On 02/08/13 06:52, David Ahern wrote: > Occassionally events (e.g., context-switch, sched tracepoints) are losing > the conversion of sample data associated with a thread. For example: > > $ perf record -e sched:sched_switch -c 1 -a -- sleep 5 > $ perf script > <selected events shown> > ls 30482 [000] 1379727.583037: sched:sched_switch: prev_comm=ls > prev_pid=30482 ... > ls 30482 [000] 1379727.586339: sched:sched_switch: prev_comm=ls > prev_pid=30482 ... > :30482 30482 [000] 1379727.589462: sched:sched_switch: prev_comm=ls > prev_pid=30482 ... > > The last line lost the conversion from tid to comm. If you look at the events > (perf script -D) you see why - SAMPLE event is generated after the EXIT: > > 0 1379727589449774 0x1540b0 [0x38]: > PERF_RECORD_EXIT(30482:30482):(30482:30482) > 0 1379727589462497 0x1540e8 [0x80]: PERF_RECORD_SAMPLE(IP, 1): 30482/30482: > 0xffffffff816416f1 period: 1 addr: 0 > ... thread: :30482:30482 > > When perf processes the EXIT event the thread is moved to the dead_threads > list. When the SAMPLE event is processed no thread exists for the pid so a new > one is created by machine__findnew_thread. > > This patch address the problem by delaying the move to the dead_threads list > until the tid is re-used (per Adrian's suggestion). > > With this patch we get the previous example shows: > > ls 30482 [000] 1379727.583037: sched:sched_switch: prev_comm=ls > prev_pid=30482 ... > ls 30482 [000] 1379727.586339: sched:sched_switch: prev_comm=ls > prev_pid=30482 ... > ls 30482 [000] 1379727.589462: sched:sched_switch: prev_comm=ls > prev_pid=30482 ... > > and > > 0 1379727589449774 0x1540b0 [0x38]: > PERF_RECORD_EXIT(30482:30482):(30482:30482) > 0 1379727589462497 0x1540e8 [0x80]: PERF_RECORD_SAMPLE(IP, 1): 30482/30482: > 0xffffffff816416f1 period: 1 addr: 0 > ... thread: ls:30482 > > v3: re-do from a time based check to a delayed move to dead_threads list > > v2: Rebased to latest perf/core branch. Changed time comparison to use > a macro which explicitly shows the time basis > > Signed-off-by: David Ahern <[email protected]> > Cc: Frederic Weisbecker <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Jiri Olsa <[email protected]> > Cc: Mike Galbraith <[email protected]> > Cc: Namhyung Kim <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Stephane Eranian <[email protected]> > Cc: Adrian Hunter <[email protected]> > ---
This has the side-effect of leaving more threads on machine->threads, which seems OK to me. So: Acked-by: Adrian Hunter <[email protected]> > tools/perf/util/machine.c | 37 +++++++++++++++++++------------------ > 1 file changed, 19 insertions(+), 18 deletions(-) > > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c > index f9f9d63..0d29b1b 100644 > --- a/tools/perf/util/machine.c > +++ b/tools/perf/util/machine.c > @@ -994,11 +994,27 @@ out_problem: > return 0; > } > > +static void machine__remove_thread(struct machine *machine, struct thread > *th) > +{ > + machine->last_match = NULL; > + rb_erase(&th->rb_node, &machine->threads); > + /* > + * We may have references to this thread, for instance in some > hist_entry > + * instances, so just move them to a separate list. > + */ > + list_add_tail(&th->node, &machine->dead_threads); > +} > + > int machine__process_fork_event(struct machine *machine, union perf_event > *event) > { > - struct thread *thread = machine__findnew_thread(machine, > event->fork.tid); > + struct thread *thread = machine__find_thread(machine, event->fork.tid); > struct thread *parent = machine__findnew_thread(machine, > event->fork.ptid); > > + /* if a thread currently exists for the thread id remove it */ > + if (thread != NULL) > + machine__remove_thread(machine, thread); > + > + thread = machine__findnew_thread(machine, event->fork.tid); > if (dump_trace) > perf_event__fprintf_task(event, stdout); > > @@ -1011,27 +1027,12 @@ int machine__process_fork_event(struct machine > *machine, union perf_event *event > return 0; > } > > -static void machine__remove_thread(struct machine *machine, struct thread > *th) > -{ > - machine->last_match = NULL; > - rb_erase(&th->rb_node, &machine->threads); > - /* > - * We may have references to this thread, for instance in some > hist_entry > - * instances, so just move them to a separate list. > - */ > - list_add_tail(&th->node, &machine->dead_threads); > -} > - > -int machine__process_exit_event(struct machine *machine, union perf_event > *event) > +int machine__process_exit_event(struct machine *machine __maybe_unused, > + union perf_event *event) > { > - struct thread *thread = machine__find_thread(machine, event->fork.tid); > - > if (dump_trace) > perf_event__fprintf_task(event, stdout); > > - if (thread != NULL) > - machine__remove_thread(machine, thread); > - > return 0; > } > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
