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authorDavid Ahern <dsahern@gmail.com>2013-08-14 08:49:27 -0600
committerArnaldo Carvalho de Melo <acme@redhat.com>2013-08-26 17:25:36 -0300
commit236a3bbd5cb51edbf9550f5a7df885665d18a271 (patch)
tree7e80af39fe66ecc500fb2a3541447f1294a50149 /tools/perf
parentac9be8ee4ecdeae73c78d84ebfe37009e11cf99d (diff)
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>
Diffstat (limited to 'tools/perf')
-rw-r--r--tools/perf/util/machine.c34
-rw-r--r--tools/perf/util/thread.h5
2 files changed, 25 insertions, 14 deletions
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 4514e7e9b659..574feb7003ab 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -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;
}
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 13c62c909392..32d060164b52 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -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);