Messages in this thread | | | Subject | Re: [PATCH] perf stat: Improve runtime stat for interval mode | From | kajoljain <> | Date | Mon, 20 Apr 2020 11:18:10 +0530 |
| |
On 4/17/20 6:21 AM, Jin Yao wrote: > 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. > > 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 >
Hi Jin, Thanks for the patch. Was working on similar issue raised by Joakim Zhang. Here's link to my findings: https://lkml.org/lkml/2020/3/24/158
This patch solves the issue.
Acked-By: Kajol Jain <kjain@linux.ibm.com> and Tested-By: Kajol Jain <kjain@linux.ibm.com>
> Now the second 'insn per cycle' and CPI are calculated by the counts > generated in this interval. > > Signed-off-by: Jin Yao <yao.jin@linux.intel.com> > --- > tools/perf/Documentation/perf-stat.txt | 2 ++ > tools/perf/builtin-stat.c | 1 + > tools/perf/util/stat-shadow.c | 5 +++++ > tools/perf/util/stat.h | 1 + > 4 files changed, 9 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 ec053dc1e35c..d5c326ff46d0 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_rt_stat(); > read_counters(&rs); > > if (STAT_RECORD) { > diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c > index 1ad5c5be7e97..c8f5ca6c8749 100644 > --- a/tools/perf/util/stat-shadow.c > +++ b/tools/perf/util/stat-shadow.c > @@ -186,6 +186,11 @@ void perf_stat__reset_shadow_stats(void) > memset(&walltime_nsecs_stats, 0, sizeof(walltime_nsecs_stats)); > } > > +void perf_stat__reset_rt_stat(void) > +{ > + reset_stat(&rt_stat); > +} > + > void perf_stat__reset_shadow_per_stat(struct runtime_stat *st) > { > reset_stat(st); > diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h > index b4fdfaa7f2c0..2975494166dd 100644 > --- a/tools/perf/util/stat.h > +++ b/tools/perf/util/stat.h > @@ -176,6 +176,7 @@ void runtime_stat__init(struct runtime_stat *st); > void runtime_stat__exit(struct runtime_stat *st); > void perf_stat__init_shadow_stats(void); > void perf_stat__reset_shadow_stats(void); > +void perf_stat__reset_rt_stat(void); > void perf_stat__reset_shadow_per_stat(struct runtime_stat *st); > void perf_stat__update_shadow_stats(struct evsel *counter, u64 count, > int cpu, struct runtime_stat *st); >
| |