Messages in this thread | | | Date | Wed, 14 Dec 2022 11:41:14 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf stat: Do not delay the workload with --delay |
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Em Mon, Dec 12, 2022 at 03:08:20PM -0800, Namhyung Kim escreveu: > 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.
Ok, I took up this one instead of Adrian's.
- Arnaldo
> Fixes: d0a0a511493d ("perf stat: Fix forked applications enablement of counters") > Cc: Sumanth Korikkar <sumanthk@linux.ibm.com> > Cc: Thomas Richter <tmricht@linux.ibm.com> > Reported-by: Kevin Nomura <nomurak@google.com> > Signed-off-by: Namhyung Kim <namhyung@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 d040fbcdcc5a..b39bf785a16e 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -540,26 +540,14 @@ 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; > } > @@ -930,14 +918,27 @@ 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); > > -- > 2.39.0.rc1.256.g54fd8350bd-goog
--
- Arnaldo
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