From: Namhyung Kim namhyung@kernel.org
[ Upstream commit c587e77e100fa40eb6af10e00497c67acf493f33 ]
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 nomurak@google.com Signed-off-by: Namhyung Kim namhyung@kernel.org Tested-by: Thomas Richter tmricht@linux.ibm.com Cc: Adrian Hunter adrian.hunter@intel.com Cc: Ian Rogers irogers@google.com Cc: Ingo Molnar mingo@kernel.org Cc: Jiri Olsa jolsa@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Sumanth Korikkar sumanthk@linux.ibm.com Link: https://lore.kernel.org/r/20221212230820.901382-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/builtin-stat.c | 33 +++++++++++++++++---------------- 1 file changed, 17 insertions(+), 16 deletions(-)
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index 2602c750779d..aad65c95c371 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -558,26 +558,14 @@ 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; } @@ -953,14 +941,27 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx) 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);