Messages in this thread Patch in this message | | | From | Jin Yao <> | Subject | [PATCH] perf stat: Improve runtime stat for interval mode | Date | Fri, 17 Apr 2020 08:51:54 +0800 |
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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
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); -- 2.17.1
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