Messages in this thread | | | From | Arnaldo Carvalho de Melo <> | Date | Thu, 23 Apr 2020 10:44:14 -0300 | Subject | Re: [PATCH v2] perf stat: Improve runtime stat for interval mode |
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Em Wed, Apr 22, 2020 at 08:53:41AM +0800, Jin, Yao escreveu: > Hi Arnaldo, > > On 4/21/2020 9:53 PM, Arnaldo Carvalho de Melo wrote: > > 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? > > > > Yes, should use "too" here. :) > > > 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 > > > > I have tried to find the patch which introduced this issue. > > 51fd2df1e882 ("perf stat: Fix interval output values"). > > This patch zeros stats for interval mode. I just think it should reset > rt_stat too.
> But I really don't know if it's fair to this patch so I don't add it in my > patch description.
I think you are right that 51fd2df1e882 patch missed the fix you're providing now, so I think it is fair to say that your current patch fixes 51fd2df1e882, so I added it in the Fixes tag for the patch discussed in this message, thanks.
- Arnaldo
> Thanks > Jin Yao > > > > 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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