From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754953Ab3HEIXu (ORCPT ); Mon, 5 Aug 2013 04:23:50 -0400 Received: from mga03.intel.com ([143.182.124.21]:12656 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754585Ab3HEIXq (ORCPT ); Mon, 5 Aug 2013 04:23:46 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.89,817,1367996400"; d="scan'208";a="376249926" Message-ID: <51FF6276.3050507@intel.com> Date: Mon, 05 Aug 2013 11:29:42 +0300 From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: David Ahern CC: acme@ghostprotocols.net, linux-kernel@vger.kernel.org, Frederic Weisbecker , Ingo Molnar , Jiri Olsa , Mike Galbraith , Namhyung Kim , Peter Zijlstra , Stephane Eranian Subject: Re: [PATCH] perf: sample after exit loses thread correlation - v3 References: <1375415551-62625-1-git-send-email-dsahern@gmail.com> In-Reply-To: <1375415551-62625-1-git-send-email-dsahern@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > > 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 > --- This has the side-effect of leaving more threads on machine->threads, which seems OK to me. So: Acked-by: 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; > } > >