From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757219Ab3HBDwj (ORCPT ); Thu, 1 Aug 2013 23:52:39 -0400 Received: from mail-pa0-f42.google.com ([209.85.220.42]:44775 "EHLO mail-pa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753019Ab3HBDwh (ORCPT ); Thu, 1 Aug 2013 23:52:37 -0400 From: David Ahern To: acme@ghostprotocols.net, linux-kernel@vger.kernel.org Cc: David Ahern , Frederic Weisbecker , Ingo Molnar , Jiri Olsa , Mike Galbraith , Namhyung Kim , Peter Zijlstra , Stephane Eranian , Adrian Hunter Subject: [PATCH] perf: sample after exit loses thread correlation - v3 Date: Thu, 1 Aug 2013 21:52:31 -0600 Message-Id: <1375415551-62625-1-git-send-email-dsahern@gmail.com> X-Mailer: git-send-email 1.7.10.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 - 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 Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mike Galbraith Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Adrian Hunter --- 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; } -- 1.7.10.1