf stat -e cycles,instructions -I1000 --interval-count 2 > # time counts unit events > 1.000429493 2,869,311 cycles > 1.000429493 816,875 instructions # 0.28 insn per cycle > 2.001516426 9,260,973 cycles > 2.001516426 5,250,634 instructions # 0.87 insn per cycle > > The second 'insn per cycle' should not be 0.87 (5,250,634/9,260,973 is 0.57). > > The current code uses a global variable rt_stat for tracking and > updating the std dev of runtime stat. Unlike the counts, rt_stat is > not reset for interval. While the counts are reset for interval. > > perf_stat_process_counter() > { > if (config->interval) > init_stats(ps->res_stats); > } > > So for interval, the rt_stat should be reset either.
s/either/too/g right?
And please try and find what was the cset that introduced the problem, so that we can have a Fixes: line and the stable series can pick it, ok?
- Arnaldo
> This patch resets rt_stat before read_counters, so the runtime > stat is only calculated by the counts generated in this interval. > > With this patch, > > root@kbl-ppc:~# perf stat -M CPI -I1000 --interval-count 2 > # time counts unit events > 1.000420924 2,408,818 inst_retired.any # 2.1 CPI > 1.000420924 5,010,111 cycles > 2.001448579 2,798,407 inst_retired.any # 1.6 CPI > 2.001448579 4,599,861 cycles > > root@kbl-ppc:~# perf stat -e cycles,instructions -I1000 --interval-count 2 > # time counts unit events > 1.000428555 2,769,714 cycles > 1.000428555 774,462 instructions # 0.28 insn per cycle > 2.001471562 3,595,904 cycles > 2.001471562 1,243,703 instructions # 0.35 insn per cycle > > Now the second 'insn per cycle' and CPI are calculated by the counts > generated in this interval. > > v2: > --- > Use just existing perf_stat__reset_shadow_per_stat(&rt_stat). > We don't need to define new function perf_stat__reset_rt_stat. > > Signed-off-by: Jin Yao <yao.jin@linux.intel.com> > --- > tools/perf/Documentation/perf-stat.txt | 2 ++ > tools/perf/builtin-stat.c | 1 + > 2 files changed, 3 insertions(+) > > diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt > index 4d56586b2fb9..3fb5028aef08 100644 > --- a/tools/perf/Documentation/perf-stat.txt > +++ b/tools/perf/Documentation/perf-stat.txt > @@ -176,6 +176,8 @@ Print count deltas every N milliseconds (minimum: 1ms) > 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' > > +If the metric exists, it is calculated by the counts generated in this interval and the metric is printed after #. > + > --interval-count times:: > Print count deltas for fixed number of times. > This option should be used together with "-I" option. > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index 9207b6c45475..3f050d85c277 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -359,6 +359,7 @@ static void process_interval(void) > clock_gettime(CLOCK_MONOTONIC, &ts); > diff_timespec(&rs, &ts, &ref_time); > > + perf_stat__reset_shadow_per_stat(&rt_stat); > read_counters(&rs); > > if (STAT_RECORD) { > -- > 2.17.1 >
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- Arnaldo
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