Messages in this thread Patch in this message | | | Date | Tue, 6 Feb 2018 15:48:20 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 01/17] perf report: Ask ordered events for --tasks option |
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Em Tue, Feb 06, 2018 at 07:17:57PM +0100, Jiri Olsa escreveu: > If we have the time in, keep the events in time order.
Try to be more verbose, what actual effect this will have in this particular case?
So, I had to try it to see the effects and explain them:
--- /tmp/before 2018-02-06 15:40:29.536411625 -0300 +++ /tmp/after 2018-02-06 15:40:51.963403599 -0300 @@ -5,34 +5,34 @@ 2540 2540 1818 | gnome-terminal- 3489 3489 2540 | bash 32433 32433 3489 | perf - 32434 32434 32433 | perf + 32434 32434 32433 | make 32441 32441 32434 | make 32514 32514 32441 | make 511 511 32514 | sh - 512 512 511 | sh + 512 512 511 | install
We don't have perf calling perf calling make, etc, the second perf actually is 'make', i.e. there was reordering of PERF_RECORD_COMM/PERF_RECORD_FORK:
Look for FORK and COMM meta events, for those tids:
[root@jouet acme]# perf report -D | egrep 'PERF_RECORD_(FORK|COMM)' | egrep '3243[34]' 0 14774650990679 0x1a3cd8 [0x38]: PERF_RECORD_FORK(32433:32433):(3489:3489) 1 14774652080381 0x1d6568 [0x30]: PERF_RECORD_COMM exec: perf:32433/32433 1 14774742473340 0x1dbb48 [0x38]: PERF_RECORD_FORK(32434:32434):(32433:32433) 0 14774752005779 0x1a4af8 [0x30]: PERF_RECORD_COMM exec: make:32434/32434 0 14774753997960 0x1a5578 [0x38]: PERF_RECORD_FORK(32435:32435):(32434:32434) 0 14774756070782 0x1a5618 [0x38]: PERF_RECORD_FORK(32438:32438):(32434:32434) 0 14774757772939 0x1a5680 [0x38]: PERF_RECORD_FORK(32440:32440):(32434:32434) 0 14774758230600 0x1a56e8 [0x38]: PERF_RECORD_FORK(32441:32441):(32434:32434) [root@jouet acme]#
So they are on different CPUs, thus ring buffers, and when we don't use ordered_events, we end up mixing that up, right?
- Arnaldo > Link: http://lkml.kernel.org/n/tip-3wcrngoibk5l96nqyhp0nbkm@git.kernel.org > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > --- > tools/perf/builtin-report.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c > index 4ad5dc649716..8ef71669e7a0 100644 > --- a/tools/perf/builtin-report.c > +++ b/tools/perf/builtin-report.c > @@ -614,6 +614,7 @@ static int stats_print(struct report *rep) > static void tasks_setup(struct report *rep) > { > memset(&rep->tool, 0, sizeof(rep->tool)); > + rep->tool.ordered_events = true; > if (rep->mmaps_mode) { > rep->tool.mmap = perf_event__process_mmap; > rep->tool.mmap2 = perf_event__process_mmap2; > -- > 2.13.6
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