perf tools: Sample after exit loses thread correlation
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 - a 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 v4: per Arnaldo's request add dead flag to thread struct and set when task exits 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 <dsahern@gmail.com> Acked-by: Adrian Hunter <adrian.hunter@intel.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/r/1376491767-84171-1-git-send-email-dsahern@gmail.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
parent
ac9be8ee4e
commit
236a3bbd5c
|
@ -1031,11 +1031,27 @@ 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);
|
||||
|
||||
|
@ -1048,18 +1064,8 @@ 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);
|
||||
|
||||
|
@ -1067,7 +1073,7 @@ int machine__process_exit_event(struct machine *machine, union perf_event *event
|
|||
perf_event__fprintf_task(event, stdout);
|
||||
|
||||
if (thread != NULL)
|
||||
machine__remove_thread(machine, thread);
|
||||
thread__exited(thread);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
|
@ -16,6 +16,7 @@ struct thread {
|
|||
pid_t ppid;
|
||||
char shortname[3];
|
||||
bool comm_set;
|
||||
bool dead; /* if set thread has exited */
|
||||
char *comm;
|
||||
int comm_len;
|
||||
|
||||
|
@ -26,6 +27,10 @@ struct machine;
|
|||
|
||||
struct thread *thread__new(pid_t tid);
|
||||
void thread__delete(struct thread *self);
|
||||
static inline void thread__exited(struct thread *thread)
|
||||
{
|
||||
thread->dead = true;
|
||||
}
|
||||
|
||||
int thread__set_comm(struct thread *self, const char *comm);
|
||||
int thread__comm_len(struct thread *self);
|
||||
|
|
Loading…
Reference in a new issue