The following commit has been merged into the perf/core branch of tip: Commit-ID: 197ba86fdc888dc0d3d6b89b402c9c6851d4c6fb Gitweb: https://git.kernel.org/tip/197ba86fdc888dc0d3d6b89b402c9c6851d4c6fb Author: Jin Yao <yao.jin@xxxxxxxxxxxxxxx> AuthorDate: Mon, 20 Apr 2020 22:54:17 +08:00 Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> CommitterDate: Thu, 23 Apr 2020 11:03:46 -03:00 perf stat: Improve runtime stat for interval mode For interval mode, the metric is printed after the '#' character if it exists. But it's not calculated by the counts generated in this interval. See the 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 mode, the 'rt_stat' variable should be reset too. 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@xxxxxxxxxxxxxxx> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> Tested-By: Kajol Jain <kjain@xxxxxxxxxxxxx> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx> Cc: Jin Yao <yao.jin@xxxxxxxxx> Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: http://lore.kernel.org/lkml/20200420145417.6864-1-yao.jin@xxxxxxxxxxxxxxx Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> --- 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 4d56586..3fb5028 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 9207b6c..3f050d8 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) {
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