From 236a3bbd5cb51edbf9550f5a7df885665d18a271 Mon Sep 17 00:00:00 2001 From: David Ahern Date: Wed, 14 Aug 2013 08:49:27 -0600 Subject: [PATCH] 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 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 Acked-by: Adrian Hunter Cc: Adrian Hunter Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mike Galbraith Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Link: http://lkml.kernel.org/r/1376491767-84171-1-git-send-email-dsahern@gmail.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/machine.c | 34 ++++++++++++++++++++-------------- tools/perf/util/thread.h | 5 +++++ 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); -- 2.39.5