From: Namhyung Kim Date: Mon, 12 Dec 2022 23:08:20 +0000 (-0800) Subject: perf stat: Do not delay the workload with --delay X-Git-Tag: v6.6.7~3878^2~3 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=c587e77e100fa40eb6af10e00497c67acf493f33;p=platform%2Fkernel%2Flinux-starfive.git perf stat: Do not delay the workload with --delay The -D/--delay option is to delay the measure after the program starts. But the current code goes to sleep before starting the program so the program is delayed too. This is not the intention, let's fix it. Before: $ time sudo ./perf stat -a -e cycles -D 3000 sleep 4 Events disabled Events enabled Performance counter stats for 'system wide': 4,326,949,337 cycles 4.007494118 seconds time elapsed real 0m7.474s user 0m0.356s sys 0m0.120s It ran the workload for 4 seconds and gave the 3 second delay. So it should skip the first 3 second and measure the last 1 second only. But as you can see, it delays 3 seconds and ran the workload after that for 4 seconds. So the total time (real) was 7 seconds. After: $ time sudo ./perf stat -a -e cycles -D 3000 sleep 4 Events disabled Events enabled Performance counter stats for 'system wide': 1,063,551,013 cycles 1.002769510 seconds time elapsed real 0m4.484s user 0m0.385s sys 0m0.086s The bug was introduced when it changed enablement of system-wide events with a command line workload. But it should've considered the initial delay case. The code was reworked since then (in bb8bc52e7578) so I'm afraid it won't be applied cleanly. Fixes: d0a0a511493d2695 ("perf stat: Fix forked applications enablement of counters") Reported-by: Kevin Nomura Signed-off-by: Namhyung Kim Tested-by: Thomas Richter Cc: Adrian Hunter Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Peter Zijlstra Cc: Sumanth Korikkar Link: https://lore.kernel.org/r/20221212230820.901382-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index 2808f2aa..bf640ab 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -539,26 +539,14 @@ static int enable_counters(void) return err; } - if (stat_config.initial_delay < 0) { - pr_info(EVLIST_DISABLED_MSG); - return 0; - } - - if (stat_config.initial_delay > 0) { - pr_info(EVLIST_DISABLED_MSG); - usleep(stat_config.initial_delay * USEC_PER_MSEC); - } - /* * We need to enable counters only if: * - we don't have tracee (attaching to task or cpu) * - we have initial delay configured */ - if (!target__none(&target) || stat_config.initial_delay) { + if (!target__none(&target)) { if (!all_counters_use_bpf) evlist__enable(evsel_list); - if (stat_config.initial_delay > 0) - pr_info(EVLIST_ENABLED_MSG); } return 0; } @@ -926,14 +914,27 @@ try_again_reset: return err; } - err = enable_counters(); - if (err) - return -1; + if (stat_config.initial_delay) { + pr_info(EVLIST_DISABLED_MSG); + } else { + err = enable_counters(); + if (err) + return -1; + } /* Exec the command, if any */ if (forks) evlist__start_workload(evsel_list); + if (stat_config.initial_delay > 0) { + usleep(stat_config.initial_delay * USEC_PER_MSEC); + err = enable_counters(); + if (err) + return -1; + + pr_info(EVLIST_ENABLED_MSG); + } + t0 = rdclock(); clock_gettime(CLOCK_MONOTONIC, &ref_time);